The neuromythology of Hashimoto encephalopathy

The initial description of Hashimoto encephalopathy (HE) is credited to Lord Brain and his colleague Jellinek,¹ who in 1966 reported a patient with an “extraordinary and puzzling neurologic illness which waxed and waned for over a year.” The patient was a 48-year-old man who had been previously diagnosed with Hashimoto thyroiditis. Just over a year later, he developed an episodic neurologic illness characterized by alteration in mood and consciousness and stroke-like episodes variably inducing transient aphasia, right or left hemiparesis, hemi-sensory deficits, hemianopsia, and monocular blindness. These were followed by episodic hallucinations, agitated confusion, and involuntary movements (tremor, athetosis). Multiple CSF examinations were remarkable only for an elevated protein (maximal 240 mg/dL) and at times a paucicellular pleocytosis (never >8 cells/mm³). Carotid angiography was unremarkable. An EEG showed generalized theta and delta slowing. Neuroimaging was not performed. He was treated intermittently with prednisone and an anticoagulant with little consistent response. Changes in serum thyroid antibodies seemed to parallel the clinical course. The illness resolved spontaneously. Lord Brain and Jellinek summarized the case as one of a “stuttering brain disorder of an unusual kind with concurrent rise in the level of thyroid antibodies.”¹