Elizabeth A. Reid, MD Concussion: Temporary Power Outage O


NE of the most dra- matic of medical con- ditions is the concus-


sion—the total and immediate paralysis of brain function that can follow trauma to the head. Typically, someone who has suf- fered a concussion loses both consciousness and all reflexive muscle activity for seconds to minutes. Individuals with a con- cussion also may stop breathing and their blood pressure and heart rate may decrease. While these effects on vital signs are usually brief and not noticeable, on rare occasions they may re- sult in immediate death. As con- sciousness returns to those who do not die from their injuries, the victims may seem confused. They may not recall the fall or the blow that caused the con- cussion, and depending on the seriousness of


the injury, they


may suffer a period of time dur- ing which they remember noth- ing new and ask repetitive ques- tions about what happened. They may also seem aggressive or behave out of character in some other way.


Normality may reassert itself quickly after a concussion, but sometimes several weeks of irri- tability, insomnia, mood change, headaches, and dizziness follow. In other cases, an initial period of normality, known as a lucid inter- val, may be followed by head- ache, confusion, and drowsiness,


T H E E L K S M A G A Z I N E


indicating more severe trauma to the brain itself and its surround- ing tissues.


Concussion of some degree occurs in almost all closed head injuries, which are defined as those head injuries in which there are no skull fractures or penetrat- ing injuries to the brain. Depend- ing on the trauma involved, symp- toms of concussions vary from mild to severe. But whether a concussion merely stuns an indi- vidual or puts him into a pro- longed coma, the mechanism of the initial paralysis of brain func- tion is always the same. Under- standing that mechanism makes it easier to understand the de- layed worsening and persistent symptoms that sometimes occur.


How Concussions Happen The brain has a gelatin-like consistency and is not firmly teth- ered to its surroundings except at the base of the skull. When the head suddenly stops after a blow, or slows down because of a fall, the brain keeps moving. Concussions result from that con- tinued movement of the brain within the skull. First the soft ce- rebral hemispheres slam into the hard skull in one direction, and then they rebound and hit the skull in the opposite direction. The temporal lobes, which are where memories form, are espe- cially vulnerable to damage from this kind of impact. The actual


paralysis of brain function, how- ever, results from the movement of the tiny brain stem, which emerges below the center of the two large cerebral hemispheres and connects the upper brain with the top of the spinal cord. As the heavy cerebral hemispheres move above, the brain stem bends, rotating first in one direc- tion and then in the other. Inside the midbrain—the top part of the brain stem—a group of cells called the reticular activating sys- tem reacts with shock and shuts down all communication between brain and body, producing the immediate, dramatic symptoms of concussion. Whether a concussion results in a momentary sense of being stunned, a coma lasting from days to weeks, or death, all of these outcomes are caused by the rotation of


the brain stem,


which stretches when the head speeds up and slows down. Stretching may shear nerve cell connections, damaging them and preventing cells from communi- cating with each other. Prolonged symptoms or death indicate that there is more widespread dam- age to the brain in the form of contusions (bruises), hemor- rhages, and extensive shearing of the connections between brain cells. When these types of dam- age occur, delayed swelling can aggravate symptoms, and care- ful observation of


victims by


knowledgeable people is ex- tremely important.


Complications


Delayed symptoms that may require emergency surgery or hy- pothermia treatment typically come from brain swelling, bleed- ing from small veins on the sur- face of the brain (subdural hem- orrhages), or bleeding between the skull and the tough fibrous lining around the brain called the dura mater


(epidural hemor-


rhages). In 2009, actress Natasha Richardson died following a lucid period after a relatively minor fall while skiing. In her case, the fall was apparently enough to stretch and tear a vein between the in- side of the skull and the dura mater. This led to blood accumu- lating between the skull and the dura mater. Epidural hemor- rhages like this are neurosurgi- cal emergencies because as blood accumulates,


it causes


more of the veins that bridge the space between the dura mater and skull to stretch and rupture. As more veins rupture, the hem- orrhage expands and com- presses the brain,


initially pro-


ducing headache and lethargy. Confusion ensues as more blood accumulates, and the brain is put under increasing pressure. Un- less the skull is opened to drain the hemorrhage, the brain stem is finally compressed and the pa- tient dies. (Continued on page 54)


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