- This article presents a systematic review of the prognostic factors in coma caused by hypoxia and anoxia, and traumatic head injury. In the case of anoxic coma, poor prognosis can be determined very accurately at the bedside by the lack of brainstem reflexes assessed at day three post-insult. Electroencephalogram (EEG) and evoked potentials (i.e., auditory and somatosensory) detect additional patients with poor prognosis. Clinical examination is not as helpful in the case of traumatic coma. Evoked potentials performed within the first week detect approximately half of patients with a poor prognosis. EEG adds only a small amount of prognostic information.