Case Presentation: The patient is a 70 y.o. female with a history of hypertension, bilateral lower extremity deep vein thrombosis (DVT), and peripheral neuropathy, who was brought to the emergency room (ER) by EMS due to the recent onset of altered mental status. Starting a few days ago, her son noted that she was not oriented to time. Also, for the past week, she has complained of fatigue and a poor appetite.
Initial vital signs were T 36.6, BP 210/106, heart rate 76, respiratory rate 18, and room air oxygen saturation level 99%. Her physical examination was limited by her inability to cooperate, since she was drowsy, agitated, and completely disoriented. The patient moved all of her extremities well, and she grimaced and withdrew from noxious stimuli. Her head CT scan, and routine laboratory studies, including a CBC and comprehensive metabolic panel were unremarkable.
Right facial twitching was noted in the ER, and her electroencephalogram (EEG) showed evidence of seizure activity. She was started on levetiracetam and phenytoin. Her brain MRI showed an extensive abnormal brain parenchymal signal, as well as leptomeningeal enhancement affecting the cerebral hemispheres, basal ganglia, and cerebellum. A lumbar puncture was performed, and her cerebrospinal fluid (CSF) contained 20 WBCs/μL (84% neutrophils). CSF protein was 115 mg/dL. Her brain MRI findings in combination with the CSF results were suggestive of acute infectious meningoencephalitis. Therefore, intravenous (IV) vancomycin, ampicillin, acyclovir, and ceftriaxone were started empirically.
The Infectious Diseases (ID) service ordered an extensive work up to identify a causative pathogen, including the following tests from her CSF: routine culture, HSV PCR, fungal culture, Cryptococcus antigen, VDRL, West Nile antibody, and Enterovirus PCR. All of these tests were negative, and this raised concern for possible autoimmune encephalitis. To this end, anti-thyroid peroxidase antibody and thyroglobulin antibody levels were ordered, and they were both elevated, at 61 and 86.3 units/mL, respectively. Intravenous methylprednisolone was started, and within 36 hours, her mental status had markedly improved. After 5 days, IV methylprednisolone was discontinued, and oral prednisone was started. When she was discharged on hospital day 14, she was fully intact neurologically, having returned to her normal baseline.
Discussion: Hashimoto encephalopathy is an uncommon disorder that may accompany Hashimoto thyroiditis. It occurs more commonly in females than males, and it is typically associated with seizures, myoclonus, an altered level of consciousness, and confusion. Hashimoto encephalopathy is thought to be an immune-mediated disorder, but the precise mechanism is uncertain. Most patients with HE are euthyroid. The diagnosis of Hashimoto encephalopathy is based on elevated anti-thyroid peroxidase antibody and thyroglobulin antibody levels, in patients with congruent clinical findings. Steroids are effective for treatment of Hashimoto encephalopathy in 90 to 98 percent of patients, with symptom improvement or resolution usually noted within a few months.
Conclusions: Hashimoto encephalopathy should be considered in patients (especially females) who present with an altered level of consciousness, seizures, or other signs of encephalopathy that are not due to an infectious etiology. Most patients respond well to treatment with steroids.