Pseudoperiodic bilateral EEG paroxysms in a case of phencyclidine intoxication.

A 23-year old white man presented an acute PCP intoxication. His EEG showed a monomorphic nonreactive generalized theta rhythm which is the typical activity of PCP overdose. This background was interrupted by periodic bilaterally synchronous high voltage slow paroxysms similar to those described in subacute sclerosing panencephalitis. This unusual finding supports the hypothesis that PCP may act by reversible deafferentation of cortical neurons.