Complete heart block in nonfamilial hyperekplexia.

An infant with nonfamilial hyperekplexia had multiple episodes of tonic spasms that mimicked tonic seizures. They were accompanied by complete heart block and apnea. These episodes did not correlate with electroencephalographic epileptiform changes and were partially responsive to clonazepam, valproic acid, and cardiac pacemaker. Sudden death in hyperekplexia may be related to complete heart block and apnea during seizurelike episodes.