Question:
These phrases ring true for 70% of head injury victims whose injuries may be described as minor but whose sequelae prove not to be. In fact, we are recognizing that this is a health problem of considerable magnitude.

The numbers are large: almost one million individuals per year by conservative estimate excluding countless others who do not seek medical attention for what is perceived by both victims and caregivers to be a negligible injury. Studies show that between 1/3 to 1/2 of victims who were previously employed persons are still unable to return to work six weeks later. They are a group with high utilization of follow-up medical care in the months following the injury. So although the impact on each individual may not be as impressive as it is for more severely injured patients, the aggregate of life disruption and lost productivity is nonetheless inestimably costly to the individual, his family and his community. If minor head injury is not minor, then what is it?

Answer: The diagnosis of mild head injury is recently emerging as a distinct clinical entity with its own unique problems to patient and caregiver alike. It is defined as trauma in which the head is struck or moves violently within the skull, and results in a transient alteration of consciousness. The trauma may be the result of a fall, a blow to the head or a whiplash injury.

Operationally the diagnosis is best characterized by the things that are not present rather than the things that are -- what might be called the "litany of NO" - brief or NO loss of consciousness, NO neurological exam abnormalities, NO CT scan abnormalities, NO expectation of sequelae, NO follow-up, NO rehabilitation and unfortunately NO preparation for residual deficits. Despite apparently normal test results, many patients with mild head injury experience an array of symptoms spanning physical, cognitive and psychological functioning.

Acutally the whole process is quite a bit more complicated then was presented. Take a look at a good textbook on Pathology (or better yet neuropath or neurosurgery) if you want a good explaination. BUT.....

The dilation of pupils is actually a middle event typically caused by the beginning of a type of upper brain herniation (an uncal herniation, if you really want to know) placing preasure on cranial nerve 3. Initially, this impingement will knock out the parasympathetic fibers leading to overwelming sympathetic tone and pupillary dilation. Later as the pressure increases and CN III is further damaged, the motor fibers will be affected resulting in a deviation of the eye 'down and out' on the side of the injury.

Eventually, if this increased pressure is allowed to progress, you will begin to herniate the brain stem. This will result in damage to the vasculature in the area, leading to small areas of hemorrhage (called Duret hemorrhages) in the brainstem. At this point coma and death will occur within a short period of time. This also explains why after some episodes of severe edema even if you manage to get the ICP and cerebral edema down the patient will often become locked into a persistant vegitative state. There is an area in the midbrain called the reticular activating system (RAS) which controls, for lack of a better word, 'wakefullness'. If this area is damaged (either by Duret hemorrhage or hypoxia), it becomes impossible for the patient to wake up and become alert.