We aim to question the concept and diagnostic criteria of Hashimoto encephalopathy (HE) or steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT) by investigating a cohort of patients with characteristics of the diagnosis.

Using Epic Slicer Dicer software, we defined a cohort of patients with positive thyroid antibodies (including anti-thyroid peroxidase, anti-thyroglobulin, thyroid stimulating immunoglobulin, and/or anti-thyrotropin receptor antibody) who underwent lumbar puncture and electroencephalography (EEG). Review of problem list/medical history defined diagnoses.  

Out of 68 patients who met inclusion criteria, 40 (58.8%) had abnormal CSF and 55 (80.9%) had an abnormal EEG including 11 (16.2%) with seizures. Diagnoses included one or more of: HE (n=7, 10.3%); other AIE (n=14, 20.6%); posterior reversible encephalopathy syndrome (PRES) (n=1, 1.5%); hepatic encephalopathy (n=1, 1.5%); CNS infection (n=5, 7.4%); unspecified encephalopathy (n=33, 48.5%); dissociative fugue (n=1, 1.5%); psychosis (n=1, 1.5%); and traumatic brain injury (TBI) (n=1, 1.5%). Thirty-eight (55.9%) had seizure/epilepsy and 38 (55.9%) had thyroid disease. Nine (13.2%) patients had positive EEG and CSF studies, but an unspecified encephalopathy.

Over time, AIE panels have expanded and HE/SREAT diagnoses have dwindled, but undefined encephalopathies with thyroid antibody positivity persist, proven by the 13.2% of patients in our study with no alternative diagnosis. Thyroid abnormalities can result in neurological symptoms and it may be beneficial for neurologists to work closely with endocrinologists for patients with this spectrum of disease.