Abstracts

Rationale: Hashimoto’s encephalitis (HE) is a rare cause of epilepsy. Behavioral changes and encephalopathy frequently precede other symptoms. Seizures and status epilepticus may be the first manifestation of HE. Diagnosis could be delayed due to its relapsing-remitting course consistent with its autoimmune nature. Three patients who presented with new onset seizures or status epilepticus, and in whom diagnosis of HE was considerably delayed, are described.Methods: We identified 3 consecutive women (mean age 45.6 years) in whom HE was diagnosed 3 weeks to 10 months from the onset of symptoms. All presented with mood and mental status changes and new onset seizures or status epilepticus.Results: The first patient is a 28 year old woman with new onset encephalopathy who was found to be in status epilepticus during continuous video-EEG (cVEEG) monitoring. She was unsuccessfully treated with anti-seizure medications and eventually with steroids for presumed autoimmune or paraneoplastic encephalitis. Her symptoms subsided initially but recurred several times over 10 months until a diagnosis of HE was made. The second patient is a 65 year old woman with history of hypothyroidism who presented with mental status changes and paranoia. cVEEG recorded several electrographic ictal discharges. Her symptoms remitted transiently after steroids were initiated for presumed autoimmune encephalitis. She experienced several exacerbations over 8 weeks which eventually prompted assessment of anti-thyroid antibodies. The third case is a 44 year woman who presented with a focal motor seizure and intermitted mental status changes. Her symptoms persisted over a period of 2 weeks before a diagnosis of HE was made. All patients had an extensive initial work up which was negative. When anti-thyroid antibodies were ordered, weeks to months after the initial presentation, these were found to be abnormally elevated. All 3 patients responded to steroid treatment and/or immunomodulation.Conclusions: Hashimoto’s encephalitis can present with a variety of manifestations and is probably significantly undiagnosed. It should be considered in cases presenting with new onset seizures or status epilepticus in the context of mental status and mood changes. While evaluation for other autoimmune disorders should be carried out, assessment of anti-thyroid antibodies should also be undertaken upon initial evaluation. Patients are usually unresponsive to anticonvulsant therapy and tend to respond well to steroid treatment and immunomodulation. Delaying the diagnosis could have a negative impact on patient’s outcome, increase morbidity, affect hospital length of stay as well as increase healthcare costs.