Diagnostic and prognostic value of auditory nerve brainstem evoked responses in comatose children

The efficacy of auditory nerve brainstem evoked response (ABR) in the diagnosis and localization of brainstem lesions and its prognostic value in determining outcome were examined in 30 deeply comatose children. The ABR recordings obtained from each patient were correlated with the clinical, ancillary examinations and final outcome of these children. Clinical and ancillary examinations indicated damage to the cerebrum alone in 14 patients. In these children, ABR was found to be within normal limits. Isolated brainstem lesion was suggested by these examinations in 4 patients and their ABR recording showed absence of one or more of the brainstem response wave components or a prolonged brainstem transmission time (BTT). In 12 patients, damage to both the cerebrum and brainstem was suspected by clinical and laboratory examinations. In 8 patients, partial absence of brainstem waves or prolonged BTT was found. In 4, there was complete absence of all brainstem waves. All patients, regardless of etiology or depth of coma, with normal ABR, survived. Conversely, all children with complete absence of brainstem response waves succumbed. The prognosis of patients with partial absence of brainstem waves or prolonged BTT was variable. Some survived while others remained in a vegetative state or died. Our study demonstrates the importance of ABR in the diagnosis and localization of brainstem lesions and its value as a prognosticator of outcome in deeply comatose children.