A simple bump on the head can kill you

Just beneath this thin bit of skull is the middle meningeal artery, between the skull and the dura. If you get clonked in the temple, this artery can rupture.

Which is totally what happened to Chekhov in Star Trek IV.

. . . what?

I thought they put creatures in his body...

Oh, wait, that was II...GEEK FAIL

I hit some bad ice while out skating on a pond and went down fast on my back, bouncing the back of my head off the ice. I was a little dazed but didn't black out. I slept a lot for two days. Had a headache x 1 week. And for 2-3 weeks I had this strange disequilibrium --a bit like the start of lightheadedness. It came and went unpredictably, lasting a few seconds when it happened. I mentioned it to a neurologist friend, who said it was likely an inner ear problem that should go away gradually.

I think it has. Haven't noticed it for a few days now.

I feel I can't remember what I'm doing or what I want to say. Maybe this is nothing new. Maybe I'm paying attention to my brain more and talking myself into having symptoms.

Helmets and seatbelts always. I'm not going to be lazy about that anymore.

PalMD, please enlighten us as to what is "markedly abnormal" about the brain in the first picture. Aside from, you know, being open :)

Ah, yeah...

IIRC, it is covered in small hemorrhages from pneumococcal meningitis...

There are still housewives who in a fit of anger will slam a frying pan or rolling pin down on her kid's crown.

Back when doctors made house calls, ensuing deaths were attributed to 'brain fever', and the police never interfered. Those surviving with brain injuries would always have a story to explain X-rays of old fractures.

Today I don't know how such brain injuries and deaths are handled, but I do know the media never report them.

When engaging in activities in which head trauma is a significant risk (biking, skiing, etc.) a helmet can absorb a good deal of the energy of a blow so that your brain doesn't have to.

Welcome to my turf, Doctor. I profoundly hope you don't see as many primary concussions in a year as I do (and would, thank you, much rather not.) Unfortunately, your statement above is a great guide to behavior (I wear a helmet when skiing, for instance) but not quite accurate technically.

The fact is that a helmet is very good protection against penetrating injuries and against high-velocity, low-impulse blunt trauma -- the kind you get whacking your head against a curb, for instance, or from the skillet. Alas, it is not that much help against the kind of deceleration trauma currently in the news.

The reason is that there's a fundamental difference in mechanism of injury between the two. Getting thumped in the chest at 15 kph by a softball hurts -- but running into a wall chest-first at 15 kph can result in a fatal aortal tear due to ligamental rupture and the heart "flying" loose in the low density of the thoracic cavity. It's happened at speeds as low as 7 mph.

Likewise, having something fall six feet onto your head can hurt; we assume the worst and take precautions against cerebrospinal injuries because something that whacks your head enough to rattle you has the potential to do Bad Things to your cervical vertebrae. On the other hand, falling six feet to hit your head on a floor can do a lot more, because then the brain is decelerating at lotsagees against the interior of the skull. Alas, cerebrospinal fluid is not the same density as the brain itself.

Which is where the helmet comes in.

Obviously, a steel helmet is good protection against penetrating injury and absolutely none whatever against deceleration trauma because it can't absorb any energy. A helmet with an energy-absorbing liner does, but only until it runs out of "crush space" -- which is no greater than the liner thickness and in practice much less. This is where we turn to physics; those who cannot abide quantitative analysis are advised to skip the rest of this post.

When your head decelerates by striking a hard surface, the brain decelerates almost but not instantaneously inside the skull. In practice, it deforms a bit and that spreads out the deceleration. Also, the deceleration experienced by the brain is mitigated by the (approximate) matching between the density of the brain and CSF, but the brain is denser by about 3% [1]. As a result, when the head undergoes a 30g stop, the brain suffers about a 1g load. Which is Not A Good Thing, since it's not exactly rugged. However, 30 gravities is survivable; it's what people routinely walk away from in car wrecks with seatbelts and airbags (although these are mitigated by movement of the head on the neck.)

So what kind of decelerations does a helmeted head experience?

If your head falls five feet to a hard floor while wearing a WonderFoam helmet ten cm thick, you're looking at 60 inches at one gravity acceleration and four inches at 15 gravities deceleration. Assuming you're wearing a ten-cm foam helmet, anyway. Ski down a 20% slope for thirty feet, biff, and smack your head and you've wound up 132 inches of vertical at one gravity but stopped in less than an inch of helmet foam, for a deceleration of 132 gravities. That's Not Good, because it means that the 40-some ounces of brain have been exposed to forces of (40 oz)(132)/(30) or about 11 pounds force.

Those who have actually handled brain tissue (I haven't, thank you) can tell you what happens when ten-plus pounds force are applied to one. Not good.

I have, however, worked an on-hill fatality with similar mechanism. The patient was a snowboarder who basically caught an edge and did a faceplant at speed. The snow was, in fact, quite soft and he made a hole in it much deeper than any helmet could ever be -- but he never regained consciousness. Our report from Barrows Neurological Center (where we flew him) was that rather as expected: the impact had more or less turned his forebrain to mush on impact.

The statistics are that helmets do a very good job of reducing minor head injuries. You would not believe the self-inflicted wounds I see with snowboarders, including lacerations to the crowns of their own heads from their boards' edges. I kid you not. Helmets are wonderful for those, and frankly they're also much better at keeping your head warm in variable weather. I love them.

However, those same statistics tell us that helmets don't reduce severe head injuries at all. That's just the way it is. So, in all seriousness, my advice is to wear both helmets and (for snowboarders) wrist braces. If a snowboarder can't afford both, wear the wrist braces because broken wrists are absolutely the most common injury I see, and braces are very good protection against them. I'd cut my on-hill injuries in half if snowboarders only wore the things.

Best of all: ski safe. When in doubt, fall down.

Lots of really great information on snow-sports safety at http://www.ski-injury.com/

[1] My sources are very old -- could one of the more medically knowledgable correct this?

Thank you SO much, DC for the terrific analysis. Since I added helmets as an afterthought, i didn't research the topic. I very much appreciate the update.

Links to good studies:

http://ski-injury.com/prevention/helmet Good general discussion

http://www.cpsc.gov/library/skihelm.pdf Somewhat alarmist discussion.

http://www.ama-assn.org/ama/no-index/about-ama/13646.shtml AMA report on helmets and why they wouldn't work. Skiers are traveling faster than bicycle speed by quite a bit.

Back when I was a student, the prospect of free food lured me to a presentation on modeling what happens when the head has to decelerate quickly.

If I recall correctly, frequently the most damage to the brain is opposite from the point of impact, because the cerebral fluid is denser than the brain, has greater inertia, and so rushes forward, squeezing the brain against the (usually) back of the skull.

The computer model being demonstrated featured an oval brain inside a rectangular skull, all 2D. I'm not sure how much the lack of tight fitting and much greater volume of cerebral fluid would affect the accuracy of the model.

Thanks for this article and the helpful comments. I'm not a health care professional, so forgive me if my questions are obvious. First, on the CT scan showing the epidural hematoma: is this an image of someone irreversibly injured? I mean, if you look at this film, do you know you're seeing an injury that cannot be survived?

Second, Ms. Richardson's emergency developed quickly, despite her initial walking & talking. (I know of a similar event, years ago, with an acquaintance who fell off a horse, was walking & talking, was admitted, fell out of his hospital bed, possibly adding to his injury, and then died.) Is this type of injury almost always fatal? Presumably someone like Ms. Richardson, whose ability to pay for the best care was clearly not an issue, would have had as good a chance as anyone. But this went horrible so fast. She'd have had to undergo emergency surgery shortly after complaining of the headache and feeling unwell. What are the odds of anyone getting care so quickly?

Wow DC, That was a great explanation! I had read somewhere before (I don't remember where) that CSF was denser than brain tissue, hence impacts to the front of the head often resulted in injuries to the back of the brain (as the CSF deccellerated faster and pushed the brain back). I'm guessing that was bad information.

Also, it seems that Ms. Richardson has died. That's a real shame.

I had read somewhere before (I don't remember where) that CSF was denser than brain tissue, hence impacts to the front of the head often resulted in injuries to the back of the brain (as the CSF deccellerated faster and pushed the brain back). I'm guessing that was bad information.

It's entirely possible that your information on relative density is in fact better than mine. All I've been able to find is links to work behind paywalls, so my main sources are out-of-copyright. In other words, really old.

However, I was taught that coup/countercoup injuries were from rebound, not from initial brain/cranium impact being opposite the source of injury.

Is this type of injury almost always fatal?

No. However, let's distinguish between the "mechanism of injury" and the actual tissue trauma.

I've seen hundreds of what were probably concussions [1] over the years; this year I've seen more than ten in one day. We must have been having a special or something. To the best of my knowledge, every single one of them was examined and released, including the ones we helicoptered to regional trauma centers.

The reason we play it that safe is simple: if we don't, eventually the odds will catch up with us and we'll end up with a dead patient. We don't want that.

Presumably someone like Ms. Richardson, whose ability to pay for the best care was clearly not an issue, would have had as good a chance as anyone. But this went horrible so fast. She'd have had to undergo emergency surgery shortly after complaining of the headache and feeling unwell. What are the odds of anyone getting care so quickly?

There is what we call the "golden hour," where for a while the human body compensates for injury pretty well, and then heads downhill in a hurry. There's a nasty cycle involved with closed-head injuries that is pretty easy to deal with if you catch it early and a stone bitch if you wait.

What happens is that a brain injury starts to swell. Nothing special yet, but as it swells it increases intracranial pressure. This interferes with circulation and reduces oxygen perfusion to the brain, which the body attempts to compensate for by cranking up blood pressure. The increased blood pressure unfortunately increases swelling.

Positive feedback. After a while, you can get lots of nasties such as a cerebral aneurism, general loss of perfusion leading to brain death, stuff like that. That's apparently what happened in the instant case.

If you recognize early that there's been a closed-head injury, the first order of business is to get the patient to (a)rest, and (b) put them on high-flow oxygen to improve perfusion and head off that cycle [2]. Then we transport them so that we don't waste that "golden hour." Head injury cases should be in Radiology as soon as possible, precisely because early intervention is the best chance they have in the rare case of the uglies such as a subdural hematoma.

Note that my ski area is more than a half-hour by ambulance from the nearest town. It takes a minimum of a half-hour for either an ambulance or a helicopter to arrive, so the on-scene judgment calls can get a bit tense. We haven't screwed the pooch -- yet.

This is where the science comes in, because we don't have enough personal experience with the really bad ones to go on. Our rule is that A&Ox1 flies, A&Ox3 rolls, and in between is a pucker. I've shipped two kids this year who were actually A&Ox4 but were "just not right" according to people who knew them -- and haven't been chewed out by the ER attending (or the families) yet.

However, there's nothing we can do if we don't get asked to begin with -- which is, apparently, what happened this time.

[1] I am not a physician, I don't play one on the Internet, and I damn well don't play one on the ski slopes. "Concussion" is a diagnosis. Non-physicians don't diagnose -- but we have to make judgment calls anyway. Therefore, they may well have been concussions -- and that's how we had to treat them.
[2] We also enforce rest by the simple expedient of strapping them to a backboard. Hard to do much then, although that's not why we do it.

Not surprisingly, head injuries are also common in equestrian sports. I used to play polo several times a week, and even if you have the best polo helmet available, I don't think it's much protection against the deceleration-induced coup contrecoup brain injury that's been mentioned.

However, a helmet designed for polo is great protection if you get hit with a mallet or a ball, and also to some extent if you end up under your horse's hooves or body. The macho players will not put a protective face guard on their helmets, and as a consequence, there are a fair number of one-eyed or partially-sighted polo players. The polo ball is high density plastic, and a top player can reliably hit the ball such that it travels at speeds of 100 mph+ ... so you can just imagine what it might do to an eye or to the facial skeleton and teeth. Many of the helmets don't adequately protect the pterion point that PalMD mentioned, and I've seen one player hit in the temple with a penalty shot, which knocked him right off his horse. Fortunately, no epidural hematoma.

[1] is a paper from 1996 that gives the density of CSF as 1.0003 - 1.0007 g/ml, while according to a number of papers postdating 2000 (e.g. [2]), the density of brain tissue is around 1.05 g/ml.

The presentation I saw was probably in 2005.

[1] is a paper from 1996 that gives the density of CSF as 1.0003 - 1.0007 g/ml, while according to a number of papers postdating 2000 (e.g. [2]), the density of brain tissue is around 1.05 g/ml.

Thanks, mds.

That makes my 30:1 derating a bit optimistic; it should be more like 23:1 or so. It doesn't really change the conclusion, since I wasn't being precise about the amount of force required to damage tissues but I do like to nail down (ewwww!) as many factors as possible.

Thanks mds!

Rereading:

At first, the injured person may feel fine, but as the blood accumulates, the patient develops a headache, and rapidly becomes unconscious and dies

Don't bet on the headache. Lack of a headache is by no means an indication of safety.

There are lots of other "declining mental status" indicators to watch out for: vision disturbances, sleepiness, mood changes, combativeness, perseveration (my favorite), altered pupil response, ... It's quite a list.

In borderline cases, our practice is to have someone who knows the patient stay with hir and talk -- a lot. Changes that we wouldn't notice will be apparent to a friend or family member. I mentioned transporting a couple of kids this year who were A&Ox4 -- well, that was because they:
(a) had mechanism,
(b) reported not feeling "right," and
(c) had family members who described their behavior as atypical and worrisome.

I heard back from one -- radiology confirmed a concussion, but nothing requiring treatment. Where head injuries are concerned, I like being told I was taking precautions against something that didn't turn up.

It's also very common for patients who need treatment most to be least amenable to accepting it (which appears to be what happened in Ms. Richardson's case.) I transported a patient this year who was A&Ox3, had a broken helmet, whose wife said he was acting very atypical, who was perseverating, and who, while strapped to a backboard, was telling us that he could drive himself to the hospital. (Another radiological examine-and-release. Love them!) Urk!

Without a family member present to exercise some influence, I can so easily see Ms. Richardson refusing treatment -- and that's no reflection on her normal mental processes.

For good or ill, we have to presume patient competence unless we have profound reasons to the contrary. There's a subject for you and Dr. Stemwedel, PAL.

A few points, based on my life downstream in rehabilitation.
We're seeing more patients now with large craniectomies, after stroke or traumatic bleeds, and this seems to be helpful - but again, it needs to be done fairly quickly. I'll be interested to read the follow-up reports, and see what was done (and not done) for Ms. Richardson. Otherwise, these 'talk and die' injuries, although rare, will be catastrophic.

Occasionally, patients will have a very slow subdural, and may bleed and slowly deteriorate for several weeks, before they turn up at the emergency room, often conscious but with decreased orientation. They seem to be the ones who often show the worst self-awareness (which maes sense, because they've been deteriorating for a while before seeking help), and my have more frontal bleeds, rather than lateral/parietal.
In the end, time is brain.
Dr. Benway - see your family doctor regularly for the first 3 weeks after a concussion, check with your family/friends, and follow strategies to limit overexertion for the first few weeks. A number of areas have 'concussion clinics', for information and suggestions early after concussion. Here's a good online, and use their patient information sheet. resource:http://www.vch.ca/abi/erbis.htm

Here in Australia, helmets have been compulsory for cyclists for about 30 years. I've been wearing one whenever I ride for 35 years. The statistics for cyclists here are that 70% of cyclists admitted to hospital have head injuries and helmets prevent 70% of (hospital admissible) cyclist head injuries, so a helmet more than halves your chances of being admitted to hospital. Fortunately cyclist deaths are too rare here to get reliable statistics about death and helmets.

When cycling or skating, the helmet is generally addressing the fall from one body height, while the horizontal speed is dissipated in a skid, costing skin but not brain.

davidp: Do you have references for those statistics? That latter figure especially seems like a "how exactly are they supposed to tell?" figure: If you know that cycle helmets prevent 70% of injuries, then you must therefore know the counterfactual number of injuries that there would have been without the helmets being present. You can do case/control group studies of course, but they're notorious for being difficult to carry out accurately because of the strong confounding factors surrounding helmet wearing.

When cycling or skating, the helmet is generally addressing the fall from one body height, while the horizontal speed is dissipated in a skid, costing skin but not brain.

Unless one runs into a kerb or other stationary object, at which point we're back to the benefits of spreading the impact. Helmet linings aren't really energy absorbers so much as a compliant layer which guards against force concentrations.

Ski injuries are different in that:
(a) there are fewer vertical stationary obstacles, and
(b) there are more mechanisms for translating horizontal momentum to vertical.

Among the latter is the famous "catching an edge," which results in the body rotating around the edge, transferring whole-body kinetic energy to the head in particular. Sort of like cracking a whip, a 30 kph horizontal velocity can end up as a 60 kph vertical impact of head on snow.

The forces that can result in bilateral silver fork fractures [1] are more than sufficient to turn grey matter into marmalade.

[1] Distal fractures of both the radius and ulna with upward angulation, resulting in the hand taking a "drop" at the wrist. The net effect resembles a silver fork.

We're just going through some of this now with a family member who fell on her head. Ambulance was there in 5 minutes but the trauma center was 20-30 minutes away. They did an immediate cat scan and then another in a couple hours, increased oxygen, and everything I read in an article in MDConsult that you're supposed to do. It was a coup-contrecoup thing - the main issue was on the side opposite of the impact. When the bleeding didn't stop and there was a midline shift, unequal pupil dilation, etc., they did a crainiotomy and applied some hemostatic compound.... we were really lucky. There's aphasia and other issues, but still.

DC, thanks for addressing my questions. It's a reminder to me that in case of emergency - even if the emergency doesn't seem to be all that emergent - I'm going to have to overcome all my usual tendencies to being compliant and non-confrontational and insist on getting someone to the hospital. I hate to say it, but I simply loathe being scolded or yelled at, and that inhibition is certainly not what you want in a first, second, third or even last-responder.

This is the effective attitude to have: "...I heard back from one -- radiology confirmed a concussion, but nothing requiring treatment. Where head injuries are concerned, I like being told I was taking precautions against something that didn't turn up...."

but your profession would chew me up and spit me out in far less than an hour. I just haven't got the psychological wherewithal.

As a roller blader on city streets (usually early in the morning before traffic builds up), I always wear wrist and knee guards and a helmet, but it's a bicycling helmet. I do go fairly fast, I estimate 10-15 MPH. Is there a better type of helmet to wear? Richardson's injury and death has really made me rethink this activity altogether, as I'm middle-aged and a mother of two.

I hate to say it, but I simply loathe being scolded or yelled at, and that inhibition is certainly not what you want in a first, second, third or even last-responder.

You might be surprised -- necessity has a way of brining out the inner Jewish Mother in us all.

This is the effective attitude to have: "...I heard back from one -- radiology confirmed a concussion, but nothing requiring treatment. Where head injuries are concerned, I like being told I was taking precautions against something that didn't turn up...."

I have hopes that the (very) public story of Ms. Richardson will turn out to save others' lives by her example of what can happen along Rivers in Egypt.

This is a great read! I sorta wish this info was available for a more objective article when a few weeks ago (and currently as they move slow) somebody was trying to get aluminum bats banned from little league ball in Chicago using statistics that were pulled out of an unknown place resulting in an alderman doing the same almost. While it's good to be more proactive in protection, it's hard to see the line when many of us grew up swinging from ropes strung from a rail in the loft of a barn over a wood floor or barely avoided a Darwin Award as we flew over the hood of a car that cut us off only because we had martial arts experience to instictively tuck and roll. Now I don't sit in the front of a boat knowing that the driver likes to go fast cause I don't need G force from a poorly padded seat to smack me like a trebuchet launching my derriere. Only it gets pulled away before the strike as a pinball gets it's tap into play. Anatomy is a good thing if you got control of everything that can hurt you and protect yourself accordingly.

This is a tremendously cool post, Pal!!

That's a head-scratcher. Aluminum or wood, bats weigh the same and have the same properties as far as physics (and trauma medicine) are concerned. They just break less.

While it's good to be more proactive in protection, it's hard to see the line when many of us grew up swinging from ropes strung from a rail in the loft of a barn over a wood floor or barely avoided a Darwin Award as we flew over the hood of a car that cut us off only because we had martial arts experience to instictively tuck and roll.

I suspect that Our Host will wince horribly when he reads this. Similar arguments ("Hey, I had the measles -- it's no big deal.") are used to belittle all sorts of lifesaving measures. The problem is that our personal experience is too narrow to be a useful guide to relatively rare events, such as pediatric auto fatalities.

I'm a big believer in Free Range Children myself -- but we need to face the facts as they are and use judgment, not our notoriously fallible human risk perception.

I'm pretty sure that argument wasn't intended (although on first glance i thought it was). One of my acquaintances takes that attitude ("it never killed us!"), but in fact it DID kill us.

About 3 years ago I fell in a restroom after slipping on some water, (banana peel style like in the cartoons) and hit the side of my head rather hard on the tile floor. I did not black out, just felt a bit shocked immediately, and did not notice any other symptoms there after. I never did notice any brain injury symptoms, and I have been well since.

However, in the last months I have been experiencing mild vertigo and light headiness, as well as a mild lack of concentration. This could be from paying too much attention to it, but I was wondering if brain injuries can result up to 3 years after the incident? If a slow developing problem could occur overtime following an injury?

For anyone with the time & interest in this subject...
You are invited to read my diary, it is of my wife's ordeal over a 12 month period.
The diary is located here:
http://forums.delphiforums.com/AspieAutiAdults/messages?msg=2171.25
you may have to register to view it but I assure you it will be well worth your effort.
I also must alert you to the fact that there are 26 entries & that you will have to look at the bottom of each page to continue the story.
Also be fore warned there is NOT a fairy tale ending.
I offer this up to you in order that you might place greater credence in protecting yourself and THOSE YOU LOVE as we all seem to think a calamity of this nature only happens to others.
As for myself, a single blow to the head from a baseball sized rock at 12 yrs. of age altered my life dramatically...I went from being a straight "A" student to being a total failure. I tried to regain my former self thru imitation of what I observed around me & coupled it with what I could recall of my former self & interests, my life became chaotic & out of control & I never received a proper diagnosis, treatment or rehabilitation. It was ONLY thru my wife's rehab that I came to recognize my own symptoms & failings & begin to deal with the actual problems. PLEASE...do NOT hesitate to get medical attention ASAP that involves an EXPERIENCED Neurologist, and in the event you or someone close to you suffers a head injury DO NOT EXPECT that the patient will EVER be exactly the same as before.

FYI: The Chicago Tribune has linked to this post!

Woah. Hm.... I around a decade ago violently tripped head-first into a solid concrete wall from a meter away or more, giving it a proper headbutt. I had a headache for an entire week afterwards, but didn't think of mentioning this to anyone. I wonder how much brain damage that incident gave me... I wonder if there would be any point in having someone take a look at my brain now... Bah. :-/

I had a friend who was a passenger in a car, riding without a seatbelt on, when they were in a very minor accident, the type of thing that would have not even left a bruise normally. Unfortunately the passenger door popped open and she fell out, hitting her head. Initially she seemed fine, but she was dead within hours.

My daughter participated in equestrian sports, jumping large horses over high fences. Helmets were mandatory, but the more-padded helmets were considered, um, aesthetically undesirable, as in "lame," "uncool," and so forth, by many of the teenagers. I insisted she wear the thicker helmet, even if she rolled her eyes at me and said she looked like a "mushroom head." Fortunately she has survived, but it's scary to think what could happen, even with a helmet.

We've been getting hits from some weird helmet-denialist board. As DC pointed out, helmets are not a "no-brainer" in the sense of the topic being complex. The overall effect of helmets is a good thing. There are subtleties to the topic however. Some types of injury are more effectively prevented by helmets than others, but studies have shown at least some effect on all types of head injuries (although the studies are necessarily case-control rather than RCT).

For example,
JAMA Vol. 276 No. 24, December 25, 1996
Accident Analysis & Prevention [ACCID. ANAL. PREV.]. Vol. 26, no. 3, pp. 325-337. 1994.
Pediatrics 1994;93;567-569

In many studies, these reductions in injury applied to all head injuries, not just penetrating trauma.

The fact that helmet use doesn't protect against severe blunt trauma injuries as much as it does against penetrating trauma does not mean we shouldn't use them---don't fall for the fallacy of impossible expectations. I think, based on the data, that DC's statement that helmets do not protect against severe head injuries AT ALL is a bit hyperbolic, but still his general points were very useful.

This is a great read! I sorta wish this info was available for a more objective article when a few weeks ago (and currently as they move slow) somebody was trying to get aluminum bats banned from little league ball in Chicago using statistics that were pulled out of an unknown place resulting in an alderman doing the same almost. While it's good to be more proactive in protection, it's hard to see where to draw the line. Some of us grew up swinging from ropes strung from a rail in the loft of a barn over a wood floor. As I was riding a bicycle in a hurry to catch a train I barely avoided a Darwin Award as I flew over the hood of a car that cut me off only because of experience to instictively tuck and roll. Now I don't sit in the front of a boat knowing that the driver likes to go fast cause I don't need G force from a poorly padded seat to smack me like a trebuchet launching a pinball into play. I consider risk and what's acceptable for me. If you got control of everything that can hurt you and protect yourself accordingly, anatomy lessons are something an old person gets the hard way. Yet statistics tell us control is an illusion while we legislate saftey for the virgins.

PalMD, there's literature on helmets, yes, but is there good science? Your JAMA and Pediatrics references are from Thompson, Rivara and Thompson, who are the sort of amateurs who give case-control studies an undeservedly bad rep (helmets make you more likely to be white, and to have health insurance), and the Accident Anal&Prev article looks at the period after helmet legislation in Victoria, Australia, and attributes all change in HI numbers to the effect of helmets, while failing to note that there was a decline in cycling and a simultaneous decrease in pedestrian casualties.

Other research suggests that with the concomitant decline in cycling the risk per cyclist increased.

On the whole, what I know of the research on bike helmets suggests that DC Sessions is entirely correct -- reduced death rates do not appear with large increases in helmet wearing, while there may be some effect on less serious injuries, evidenced in presentation at A&E.

What is possibly a better paper than TRT is Maimaris et al, BMJ 1994;308:1537-1540 (11 June). It involved pretty careful tracking of cyclists attending Addenbrooks Hospital in Cambridge, over a reasonably long period, and the OR for an effect of helmets on head injury was significant. However, that finding was entirely due to the fact that no helmet wearing children presented with head injury, and there was no significant effect for adults. Their problem was that, even in a big A&E dept like Addenbrooks, HI (of cyclists) is a fairly rare event, and they simply didn't have enough data -- over 6 months, about 1,000 cyclists showed up, about 10% with HI. Not enough for robust findings. And even with that we have the usual problems with confounders (people who choose to wear helmets and choose to attend A&E have, maybe, lower rates of HI -- how much is due to helmet wearing and how much to other characteristics?).

It is just hard to get good science done on this issue. And as DC Sessions made clear, the physics is against any significant effect in high speed impacts.

And as DC Sessions made clear, the physics is against any significant effect in high speed impacts.

More like, "low-speed impacts," assuming that we're comparing those with equal energy. I hope it's obvious that if a cannonball hits your head at Mach 0.7 it really won't matter whether you have a helmet on or not.

IOW, all of the studies, including the one you cited, showed a reduction in serious injury (with correlation, and PROBABLE causation) with helmet use, and like any other denialist, you put your fingers in your ears and go LALALALALA

I will not allow comments that encourage unsafe behavior.

As dc said...some impacts are not survivable...

Cannonballs don't worry me, and I don't often reach Mach 0.7, but isn't hitting a truck (or a tree) at 50-60 km/h a high speed impact?

People, we now have a specific statement on the Natasha Richardson case from someone who is, no way around it, an expert:

http://www.ski-injury.com/latest_news/nr

Dr Mike Langran is not only a ski patroller but Director of the Scottish Snow Sports Safety Study, UK secretary of SITEMSH (International Society for Skiing Traumatology and Winter Sports Medicine) as well as both Board member and UK National Secretary of the International Society for Skiing Safety (ISSS).

Also of great value:
http://www.ski-injury.com/specific-injuries/head

Read. Learn. Mike is good people.

IOW, all of the studies, including the one you cited, showed a reduction in serious injury (with correlation, and PROBABLE causation) with helmet use, and like any other denialist, you put your fingers in your ears and go LALALALALA

I will not allow comments that encourage unsafe behavior.

I find that response insulting, and frankly juvenile. I won't be back.

Cannonballs don't worry me, and I don't often reach Mach 0.7, but isn't hitting a truck (or a tree) at 50-60 km/h a high speed impact?

It is, and a direct impact with a tree at that speed is, basically, not survivable. On the other hand, getting your head whacked by a branch tip at that speed is more survivable with a helmet.

Note that running into a tree at 50 kph is going to do you in even if by some miracle your head is completely undamaged; it will, among other things, rip your heart loose from its supports and tear your aorta -- which will save you from bleeding out from the massive fractures, punctured lungs, ruptured solid organs, loss of respiration consequent to high cervical spine damage, etc.

And, yes, I'm speaking from experience.

High-speed low-mass collisions are aided by helmets. Low-speed high-mass collisions have the same energy but are helped much less. High-speed high-mass collisions (the cannonball) simply aren't survivable, period.

This is a great read! I sorta wish this info was available for a more objective article when a few weeks ago (and currently as they move slow) somebody was trying to get aluminum bats banned from little league ball in Chicago using statistics that were pulled out of an unknown place resulting in an alderman doing the same almost. While it's good to be more proactive in protection, it's hard to see where to draw the line. Some of us grew up swinging from ropes strung from a rail in the loft of a barn over a wood floor. As I was riding a bicycle in a hurry to catch a train I barely avoided a Darwin Award as I flew over the hood of a car that cut me off only because of experience to instictively tuck and roll. Now I don't sit in the front of a boat knowing that the driver likes to go fast cause I don't need G force from a poorly padded seat to smack me like a trebuchet launching a pinball into play. I consider risk and what's acceptable for me. If you got control of everything that can hurt you and protect yourself accordingly, anatomy lessons are something an old person gets the hard way. Yet statistics tell us control is an illusion while we legislate saftey for the virgins.

This is a tremendously cool post, Pal!!

Isis, admit it: you're just jealous that your ski trip didn't give you material this awesome to blog about.

And, no, much as I wish you well I will not offer any hopes for "better luck" next time! (For all I know you might come visit my mountain and, as we say, "Boring is good.")

So the temple is the weak spot? So there was a point to having an anapsid skull after all?

<sigh>

So the temple is the weak spot?

More like, "that honking huge hunk of gray matter is off balance."

Side-impact deceleration trauma tends to cause the brain to pivot around the base, with the side opposite the impact being stretched in the turn. This can tear an artery, which bleeds, fills the skull, and puts pressure on the brain.

There's no indication of any penetrating injury, temporal or otherwise.

A small percentage of the time the bleed can be venous, with a possible longer period of lucency. Also there are neuronal shear injuries...lots of nasty things can happen up there..

A small percentage of the time the bleed can be venous, with a possible longer period of lucency.

I would have thought that the low pressure of a venous bleed would be pretty self-limiting.

Have you ever noticed that engineers and medics have this almost reflexive fascination with failure modes? There's just something irresistable about them, no matter what is coming undone. It's so freaking easy to get caught up in the "what" and lose sight of the "who."

Phil,
I got my figure from our Australian state cycling organisation. The best study I can find from their links is

http://www.infrastructure.gov.au/roads/safety/publications/2000/Bic_Cra… CR 195: Bicycle helmets and Injury Prevention: A Formal Review (2000) This is a metaanalysis and has a good reference list.

The results are based on studies conducted in Australia, the USA, Canada and the United Kingdom, published in the epidemiological and public health literature in the period 1987- 1998. The summary odds ratio estimate for efficacy is 0.40 (95% confidence interval 0.29, 0.55) for head injury, 0.42 (0.26, 0.67) for brain injury, 0.53 (0.39, 0.73) for facial injury and 0.27 (0.10, 0.71) for fatal injury. This indicates a statistically significant protective effect of helmets.

When I was a freshman in college I got a call from my mother that my brother was in the hospital. Using all the bravado one has as a 24 year old mountain climber, he and a friend decided to practice repelling down the side of their apartment building.

The anchor they put on the roof failed and he fell several feet hitting his head on concrete. His friend immediately drove him to the hospital, where there was no question of an injury since he was spouting blood out of his ear. Which is why he is still alive, since it did not create pressure on his brain.

He spent multiple months in the hospital (I forgot how many, this was over thirty years ago). According to my mother he first seemed like a little kid, and then slowly came back to his own middle-twenties self.

A few years later he had another fall while climbing (D.C. Sessions, you might be familiar with the area: Coronado National Forest, near Sierra Vista). But it was a softer landing on a ledge.

He stopped climbing after his first child was born, imagine that. He has found other safer hobbies (oh, like camping, traveling, dealing with lots of family videos, and most recently bouncing his first grandchild on his lap.)

I feel so much for Ms. Richardson's children, who are just a bit younger than my youngest. What a horrible accident.

This useful discussion makes me realize just how poorly we are all educated about these issues in public schools. I went through 4+ years of (U.S.) health class and I do not recall any information on blunt head trauma--just lots of awkward descriptions of fallopian tubes and how a wineglass, beer mug, and shot glass all "packed the same punch". What my teen self instead saw on the head injury front were action films, pro wrestling, and other "evidence" that things like headbutts or slams into hard surfaces were to be considered easily recovered from, humorous, or "awesome".

At 16 or 17, I jumped off a chairlift to fetch a ski I'd dropped, falling about 15+ feet into soft snow, but I still recall the surprising feeling of my head and upper body being accelerated down with overwhelming force into the snow. Luckily I was fine, but I would never have imagined then that such an event might--had the snow not been as soft--result in death.

This conversation (and others like it) are very valuable. Thank you all.

Thanks for the link David: I'll follow it up at some point.

Speaking personally, I fear the benefits of helmets may be overstated in the general population to the point that they enable more risk-taking behaviour: My brother once turned to me unprompted during a discussion on ski-ing in general and said "I love helmets, they make you invincible". Obviously to a certain extent this was deliberate hyperbole, yet clearly if one has an unjustified level of faith that "a helmet will save them" it seems to me more likely that they're going to end up in the ER with an injury that the helmet didn't save them from.

It's the curse of protective equipment advocacy: if you tell the truth about the benefits (that they're probably real, but very limited) then people are less likely to wear them, but if you push them hard, then people may gain an unjustified sense of safety from wearing them.

PalMD, have you thought of a post on concussions? It would be a useful piece of education - you have 3 or 4 commentors here who have questions and would like information (for example, there's no evidence for late neurological consequences, but people often mistake ordinary difficulties for symptoms of brain injury).

The 'risk homeostasis' aspect of helmets is probably oversold. What's the good evidence (not just time series, but same-time comparison across states/cities, etc) that give information on this? There's good evidence that motorcycle helmets save lives, and the push to repeal mandatory helmets has increased the number of organs for donation. For example, here's a good controlled study; http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6F-4T55V80-…

At 16 or 17, I jumped off a chairlift to fetch a ski I'd dropped, falling about 15+ feet into soft snow, but I still recall the surprising feeling of my head and upper body being accelerated down with overwhelming force into the snow. Luckily I was fine, but I would never have imagined then that such an event might--had the snow not been as soft--result in death.

And not just yours -- jumping from a lift can derail the lift and dump out others who are not prepared and may be much higher up over (for instance) rocks.

If there is one behavior at ski areas that I hate most, it's lift jumping. Were it up to me, every one we catch would be charged with reckless endangerment and, pending trial, spend a few nights in Whiteriver jail.

D.C. Sessions wrote:
"The statistics are that helmets do a very good job of reducing minor head injuries. You would not believe the self-inflicted wounds I see with snowboarders, including lacerations to the crowns of their own heads from their boards' edges. I kid you not. Helmets are wonderful for those, and frankly they're also much better at keeping your head warm in variable weather. I love them.

However, those same statistics tell us that helmets don't reduce severe head injuries at all. That's just the way it is."

To the contrary, ski helmets DO reduce the severity of head injuries and DO reduce the risk of fatalities, as shown by several well-designed and peer-reviewed studies in the past several years. My colleague Stewart Levy, MD, a neurosurgeon, and I (a neuropsychologist and brain injury rehabilitation specialist) have been performing helmet counts at Colorado ski areas since 1998, and tracking admissions to our Level I trauma center to assess the effectiveness of helmets (and publishing the results! And trying to educate ski patrolers!). We have looked at over 800 patients admitted from the slopes. Even with major mechanism injuries (i.e., falls greater than 10 ft.), helmets reduced the severity of the brain injury, as shown by lower brain injury severity scores, fewer positive CT scans, and fewer skull fractures and intracranial hemorrhages. For instance, in one series of helmeted snowboarders admitted for a brain injury, only one of 19 had a positive CT showing a small contusion, and he had fallen after a 15 ft high jump and landed on his head wearing an uncertified helmet. Another guy fell 40 ft. off a cliff, cracked his helmet in half, sustained rib fractures, thoracic spine fractures, pelvic fractures, facial fractures, etc., and still had negative CT and MRI of the brain. He was given a dx of brain injury based on his two days of disorientation. None of the helmeted boarders had skull fractures, compared to 15% of the unhelmeted. Almost all helmeted skiers we have seen are discharged with a dx of "simple concussion" whereas 35% of unhelmeted brain injured skiers are discharged with a more serious diagnosis.
The data also clearly indicate that it takes a bigger fall to get a brain injury if you are helmeted than if you are not. That is, 32% of helmeted brain injuries are from "major falls" (>10ft.), compared to only 5% in the unhelmeted.
Comparing the rate of helmet use on the slopes (currently approximately 45% at 8 ski areas in Colorado) with the admission data, consistently shows that helmets reduce the risk of brain injury by about 75% and reduces the risk of fatality by 80%. We have also seen no correlation between helmet use and other injuries, including spinal injuries. There is no evidence to support the myth that helmets promote risk taking behavior or lead to delusions of "invulnerability." That's like saying that ABS brakes lead to faster and more reckless driving!
Take-home lesson: always ski with a helmet!
George Rossie, Ph.D.

I admit that I don't have studies regarding helmet use, just the anecdotal evidence of every cyclist I've ever known (and I grew up in a cycling family) telling me a "my helmet saved my life" story. Now, that's a hobby where most of the time it's a skidding injury, so helmets seem like a really good idea. And really, you slide into a curb, you're more likely to catch it in the back/side than in your head unless it's a really spectacular fall.

But I have to wonder, having gone over-handlebars twice, once (foolishly) without a helmet and once with: has anyone studied whether there's a difference in how we fall when wearing a helmet vs when not? I would think that people would be more likely to properly tuck and roll when wearing one, and would try to catch oneself (breaking wrists or collarbones in the process) when not. But I'm not a scientist, and don't have the foggiest idea how to even search to see if something like that has been studied.

Thanks, George!

George: "That's like saying that ABS brakes lead to faster and more reckless driving!"

Ironically some of the strongest evidence for risk compensatory behaviour comes from studies of drivers and ABS systems.

This doesn't mean that one can blindly read across from ABS systems to helmets of course, but you couldn't have chosen a worse example to scoff at!

George: "That's like saying that ABS brakes lead to faster and more reckless driving!"

Ironically some of the strongest evidence for risk compensatory behaviour comes from studies of drivers and ABS systems.

In my part of the mountain West, it's widely known that trees attract 4WD vehicles. When there's ice on the road, it's almost always the 4WD jobs that skid out.

"Ironically some of the strongest evidence for risk compensatory behaviour comes from studies of drivers and ABS systems."

Point taken. Maybe I should have said "That's like saying that wearing a seatbelt leads to more reckless driving." That one work better??

Yesterday I had to give an hour long talk to a national audience. It was stressful, because a couple days prior, my laptop hard drive failed. I had to go to BestBuy for a new 'puter. Then I couldn't find an MS Office install disk, so I couldn't open up my PowerPoint. I had to email it to someone to save it in an earlier version of PP. Then I had to tunnel to a Terminal Server to open it. Gack!

Then they changed the room I was supposed to be at. I told 'em about needing to get to a Terminal Server to see my slides. So last minute race around for a LAN cable.

Does this stuff happen to other people, or am I cursed?

The talk went fine. When I got home I could hardly stay awake. I went to bed at 7:00; normally I get to bed around midnight. Woke up this morning with a headache and felt wiped out. Got nothing done today.

Makes me wonder if I made my post-concussive brain work too hard.

My husband thinks I'm like my normal self. I'm not entirely sure. My sense of balance still seems a little off. And I'm still not getting work done as I should.

I had to go to BestBuy for a new 'puter. Then I couldn't find an MS Office install disk, so I couldn't open up my PowerPoint.

I can't help you with the brain fog, but you can always score OpenOffice.org -- no disk to find, and always downloadable.

Works for me.

Be well,
--
D. C. Sessions

Interesting! I share Magatha's question; is the epidural hematoma pictured prove fatal more often then not? How is that sort of thing fixed?

Anyway, I'm also going to be more careful about helmet usage in the future. I ride my bike to school, which isn't a long trip, so I'm usually lazy about taking a helmet.

I absolutely love reading posts like this - it gets me excited for post-high-school education. =)

D. C. Sessions: Thanks for your comments and perspective!

George: Yes, I agree that seat belts are probably better, if for no other reason than the fact that they only come into effect during a crash, so the driver can't really learn how effective they are (surely only a madman would want to keep crashing to test their seat belt's effectiveness?). Air bags would be the other obvious vehicular equivalent. (Perhaps the wearing of crash helmets in cars ought to be the real equivalent though? I believe the head injury rates for car driving are considerably higher than those for skiing, although I don't have figures to hand.)

Returning back to the original topic, http://www.ski-injury.com/ contains the thoughts of another medical professional who is closely involved with skiing, both as a practitioner and from a professional POV, on the topic of safety in snow sports in general: Worth a read I think.

Returning back to the original topic, http://www.ski-injury.com/ contains the thoughts of another medical professional who is closely involved with skiing, both as a practitioner and from a professional POV, on the topic of safety in snow sports in general: Worth a read I think.

Including citations to published work on helmets and head injuries that contradict Dr. Rossi's [1] results, with some comments on methodological issues that may or may not apply.

Since the cites are all paywalled, this engineering physicist is stepping back to let the people who actually have data do what science does.

[1] In this context, it's a tossup whether the honorific is appropriate under the general rules; the PhD is certainly relevant even though the topic is medical. If I err, it is in the direction of earned respect.

Confidence influences are interesting - Antilock Brakes had poor statistical results early on that have improved with wider take up. Generally,

some of those who willingly take risks will take up safety equipment. If everyone is expected to wear helmets, some of those not wearing them

will be risk takers in other ways too.

Studying cyclists who have been injured and treated at a hospital seems to be a fair way to get a semi-controlled population - non head/neck

injuries are not influenced by hemlets, and researchers can then compare the sample to the general population to check for bias. Those with head

injuries are the study group and those with non-head injuries become the control groupp. That is what a series of studies has done, e.g.

Author Thompson, D.C., Rivara, F.P., Thompson, R.S.
Title Effectiveness of bicycle safety helmets in preventing head injuries. A case control study
Journal Journal of the American Medical Association 1996
Design Prospective case control study
Outcome Head injury, Brain injury, Severe brain injury (Intracranial injury or haemorrhage)
Subjects 757 cases = bicyclists with head injuries (treated or admitted or died) 1992-94
2633 controls = bicyclists treated for non head injury 1992-1994
Helmet use 29% of cases wore helmets ; 57% of controls wore helmets ; 51% overall wore helmets
Helmet type 49% hard shell ; 29% thin shell ; 19% no shell/foam
Results

DC Sessions Thank you!

I'm typing this one handed because, the one day I go wrist brace-less, I take the brunt of a snowboarding fall on my left wrist hand. Season ender for sure (glad it's March not Dec). Managed to keep the helmeted head from hitting the slope sothat's a silver lining.

No system is perfect, but you can do what you can to move the odds in your favor.

My 17 month old daughter hit the back of her head in the middle near the thing that raises up. She has a small knot but its pretty raised up. She is completley normal but I am worried because of where she hit it. I dunno should I be worried?

We don't answer specific medical questions here. I encourage you to seek medical attention.

Dear PalMD:

I appreciate your blog- it is very interesting, as I am an english rider who frequently falls off the horse here and there and have bumped my head in a Charles Owen helmet several times. The first was almost 2 yrs ago, when I blacked out unconscious and woke up seconds later in utter disbelief that I was even at the barn!-- (as I lay'd face down in the sanded arena). I was fine after that fall- just bewildered by the 'blacking out'. Since then, I've noticed as hard as I try to be defensive and proactive in falling safely, I tend to bump the back of my head (only 3 times since the big fall) after I've landed on my backside usually. IS THERE ANY SUCH THING AS BUMPING YOUR HEAD ONE TOO MANY TIMES- EVEN THE SMALL BUMPS? I tend to have a headache and my MD says that since Ive gotten through the first 24 hrs, I should be fine.. whenever I worry after a fall. I take a dose of tylenol and that's that. I am investing in the best helmet one can buy for equestrians... Im not taking anymore chances. Thanks you for giving me some good advice if you can.

@tami
http://www.neurosurgerytoday.org/what/patient_e/sports.asp

I just went to the ER to have my head checked out. Prior to this (about 3 weeks ago), I had seen my GP at an appointment, two days before, I had slipped and fallen, he checked my eyes, and said 2nd Degree Concussion. I was stunned. He explained 10-12 days of headaches, symptoms, etc. He was an enormous help.

Going to the ER, after an icicle hit me in my hairline, just above the temple, and after a sledding incident, the only thing checked were my reflexes. The doctor there was dismissive, and it begs one to wonder, if there should be a diagnostic sheet they should go through when assessing a head injury. I felt I could have asked my daughter to use a spoon from home to do these diagnostics, he did not even check my eyes! Meanwhile, I feel woozy, nauseated, and "out of it", trying to grasp for my words. Maybe he thought I was a drug seeker, who knows. Yes, the ER was busy, I told him I didn't want to waste his time (without sarcasm), as there were more emergent individuals than I, with coughs and colds. I think I took more of a risk going to the ER, as I was coughed on by a senior citizen.

Keep an eye peeled for "The Checklist Manifesto" by Atul Gawande". I'm probably going to review it soon and it goes to your comment.

I have been in two different wrecks both times i hit my head. I fell down and hit my head about nine months ago. A day later i started seeing lines in my eyes then i felt as if i wasnt in my own body. Then i got really dizzy. Then i couldnt see anything it all went black. This would last about 30 mins . Its been happening eversince i hit my head at least once a month .I have been to the doctor and they say its not my eyes. They say its migrains i dont beleive them. My whole life i never had this happen to me. Why would i be doing this?

The image of the epidural hematoma has vanished.

I still see it...

Vanessa -- see a doctor. If you don't like what the last one said, see a different one. I'm no doctor myself, but what you describe sounds very frightening. I know I'd be worried.

It's fun to see this old thread again. Well, not fun in the sense that it's about bad things happening to the brain, but as noted earlier in the comments, engineers and medics (I'm the former) do have a fascination with failure modes....

I am reminded of the time I was skiing as a teenager and got plowed over by a reckless skier from behind. It's the only time I've ever blacked out due to impact. (I fainted once due to dehydration and anemia, and I've been under anesthesia a few times. But those aren't the same.) I remember my dad (a doctor) being very worried.

My uncle used to be a MAJOR snow-hound until his body wouldn't let him anymore. (A number of problems, but the first one was when a big construction vehicle came down on his arm, crushing it.) He and his best buddy would go skiing together regularly. In the late 80s or thereabouts, they were out skiing once at Bridger Bowl, and the weather turned sour. They figured they'd finish their run and then call it a day. It was very windy, and the exposed areas were becoming dangerously icy. With blowing snow, visibility was also limited, and my uncle's friend inadvertently strayed onto a different run than the one he'd intended. It was a black diamond, and one which he'd skied before, but never in conditions as poor as this. He had no traction whatsoever; his edges couldn't catch anything and he wiped out. The tree that he hit probably actually saved his life -- it was only a short way down the slope, and so he hadn't picked up very much speed before hitting it. His head was fine, thank goodness, but he ruptured his pancreas and broke a lot of bones. They did manage to save the pancreas, and he eventually made a full recovery. But what a difference just a few feet can make.... If he'd wiped out just a few feet earlier, he wouldn't have gone down the steep, icy slope. If he'd slid a few feet to one side, he'd have hit his head. If he'd slid a few feet to the other side, he'd have gone right on down, accelerating until reaching the really bad stuff at the bottom (more trees, some rocks, and big steel ski lift supports). He probably would've died. It took three hours just to get him off the slope, and more time for the ambulance to make it all the way around the mountain range to pick him up.

I can't get the image (the 2nd scan) to show up either, just comes up as the dreaded red x no matter how many times I ask it to load.

My boyfriend was swinging round on an a metal bar when he fell off at a height of about 8 foot, he hit the back of his head hard. There was an immediate concussion,then his eyes were rolled back in his head, when he slowly came round his speech was slurred and he could not say what he wanted to. It was terrifying. A day later and he has continuous headaches at the opposite end of the head and says he's not thinking straight. Could this be serious? Is there anything I can do, should i use ice on the bump?

Mary--

Get him medical care at once. Call the emergency number (911, 999, whatever it is where you are), or take him to the emergency room or clinic yourself. Now.

I fell on my head after being pushed by a 100 poung dog. My head swelled right away. I applied ice to reduce the swelling. It's now a week later and my bump has gotten smaller, but it's still painful and it itches a bit. I don't have any symptoms other than the pain and bump that is still evident a week later. Should I go to the doctor?