Status epilepticus in Hashimoto's encephalopathy

Hashimoto's encephalopathy is a non-infectious, probably autoimmune encephalitis, characterized by varied signs coupled with elevated levels of anti-thyroid antibodies and, often, good response to corticosteroid therapy. Seizures, namely focal and generalized tonic-clonic seizures, myoclonus, and status epilepticus, are frequent manifestations of Hashimoto's encephalopathy. Typically, seizures in these patients respond poorly to anti-epileptic drugs. Although cases of Hashimoto's encephalopathy with status epilepticus have been reported in literature, they vary in demographic, clinical, and treatment characteristics. We could not identify any systematic review summarizing the evidence in regard to factors predicting the occurrence of status epilepticus in Hashimoto's encephalopathy and the responsiveness of status epilepticus to anti-epileptic drugs, steroids and other immunomodulatory medication. Therefore, we performed an extensive review of the literature to identify and compare Hashimoto's encephalopathy patients presenting with and without status epilepticus. In 31 patients with status epilepticus and 104 patients without status epilepticus, thyroid status, anti-thyroid antibodies, cerebrospinal fluid analysis, brain MRI/CT/SPECT scan did not predict occurrence of status epilepticus of variable phenomenology. Status epilepticus did not respond to anti-epileptic drugs but completely remitted under steroid treatment, alone or in combination with other immunomodulatory medication, in about three quarter of patients. Generalized convulsive status epilepticus might be a factor negatively influencing outcome.