Traumatic lesions of pontomedullary junction.

An autopsied series of 162 consecutive fatal head injuries was analyzed for location and type of primary brain stem injury. Of 41 cases with primary brain stem injury, 24 (59%) demonstrated 22 tears and 2 complete transections at the level of the pontomedullary junction. Three cases are presented in detail to illustrate the range of structural and functional damage seen with trauma at this level of the brain stem. A pathologically verified case of traumatic "locked-in" syndrome is reported, including serial brain stem auditory evoked responses that are correlated with the neuropathological findings. In addition, two cases of primary traumatic damage at the pontomedullary junction (one tear and one total transection) are described; these were associated with instantaneous death at the time of injury. Pathophysiologically, the tearing or disruption occurring at this level results from rapid hyperextension, which produces stretching at the pontomedullary junction.