Hashimoto's myoclonic encephalopathy: An underdiagnosed treatable condition?

Abstract

We report two patients with subacute diffuse encephalopathy characterized by confusion, myoclonic encephalopathy, and mild akineto-rigid extrapyramidal signs in one case and by apathy, memory deficit, and partial complex seizures in the other. Hashimoto's thyroiditis with high titers of anti-thyroglobulin antibodies was diagnosed in both patients, who were unresponsive to anticonvulsant medication, but showed rapid neurological improvement following steroid treatment. On neuropsychological examination, predominant frontotemporal dysfunction was noted. Electroencephalographic activity was remarkable for its rhythmical delta activity, unresponsive to, or even paradoxically increased by, anticonvulsant treatment. On magnetic resonance imaging, atrophy with temporal predominance was found. These observations support the idea that this potentially treatable dementia and movement disorder should be classified as a separate clinical entity.

Rapidly Progressive Dementia

“…Hallucinations or other psychoses are common. [72][73][74]. It is often confused with CJD because of their overlapping clinical profile.…”

“…Hashimoto's encephalopathy (HE) is a rare but probably under-diagnosed, treatable autoimmune disorder associated with chronic lymphocytic Hashimoto's thyroiditis [72,73]. Often, it begins with a prodrome of depression, personality change or psychosis and progresses into a cognitive decline associated with myoclonus, ataxia, pyramidal and extrapyramidal signs, stroke-like episodes, altered levels of consciousness, confusion and/or seizures.…”

“…MRI is not specific but commonly shows increased T2-weighted subcortical, mesial-temporal or white matter signal, which may disappear after treatment [72,[76][77][78]. CSF often has increased protein, a non-specific finding that occurs in many other RPDs, including CJD [13,72,73]. The etiology of HE but may be due to the presence of a shared antigen in the brain and thyroid [72,73,79].…”

Hashimoto

“…It is included in the list of treatable dementias [1] . The differential diagnoses include viral encephalitis, Creutzfeldt-Jacob disease, stroke, metabolic and paraneoplastic encepalopathies [2] .…”

Biomarkers of Encephalitis

“…HE is characterized by various neuropsychological symptoms, including personality changes, cognition deterioration, seizures, myoclonus and loss consciousness (Ghika-Schmid et al 1996;Henchey et al 1995;Kothbauer-Margreiter et al 1996;Mijajlovic et al 2010;Peschen-Rosin et al 1999;Shaw et al 1991). HE patients show high CSF protein levels (oligoclonal bands or an increased total protein concentration) without pleocytosis and high titer of antithyroid antibodies (Archambeaud et al 2001;Ferracci & Carnevale 2006;Hartmann et al 2000;Shaw et al 1991).…”