Hashimoto's encephalopathy: an under diagnosed entity

Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT): Characteristics, treatment and outcome in 251 cases from the literature

BACKGROUND

Steroid-responsive encephalopathy and associated autoimmune thyroiditis (SREAT) is characterized by encephalopathy and the presence of antithyroid antibodies. We describe the clinical presentation, outcome and treatments for SREAT by a systematic review of the literature.

METHODS

MEDLINE via PubMed, Web of Science and the Cochrane Library were searched for articles published until 2015. Inclusion criteria were unexplained encephalopathy with antithyroid antibodies.

RESULTS

We found reports of 251 patients (median age 52years [range 18-86], 73% females, 80 [32%] with preexisting thyroiditis). Patients presented encephalitis signs with convulsions (n=117; 47%), confusion (n=115, 46%), speech disorder (n=91, 37%), memory impairment (n=107, 43%), gait disturbance (n=67, 27%) and persecutory delusions (n=61, 25%). Twenty-eight patients (11%) presented progressive memory impairment and 26 (10%) isolated psychiatric disorders. In serum, 34% of patients were positive for anti-thyroid peroxidase (TPO) antibodies, 7% for anti-thyroglobulin (TG) antibodies, and 69% both. Thyroid-stimulating hormone levels were usually normal, at 2 UI/ml [0.001-205]. Cerebrospinal fluid from 10/53 patients (19%) was positive for anti-TPO antibodies, 2/53 (4%) anti-TG antibodies and 28 (53%) both. Electroencephalography findings were abnormal for 82% of patients, showing diffuse slowing consistent with encephalopathy (70%) or epileptic activity (14%). The first-line treatment was steroids in 193 patients and other immunosuppressive drugs in 10 cases. At a median follow-up of 12months [range 0.2-110], 91% of patients showed complete or partial neurological response, with anti-TPO and -TG antibody titers at 347 UI/ml [0-825,000] and 110 UI/ml [0-50,892], respectively. During follow-up, 40 patients (16%) experienced at least one relapse. Relapse was more frequent in patients with initial coma (26% vs 13%, p=0.08).

CONCLUSION

The diagnosis of SREAT should be suspected in case of encephalopathy without obvious cause, to quickly start corticosteroid treatment. The exact modalities of treatment must be defined.

Altered mental status: what is the diagnosis?

We report a patient presenting with a 2-day history of altered mental status and lethargy. She had recently started taking prednisone for suspected 'autoimmune arthritis'. Clinical deterioration in hospital characterised by increasing confusion, alternating hyperarousal and somnolence, auditory hallucinations and eventual unresponsiveness led to an intensive care unit transfer. Initial laboratory and radiological testing did not reveal a cause for her symptoms. The only abnormality detected was antithyroid peroxidase antibody levels elevated to >900 IU/mL with patient demonstrating marked clinical improvement within 24 h of receiving high-dose steroids and plasmapheresis. Hashimoto's encephalitis is an underdiagnosed reversible neuropsychiatric disorder with unknown pathogenesis. Recent studies indicate that autoimmune encephalopathy and specifically Hashimoto's encephalitis is under-reported. Our case demonstrates the importance of maintaining a wide differential for altered mental status, especially after negative initial diagnostic work-up of more common aetiologies. Although steroids are an effective treatment for Hashimoto's encephalitis, the addition of early plasmapheresis may be indicated in patients with severe presentation and those who develop disease while taking steroids.