Diagnosis
Laboratory and radiological findings
Increased liver enzyme levels (55% cases)
Increased thyroid-stimulating hormone (55% cases)
Increased erythrocyte sedimentation rate (25% cases)Cerebrospinal fluid findings:
Raised protein (25% cases)
Negative for 14–3–3 protein
May contain antithyroid antibodies
Magnetic resonance imaging abnormalities consistent with encephalopathy (26% f cases)
Single photon emission computed tomography shows focal and global hypoperfusion (75% of cases)
Cerebral angiography is normalThyroid hormone abnormalities are common (>80% of cases):
Subclinical hypothyroidism (35% of cases)
Overt hypothyroidism (20% of cases)
Hyperthyroidism (5% of cases)
Euthyroid on levothyroxine (10%  of cases)
Euthyroid not on levothyroxine (20% of cases)Thyroid antibodies – both antithyroid peroxidase antibodies (anti-TPO, antithyroid microsomal antibodies, anti-M) and antithyroglobulin antibodies (anti-Tg) – in the disease are elevated, but their levels do not correlate with the severity.Electroencephalogram studies, while almost always abnormal (98% of cases), are usually not diagnostic. The most common findings are diffuse or generalized slowing or frontal intermittent rhythmic delta activity. Prominent triphasic waves, focal slowing, epileptiform abnormalities, and photoparoxysmal and photomyogenic responses may be seen.A study from 2006 suggested the following diagnostic criteria:
Encephalopathy with cognitive impairment and at least one of the following features:
neuropsychiatric symptoms (e.g. hallucination, delusion or paranoia)
Myoclonus, generalised tonic-clonic or partial seizures
focal-neurological deficits
Elevated titres of thyroid tissue antibodies (TPO-ab or microsomal)
Euthyroidism (potentially achieved by treatment with L-T4 or L-T3) or mild hypothyroidism with TSH concentration below 20 mIU/L
No evidence for infectious, toxic, metabolic or neoplastic processes in blood, urine or CSF analyses
No serological evidence for neuronal antibodies (e.g.
Earlier reports suggested that 90% of cases stay in remission after discontinuation of treatment, but this is at odds with more recent studies, which suggest that relapse commonly occurs after initial high-dose steroid treatment. Left untreated, this condition can result in coma and death. Epidemiology
The prevalence has been estimated to be 2.1/100,000 with a male-to-female ratio of 1:4. The mean age of onset is 44 with 20% of cases presenting before the age of 18 years. Most reported cases occur during the patients fifth decade of life. History
The first case of HE was described by Brain et al. in 1966. The patient was a 48-year-old man with hypothyroidism, multiple episodes of encephalopathy, stroke-like symptoms, and Hashimotos thyroiditis confirmed by elevated antithyroid antibodies. Alternative names
Steroid-responsive encephalopathy associated with autoimmune thyroiditis, SREAT
Nonvasculitic autoimmune meningoencephalitis, NAIM
Encephalopathy associated with autoimmune thyroid disease, EAATD

References
Further reading
Hashimotos Encephalopathy SREAT Alliance (2013). Understanding Hashimotos Encephalopathy: A Guide for Patients, Families, and Caregivers, Featuring Stories of HE Patients from Around the World. North Charleston, SC: CreateSpace Independent Publishing Platform. ISBN 9781484883099. OCLC 890816771. Schiess N, Pardo CA (October 2008). "Hashimotos encephalopathy". Annals of the New York Academy of Sciences. 1142 (1): 254–65. Bibcode:2008NYASA1142..254S. doi:10.1196/annals.1444.018. PMID 18990131. S2CID 1312798. Taylor SE, Garalda ME, Tudor-Williams G, Martinez-Alier N (February 2003). "An organic cause of neuropsychiatric illness in adolescence". The Lancet. 361 (9357): 572. doi:10.1016/S0140-6736(03)12517-2. PMID 12598143. S2CID 35053683.