Nonmetabolic causes of triphasic waves: a reappraisal.

Two more patients with triphasic waves (TW) on their EEGs in the absence of metabolic disturbances are described. One patient had coma associated with cerebellar hematoma, the other had mild dementia associated with idiopathic calcifications of the basal ganglia and normal auditory brainstem responses, subcortical and cortical somatosensory evoked potentials. Neurologic examination failed to show asterixis in both patients. The literature on nonmetabolic causes of TW was also reviewed, and the clinical and anatomic reports of 10 patients have been analyzed: 7 patients had focal brainstem-diencephalic lesions (craniopharyngioma: 2 patients; thalamic gliomas: 3 patients; pontine stroke: 2 patients), and 3 patients suffered from diffuse subcortical or multifocal encephalopathies (Binswanger's encephalopathy: 1 patient; cerebral carcinomatosis: 1 patient; multifocal cerebral lymphoma: 1 patient). From the clinical point of view, patients with nonmetabolic diseases causing TW presented either disturbance of higher cerebral functions with no asterixis or sudden onset of coma. It is concluded that TW may result from focal brainstem/diencephalic lesions or from diffuse subcortical or multifocal encephalopathies in the absence of concomitant metabolic abnormalities. Nonmetabolic causes of TW should be suspected in patients presenting with neurologic disturbances not associated with asterixis.