Recurrent encephalopathy and generalised seizures associated with relapses of thyrotoxicosis.

Seizures or encephalopathy associated with thyrotoxicosis are very rare. A 30-year-old man with thyrotoxicosis and strongly positive thyroid antibodies presented with generalised seizures preceded by an encephalopathic illness of a few days duration. CSF protein was raised and EEG showed bilateral slowing of activity. Antithyroid drug treatment rendered him biochemically euthyroid, his cognitive state returned to normal and his seizures stopped. Subsequently he had a recurrence of both encephalopathy and seizures on two occasions, coinciding with relapses of the thyrotoxicosis. This supports the view that the hyperthyroid state caused this serious neurological condition. Treatment with 131I caused hypothyroidism and he has remained seizure free and well for six years on thyroxine replacement. Corticosteroids may have been helpful in the management of his encephalopathy.