To clarify diagnostic significance of intracranial circulatory arrest monitored by TCD, its temporal relationship with loss of cerebral and/or brainstem function was evaluated in 66 cases of impending brain death. We introduced a continuous, multimodal neuromonitoring system of somatosensory evoked potentials (SEP) and compressed spectral arrays (CSA) for assessing cerebral function, brainstem auditory evoked potentials (BAEP) and SEP for evaluating brainstem function, and TCD for measuring supratentorial circulation.
Neurological brain function was preserved after supratentorial circulatory arrest in 44% of cases, and supratentorial circulation persisted in 21% after loss of all neurological brain functions. In relation to cerebral function: supratentorial circulation persisted after loss of SEP N20; loss of CSA activity significantly correlated with supratentorial circulatory arrest. In correlations with brainstem function: SEP P13/14 (58% cases) was more persistent than BAEP beyond wave II (42%) particularly regarding supratentorial lesions. Time interval to loss of cerebral function was shorter than to loss of brainstem function. These time intervals were shorter, mainly less than 24 hours, with complete signal loss than with persistent diastolic reverse or systolic flow.
Loss of brain functions after supratentorial circulatory arrest progress rostro-caudally and are nearly complete within 24 hours.
