The diagnosis of Hashimoto encephalitis is one of exclusion. Thyroid antibodies (anti-TPO being the most common) are typically present and in high levels. The clinical presentation varies with most common symptoms included Seizures (63%) and cognitive impairment (85%). EEG studies on Hashimoto encephalitis reported generalized slow wave abnormalities, triphasic waves, sporadic epileptiform abnormalities, photomyogenic response, and photoparoxysmal response.

Lateralized periodic discharges (LPDs) have been associated with focal central nervous system lesions. By far the most common etiology is cerebrovascular disease (ischemic, hemorrhage) followed by mass lesion and infections.

Case Presentation:

We report a 59-year-old female with sudden onset decrease level of consciousness, left gaze deviation and global aphasia. EEG on day one showed independent continuous bitemporal (First left then migrated to right) LPDs. Serological studies showed high levels of anti-TPO antibodies and the diagnosis of Hashimoto encephalitis was made in combination with the exclusion of other etiologies of encephalopathy. MRI Brain showed subtle right temporal FLAIR hyperintesity. She received intravenous methylprednisolone for five days, IV Immunoglobulin and anti-epileptic medication with minimal improvement. Hospital course was complicated by cystitis, pyelonephritis and her repeat EEG monitoring showed a migratory pattern of LPDs involving right frontopolar and left posterior quadrant independently. These LPDs then proceeded to migrate to various regions of the brain throughout her hospitalization. Repeat MRI Brain showed multifocal supratentorial and infratentorial cortical and subcortical FLAIR hyperintensities. Oral steroids were started and broad spectrum antibiotics were initiated. After approximately three weeks of hospitalization she started to improve neurologically.