Focal neurological presentation in Hashimoto's encephalopathy mimicking a vascular occlusion of the middle cerebral artery.

Hashimoto's encephalopathy is a rare form of autoimmune encephalopathy. It is likely an underdiagnosed entity especially in the setting of focal neurological defects. We report a case of a 49-year-old man who presented with "strange behavior"of a day's duration. Examination was significant only for lethargy, poor attention span and agitation. Routine labs revealed leucocytosis. Head CT scan was unremarkable. Lumbar puncture showed high white blood cells with lymphocytosis and elevated protein level. The patient was empirically treated for meningitis without improvement. His symptoms progressed to sudden right-sided weakness, ataxia and right facial droop. The MRI and magnetic resonance angiogram (MRA)were normal. The patient’s focal neurological signs improved spontaneously. Encephalopathy work-up was negative except for positive anti-Thyroid Peroxidaseand antithyroglobulin. The patient was treated as Hashimoto encephalopathy with steroids and azathioprine with marked improvement. Our case highlights how focal neurological findings can potentially mislead the provider to consider vascular aetiologies in Hashimoto's encephalopathy.