Hashimoto's encephalitis - A case report

A 50 year-old woman with a background of focal epilepsy presented to Emergency Department (ED) in convulsive status epilepticus. After 1 year seizure-free on levetiracetam,she initially presented with headache, tremor, fatigue and general malaise. She was discharged, then re-presented to ED several days later in status epilepticus. Two doses of diazepam administered pre-hospital failed to terminate the seizure. She was loaded with phenytoin,intubated and ventilated and commenced on a midazolam infusion. She spent 7 days in neuro-intensive care and was discharged home on levetiracetam 1.5 g twice daily and phyentoin 250 mg twice daily. One month later, she re-presented to ED with 4 days of worsening tremors and reduced mobility. Physical examination revealed multifocal myoclonus. She had experienced significant cognitive decline and neuropsychiatric symptoms including severe anxiety, delusions and paranoia. Investigations Imaging Initial MRI head with gadolinium showed marked symmetric abnormality within the white matter of both hemispheres extending into subcorticol regions, most predominant at the vertex and involving U fibres. The neuro-radiologist commented that the differential for these changes was broad, including an encephalitis, PML, meningitis or a leukoencephalopathy. Repeat MRI head 1 month later showed complete resolution of the white matter changes leaving no sequelae. Blood tests Her past medical history included subclinical hypothyroidism. Thyroid function tests showed an elevated TSH of 21.33 and thyroid peroxidase(TPO) antibody level of 188.0 IU/mL, with FT4 levels within normal range. Extensive relevant blood screen, including the following was all negative • NMDA, glycine receptor and anti-cardiolipin antibody • Connective tissue screen, anti-MPO and anti-PR3 • Serum electrophoresis • Paraneoplastic antibody screen including Cerebellum IIF, MA2, MA1, amphiphysin, CV2(CRMP5), Anti-Ri (ANNA 2) Ab, Anti Yo Ab and Anti Hu Ab • HIV and syphilis serology • JC virus • Plasma amino acid, urine organic acid and ammonia Lumbar puncture CSF WCC 1/mm3 CSF protein- 816 mg/L CSF viral PCR (including JC virus) and oligoclonal bands negative EEG- normal background activity with no clear focal or diagnostic epileptiform abnormalities. Treatment and follow-up The clinical picture, elevated TPO antibodies and absence of other relevant investigation abnormality raised Hashimoto's encephalitis as a potential unifying diagnosis. She had a good response to inpatient treatment with steroids, her neuropsychiatric features resolved and she has remained seizure-free since discharge. She remains under neurology outpatient follow-up. Discussion: It can be challenging to make a diagnosis of Hashimoto encephalitis, and other potential causes such as infection, metabolic or paraneoplastic processes must be rigorously ruled out (1). In this case, high titres of TPO alongside the clinical presentation with recurrent seizures and cognitive decline were key in making the diagnosis (2,3). Due to an overlap of features, including myoclonus and rapid cognitive decline, it was important to consider Creutzfeldt-Jakob disease (CJD) in the differential. We ruled out CJD due to the rapid response to steroid therapy and lack of typical EEG and MRI findings (4). Overall, due to low prevalence and non-specific MRI and EEG features, this diagnosis can be difficult to make and requires thorough systemic clinical assessment.