Brain death criteria in the United States includes: (1) no wakefulness or movements other than spinal reflexes for a 48-hour observation period; (2) neurological examinations at the beginning and at the end of the observation period showing no clinical evidence of brain or brainstem functions; and (3) either no electroencephalographic cortical activity at the time of the neurological examination or no cerebral blood flow within the observation period (Figure 64.1).

Figure 64.1.— Cerebral blood flow study demonstrating absence of cerebral blood flow.

DIFFERENTIATING COMA FROM STATUS EPILEPTICUS

Partial and generalized electroencephalographic status epilepticus may be associated with a state of altered mental status clinically similar to coma. The distinction is based on EEG findings. The distinction between status epilepticus and coma is important because status epilepticus is a hyperexcitable neuronal state that requires treatment with antiepileptic drugs, whereas coma is a hypoexcitable neuronal state that does not require antiepileptic treatment.