A 60-year old female with past medical history significant for diabetes, hypertension, and hypothyroidism presented with acute onset confusion progressing over the course of 5 hours. On exam, patient’s vitals were significant for an elevated blood pressure (179/104). She was only oriented to herself and showed no focal motor deficits, but did have a rhythmic twitching of her right great toe. Electrolytes and glucose were within normal limits. Computer tomography of the head was negative for hemorrhage, MRI brain demonstrated small, left occipital stroke but was without mass or findings of edema characteristic for posterior reversible encephalopathy syndrome. EEG was significant for slowing of the left frontal-temporal lobe, consistent with a post-ictal state. Patient developed worsening seizure-like movements and was intubated for airway protection. The extent of the patient’s symptoms was not explained by her small, occipital stroke; a lumbar puncture was performed with: no evidence to suggest bacterial, viral, or fungal infection. Glucose and protein levels were normal. Oligoclonal bands and myelin basic protein were negative. Thyroid stimulating hormone was slightly elevated at 8.056uIU/mL with a normal free T4. Anti-thyroid microsomal antibodies was elevated at 119.51IU/mL (normal <5.61IU/mL). Based on the patient’s constellation of symptoms, not explained by other identifiable cause, she was started on high-dose steroids for treatment of possible Hashimoto’s encephalopathy for a total of 5 days. She responded well and returned to her baseline mental status within 24 hours.
Discussion:
Hashimoto’s encephalopathy (HE), also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis, is a rare condition (estimated prevalence of 2.1/100,000, 4:1 ratio of female to male) first described in 1966, which is associated with autoimmune thyroiditis. However, the HE does not appear to be directly related to the condition of the thyroid, as a majority of patients are euthyroid at presentation. HE can lead to a myriad of symptoms including: seizures (53%), confusion (43%), myoclonus (37%), cognitive impairment (36%), altered consciousness (36%), psychiatric disorders (30%), and has even been associated with stroke in case reports. The diagnosis is one of exclusion, but requires the presence of thyroid autoantibodies, symptoms of encephalopathy, and clinical improvement with administration of steroids. HE can have a variable clinical course: it may be recurrent with multiple acute episodes or more slowly progressive. While prognosis is generally favorable, patient who experience a delay in treatment may have long-standing deficits and some patients require continuous steroid or other immunomodulatory treatment to retain remission.
Conclusions:
Hashimoto’s encephalopathy should be considered in the differential in patients presenting with altered mentation and other neurological findings that are otherwise unexplained.