[Auditory brain-stem responses in head injury and significance of the Vth wave].

Auditory brain-stem responses (BSR) were evaluated in 37 head injured patients with Glasgow Coma Scale (GCS) scores of less than 10, with particular reference to abnormal findings in the Vth wave. Within three days of injury BSR were recorded by monoaural stimulation with an acoustic intensity of 80 dB hearing level and thereafter repeated. The patients were divided into two groups, those exhibiting wave V and those without. The 9 patients with absence of wave V (4 patients presented with no wave, 4 patients with wave I or II, and 1 patient with wave I to IV) died within 4 days of injury. The disappearance of wave V and patient outcome reflected brainstem injury, which was confirmed by CT and neurological findings. Twenty-one of the 26 patients in whom wave V was recorded survived and the remaining 5 died 5 days or over after injury due to complications (2 meningitis, 1 sepsis, 1 diabetes insipidus, 1 asphyxia). Prolonged latency of wave V was not an effective indicator for localizing brainstem injury or supratentorial lesions, and was unrelated to outcome. Prolonged latency of wave V was observed 24 times in 8 patients. These patients also revealed prolonged latency of wave I (22 times, 92%), wave III (22 times, 92%), and interpeak latency of wave I to V (23 times, 96%). The changes in the latency of wave V reflected the changes in brainstem functioning. From these findings, it can be said that prolonged latency of wave V reflects deteriorated brainstem function as a whole, rather than the presence of midbrain lesions.