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A 50 year old man developed tonic-clonic seizures while receiving cyclosporin A after orthotopic cardiac transplant. The seizures resolved after cessation of cyclosporin A. Thirteen months later, he developed diplopia from bilateral internuclear ophthalmoplegia while receiving intravenous FK506. A temporal association was found between his symptoms and the serum FK506 concentrations. Withdrawal of the intravenous FK506 led to prompt resolution of the bilateral internuclear ophthalmoplegia.

Background: In chronic petrol sniffers, recent exposure to high levels of leaded petrol may give rise to a lead encephalopathy characterised by tremor, chorea, ataxia, hyperreflexia, convulsive seizures, and death. Neurological abnormalities associated with lead encephalopathy involve the cortex, basal ganglia, cerebellum, and brain stem., Objective: To use saccadic eye movement tasks as an experimental tool to determine which CNS changes are associated with chronic petrol sniffing and which with a history of lead encephalopathy, and to what extent these changes are reversible., Methods: Saccade function was assessed in chronic petrol sniffers with a history of lead encephalopathy (encephalopathic sniffers), chronic petrol sniffers who had never suffered lead encephalopathy (chronic sniffers), individuals who had sniffed petrol in the past but had not done so for more than six months (ex-sniffers), and individuals who had never sniffed petrol (non-sniffers)., Results: Chronic sniffers showed increased latency of visually guided saccades and antisaccades and increased antisaccade errors which suggested cortical and basal ganglia dysfunction. These abnormalities returned to normal in ex-sniffers. Encephalopathic sniffers showed the same abnormalities as chronic sniffers but with greater severity and additional saccadic signs including dysmetria, gaze evoked nystagmus, and saccade slowing which usually indicate cerebellar and brain stem dysfunction., Conclusions: Chronic petrol abuse is associated with cortical and basal ganglia abnormalities that are at least partially recoverable with abstinence. Additional long term cerebellar and brain stem abnormalities are associated with lead encephalopathy.

A 52 year old man developed a supranuclear gaze palsy and opsoclonus after Diazinon poisoning. The diagnosis was confirmed by low plasma and red blood cell cholinesterase activity and urine mass spectroscopy. Saccadic control may be mediated in part by acetylcholine. Opsoclonus in the setting of organophosphate intoxication may occur as a result of cholinergic excess which overactivates the fastigial nuclei.