Opsoclonus Due to Diphenhydramine Poisoning

Opsoclonus consists of involuntary, irregular, back-to-back, multivectorial, saccadic eye movements while the gaze is fixed. It is seen primarily in association with autoimmune processes after viral infection and with paraneoplastic encephalitis but has also been described after ingestion of organophosphates, lithium, cetirizine, amitryptiline, diphenhydramine, or other substances.