There is a long-standing belief that if a patient did not lose consciousness during a head injury, then no serious injury has occurred.
This is not the case. It is the brain stem that is responsible for consciousness. Therefore loss of consciousness implies possible shock or injury to the brainstem. However, lack of brainstem damage and failure to lose consciousness does not mean that there has been no damage elsewhere. Vivid proof of this lies in the story of Phineas Gage.
In 1848, Gage, a highly regarded foreman working on railroad construction, was tamping blasting powder into a hole. The powder sparked blowing the 14-pound, 3-foot 7-inch tamping rod under his cheekbone and out through the top of his head.
Eyewitness accounts differ as to whether Gage lost consciousness at all; some claimed he never did. Others thought that he might have been unconscious (or merely dazed) for several minutes. But all accounts agree that he was not only conscious, but sitting up in the wagon when he was carted off to a nearby hotel to wait for a doctor. Obviously he had suffered severe injury, not to the brain stem, but to the left temporal and frontal areas.
When the physical wounds had healed, Gage returned to work with his old company but soon lost his job. The formerly temperate and responsible young man had suffered a radical change in personality. A contemporary reported that:
Gage was fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was 'no longer Gage.
Gage spent the next 10 years at a series of odd jobs
(including a brief period with P. T. Barnum as a freak show
attraction). Friendless and alone, he died of a seizure in 1860.
Gage's case is widely considered to be the first medically
studied demonstration that damage to the frontal lobes could alter emotion,
personality, planning and decision making, and impact socially appropriate
behavior. His experience also shows that it is not necessary to
lose consciousness to suffer profound alteration in brain function.
Whether one loses consciousness or not, the
significance and the consequences of injury are often misunderstood
by many medical professionals, by the victims themselves, and by others who
don't understand the problem at all but assume that you really ought to be
better by now.
It is certainly
misunderstood in Hollywood where characters are constantly knocked
unconscious yet never suffer ill effects. In The Wedding Planner, the
hyper-organized Jennifer Lopez is nearly run down by a runaway
trash dumpster. A passing young doctor saves her by hurtling across the street
to push her out of the way, knocking her to the ground and smashing the back of
her head into the pavement. She awakens in his hospital where the
doctor announces that her X-rays and MRI "are clear" and therefore she
does not have a concussion. Yet notice that she has apparently been
unconscious for the entire time it took to do X-rays, MRI and
evaluations (and never mind the paperwork!). In the real world, this
character would probably find that she could not organize as she used to
do, she probably could not read or sleep well, nor continue working as a
wedding planner. She would certainly find that she had suffered a brain
injury.
Loss of consciousness is not necessarily the measure of
damage. A common brain injury without loss of consciousness, now suspect in
much of the cognitive decline traditionally attributed to aging, is hypertension.
Hypertension is defined as blood pressure of 140/90 or above. The first number is the systolic pressure (from Greek systol, contraction) a measure of the blood's force against artery walls when the heart contracts. The second number, diastolic pressure, is the pressure during relaxation of the heart when the walls of the chambers move apart (Greek, dia) and fill with blood. Although usually considered a disease of the elderly, hypertension can appear in the 20s and 30s especially in overweight individuals. What matters isn't the age but the numbers: a person is hypertensive if either number is too high.
Hypertension does its damage by weakening blood vessels to the point of rupture causing aneurysm, stroke, or heart attack, disability or death. Very high blood pressure may cause headaches and nosebleeds, but more subtle symptoms such as shortness of breath and cognitive decline are commonly overlooked or attributed to other factors.
Hypertension can reduce attention, learning, memory and decision-making skills through constant stress on the brain including small strokes. Brain changes appear on MRIs as lesions in the white matter of the brain. "White matter" is made up of axonal nerve fibers that link neurons together. Damage to these communicating structures impacts all brain function, but especially memory, logic, and the ability to function well in life -- conscious or not.