1981 Volume 21 Issue 11 Pages 1147-1152
Far field acoustic responses (FARs) were recorded at the vertex in 104 cases suffering from severe head injury. Alterations in the responses were compared with Glasgow coma scale scores, CT findings and outcome. In 30 cases, FARs elicited by bilateral monoaural stimulations and binaural stimulations were recorded for evaluation of the asymmetrical abnormalities. These results may be summarized as follows:
Two different types of alterations in the responses were recognized in the acute stage of severe head injury. These two types were (i) prolonged latency or disappearance of the 5th waves and (ii) disappearance of the 1st to 5th waves. The former type is suggesting damage to the midbrain improved within two weeks after the trauma. In contrast, the latter type indicates the dysfunction of the pons and medulla remained. These alterations in the responses were correlated with the outcome three months after the trauma. In 73% of 22 cases whose severity were less than seven on the Glasgow coma scale, abnormalities of FARs indicating the dysfunction of the brain stem were shown. Asymmetrical abnormalities of 5th waves were found in 30% of 30 cases suffering from severe head injury. However, this lateralization of the upper brain stem lesions by FARs were not significant for predicting the outcome three months after the trauma.
Based on these results, it was concluded that the FAR is a useful indicator and predictor concerning the function of the brain stem in patients with severe head injury.
