Hashimoto’s encephalopathy mimicking spinocerebellar ataxia

Abstract

A 39-year-old man was admitted for complaints of worsening gait difficulty, weakness and dysarthria. His symptoms had developed 17 months earlier with unsteadiness of gait. Subsequently, he gradually developed difficulties in handwriting, weakness and dysarthria. His symptoms were considered as spinocerebellar ataxia in a local hospital and treated with CoQ10, and vitamins B1 and B12. No improvement was observed. His disability accelerated 2 weeks prior to admission. There is no family history of cerebellar symptoms. Physical examination revealed palpable thyroid gland. Neurological examination showed normal mental status, right central facial weakness, lingual fasciculations, brisk jaw jerk, hyperactive gag reflex and scanning dysarthria. Strength of left upper and right limbs was 4/5 with bilateral palmomental reflexes and right Babinski signs. Focal dystonia was observed in the right hand. He was only able to walk several steps, with broad-based, ataxic gait. Marked slowing and dysmetria of rapid alternating movements were noted. Pinprick and position sensations were preserved. There was no orthostatic hypotension. Magnetic resonance imaging (MRI) of the brain disclosed slight atrophy of the cerebellum without gadolinium enhancement (Fig. 1a). The electroencephalogram, Montreal Cognitive Assessment test and electromyography were normal. Cerebrospinal fluid (CSF) showed 126 mg/dl protein (normal 15–45 mg/dl) and normal IgG index. There were no oligoclonal bands (OB). Anti-GM1, GQ1b and GD1b antibodies were negative in both serum and CSF. Screenings of connective tissue disease, heavy metal and antibodies against viruses were negative. Angiotensin converting enzyme, vitamin B12, vitamin E, folate and rapid plasma reagin tests were unremarkable. Paraneoplastic antibodies were not detected in the serum. The chest CT was normal. Positron emission tomography (PET) only demonstrated a slightly decreased FDG uptake in the right thalamus (Fig. 1b). Genetic testing of SCA1-7, SCA12, SCA17 and DRPLA was negative. The patient was euthyroid with increased thyroglobulin antibody (TG-Ab) and thyroperoxidase antibody (TPO-Ab) concentrations at 83.2 U/ml (normal 0–60 U/ml) and [1,300 U/ml (normal 0–60 U/ml), respectively. Both TGAb and TPO-Ab were present in the CSF at 17.4 and 87.5 U/ml respectively. Thyroid ultrasound and scan revealed slightly enlarged thyroid gland with several hypoechoic areas and normal tracer uptake. Although antigliadin antibodies were not tested, neurological manifestations of gluten sensitivity are mainly ataxia, peripheral neuropathy, epilepsy and headache [6], which are not typical in this case. We diagnosed the condition as Hashimoto’s encephalopathy (HE) and initiated intravenous methylprednisolone 1 g/day for 5 days followed by oral prednisone tapering. Y. Tang and C. Chu contributed equally to this work.