Endocrine encephalopathy.

The diagnosis of Hashimoto's encephalopathy is made when no other cause is found for an acute encephalopathic illness, in the presence of positive thyroid autoantibodies, and is supported by a response to steroid therapy. A 59-year-woman developed an encephalopathic illness with mixed aphasia, global weakness and generalised seizures requiring intubation and ICU admission. Extensive imaging and laboratory investigations looking for an underlying cause for the encephalopathy were unremarkable. Thyroid autoantibodies were strongly positive, raising the possibility of Hashimoto's encephalopathy. Thyroid function testing showed profound primary hypothyroidism. The patient was commenced on high-dose methyprednisolone, with prompt cessation of seizure activity. Thyroxine replacement was commenced, with the methyprednisolone switched to oral prednisone and slowly weaned. The patient had no further seizures and ultimately made a full recovery.