The role of the reticular formation in the coma of head injury.

H EAD injury has been a major problem of man for centuries. The first written account of the treatment of such appeared in the Edwin Smith Papyrus around the 17th century, B. C. Thirty-four centuries later in 1883, Jean Louis Petit was the first to recognize cerebral concussion as a separate entity and distinct from brain compression by hemorrhage. Cerebral concussion was first defined by Benjamin Bell in 1873 when he said, "Every affection of the head attended with stupefaction, when it appears as the immediate consequence of external violence, and when no mark of injury is discovered, is in general supposed to proceed from commotion or concussion of the brain, by which is meant such a derangement of this organ as obstructs its natural and useful functions, without producing such obvious effects on it as to render it capable of having its real nature ascertained by dissection." Little actual refinement in this definition of cerebral concussion has occurred in the subsequent 80 years. 1~ The physiologic basis for the clinical phenomenon of cerebral concussion is not completely understood even though closed head injury is an increasingly common occurrence. The mechanics of brain trauma were thoroughly studied by DennyBrown and Russell 3'4'5 who established the laboratory criteria for concussion and made a distinction between acceleration and compression concussion. Holbourn, 12 studying the physical forces involved in head injury, showed that the rotational rather than linear acceleration forces are the main cause of brain damage in head injury, these forces being responsible for "contrecoup" damage, hemorrhage, and "probably" concussion. Gurdjian et al. 1~ analyzed physical factors in concussion and demonstrated that acceleration, deceleration and compression all result in measurable elevation of the intracranial pressure. They concluded that sudden increase in intracranial pressure caused concussion and that the shorter the time duration of the increased intracranial pressure, the higher the pressure necessary to cause a concussive effect. Investigations of the physiological basis of head injury have proceeded slowly along two lines--the measurement of biochemical changes and meas-