Encéphalopathie de Hashimoto : une cause rare d'état de mal épileptique

Hashimoto's Encephalopathy (HE) is a rare condition defined by the association of encephalopathy and autoimmune thyroiditis with increased levels of antithyroid antibodies. Presenting symptoms of HE may be quite variable. Although seizures are rather frequent, status epilepticus seems very rare (10 reported cases to date) and exceptionally revealing. We report the case of a 48-year-old female, who presented with a series of status epilepticus. The only positive result of the initial exploration was an increased level of antithyroid antibodies. The patient's condition improved only after initiation of corticosteroid treatment, which provided a stable remission. HE pathophysiology still remains poorly understood and controversial. Pathological data are sparse and provide variable pictures. Although an autoimmune mechanism looks very likely, the precise role of antithyroid antibodies is still discussed. A direct toxicity has not been demonstrated and antibodies could simply be a marker of impaired immunity. Occurrence of status epilepticus in HE could be related to the presence of active inflammation of cortical or para-cortical tissue, although such a hypothesis remains to be demonstrated. The diagnosis of HE should be systematically considered in patients with unexplained episodes of status epilepticus. Search for abnormal thyroid function and increased levels of antithyroid antibodies allow both early diagnosis and treatment, with a clear benefit for the patients.