Brain-stem lesions after head injury

A full description of brain-stem injuries should include their mechanisms and types of damage, distinguishing those which are primary and occur at the time of the injury, from those which are secondary and result from changes elsewhere in the brain or in other parts of the body; and the various lesions should be related to the clinical condition of the patients. Unfortunately, knowledge is insufficient to allow any ofthese objectives to be satisfactorily fulfilled. Morphological studies on human material are necessarily limited to fatal cases, and largely to examples of severe injury. Knowledge of brain-stem changes after relatively minor head injuries is fragmentary. It depends on the occasional case recovering or recovered from a non-fatal head injury and dying of some other cause coming into the hands of a pathologist sufficiently interested to study the brain-stem in detail. This paper consists primarily of an account of the morphological changes in the brain-stem in injured patients; mechanisms are not discussed and reference to other factors concerned is made only when this is essential. Many accounts of brain-stem injury have been restricted to descriptions of the haemorrhages which occur in rapidly fatal cases, and the lesions, often haemorrhagic, which result from increase of supratentorial mass. Important as these are, it cannot be too strongly emphasized that lesions of different kinds and origins occur in the brainstem after injury. The full spectrum of change can be appreciated only when cases surviving different periods of time are extensively examined using a variety of staining procedures. Severe lesions may be present though the brain-stem appears normal or nearly so to the naked eye. Primary haemorrhages are first described and then the secondary lesions from tentorial herniation which tend to differ in distribution and are often partly or largely ischaemic. Other less well recognized changes and their distribution are then described. Often they are the result of primary injury but are recognizable by present histological techniques only in those who survive hours or days. Finally, the changes which occur in the brain-stem of patients surviving in coma for long periods are briefly stated and related to the other findings.