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The Anatomy of a Concussion

A strong enough impact, or even a lighter impact at just the right angle (like a dodgeball to the head, a hit against a soccer pole or a sail boom), can jostle the brain forcefully within the skull.
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A Perfect Day in the Bay

Nellie was out on the bay in a small sail boat with her two friends when WHAM! -- the boom of the sail swung out and struck her, jettisoning her into the water. She felt embarrassed more than hurt. The 12-year-old quickly clambered back onto the boat, her cheeks burning.

"I'm fine," she said to her concerned friends, "C'mon, let's go!"

The girls were racing four other boats on a hot summer Thursday afternoon. When the day was over and her parents picked her up from the marina, Nellie was bursting with excitement over their win. She forgot all about her accident, except every now and then, she unconsciously rubbed the back of her head where the boom made contact. It felt sore.

Nellie slept like a baby that night, utterly exhausted and wolfed down her breakfast the next morning, ravenous. Around lunch time, she began to develop a headache, slight at first, then picking up speed. Her mother gave her some Tylenol and told her to drink plenty of water, suspecting that Nellie had been out too long in the hot sun the day before. She also seemed very irritable, which was unusual for Nellie.

By that evening, Nellie's head was throbbing so much that she skipped dinner and went to bed instead. By Saturday morning, her headache was no better and her parents became concerned. Nellie, ever the tomboy, was not one to complain about pain, and certainly not one to skip meals.

"I don't understand this," her mother said. "You have been out in the bay on hotter days before. It must be all the excitement of the race."

It was then that Nellie remembered about the boom. She told her incredulous parents.

"How," her mother exclaimed, "do you just forget to tell us something like this?!"

They rushed her to the local ER, where the doctor examined her and diagnosed Nellie with a concussion.

What is a concussion?

The brain, with the consistency and texture of uncooked liver or firm gelatin, floats in a bath of cerebrospinal fluid, suspended there by strong membranes anchoring it to our very thick skulls. We are all truly hard headed, even when we are amiable!

COOL FACT: Your brain, which weighs just about 3.3 pounds in air, weighs only about 0.1 pounds when cushioned by this fluid!

In other words, Nellie's brain, and yours, is well-protected within our hard skull-helmets, tethered by strong and fibrous membranes and floating in the shock absorbing cushion of cerebrospinal fluid. However, a strong enough impact, or even a lighter impact at just the right angle (like a dodgeball to the head, a hit against a soccer pole or a sail boom), can jostle the brain forcefully within the skull.

"I thought you had to pass out to have a concussion?" Nellie's mother asked the doctor.

"No," the young ER doctor replied. "You can have a concussion even when you are completely aware and awake."

"And just passing out doesn't mean you have a more severe injury than someone who doesn't," she continued. "Although, usually this is true."

The ER doctor was right. There are approximately 1.3 million concussions per year in the US. Concussions cause brain injury in obvious and in subtle ways (1). As jarring as this process sounds, most of us who have the misfortune of a concussion may suffer from symptoms such as headache, dizziness and nausea which generally resolve in a few hours to a few days (1).

The Anatomy of a Concussion

Two things happened when Nellie's skull came into contact with the sailboat boom. One, her brain moved within the skull in a direction opposite to the force of the blow, causing some mostly microscopic damage. Two, her top heavy brain hemispheres twisted against the willowy stalk of her brain stem, creating a torque type injury. Because the brain stem houses the cells which keep us alert and spray up and out into the brain, like slender stalks of a giant bouquet, the twisting leads to loss of consciousness. Also, small and generally transient changes occur within some nerve cells, disrupting the normal functioning of those cells and the neural networks they are a part of.

This is why in boxing, the punch that reliably produces a total knock out is a powerful jab to the side of the jaw from below, the torque moving the brain relative to the brain, causing the opponent to pass out cold for the count. In Nellie's case, the angle of impact was such that there was little twisting and so she did not pass out. Thank goodness, because as you will recall, she was knocked into the bay.

So Nellie went home, her parents reassured that she did not have a problem requiring emergency intervention.

FACT: Teenage girls who play soccer and volleyball are twice as likely to suffer from concussions as teenage boys who play the same sports (2). However, the sports with the highest rates of concussion are American Football and Australian Rugby, two games that are exclusively male (2).

By Monday, with her headache slightly better, Nellie went off to school. But at midday, the school nurse telephoned her mother. Nellie was sobbing with pain from a severe headache. Her mother picked her up and took her home to rest.

On Tuesday, she stayed home all day, but when she tried to watch television, she felt sick. As the day wore on, Nellie found that whenever she got up or turned her head, she felt dizzy, "like I was off balance ... the walls moved a little." This feeling made her nauseous and her headache worse.

Nellie was continuing to have persistent symptoms after her head injury, the so-called Post Concussive Syndrome. In the next post, we will discuss some of the anatomy and the surprising treatment, particularly her headaches and dizziness, two of Nellie's big complaints.

NB: All identifying information has been changed to protect patient confidentiality.

Selected References:

2) Giza C, Kutcher J, Ashwal S et al. Summary of evidence-based guideline update: Evaluation and management of concussion in sports. Neurology. 2013;80(24):2250-7.

For more by Gayatri Devi, M.D., click here.

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