2452 Tick-borne encephalitis presenting as hemichorea

Introduction Tick-borne encephalitis (TBE), caused by infection with Flaviviridae vector-borne viruses, is a rising health concern in parts of the world.¹ TBE viruses may cause meningitis, encephalitis, myelitis and polyradiculitis.² We describe an unusual presentation of TBE with chorea.

Methods Case report.

An 82 year-old female presented with acute right-sided hemichorea and confusion. Her background was significant for treated polymyalgia rheumatica, hypertension on verapamil and restless legs syndrome on pramipexole. She described numerous tick bites across her scalp three weeks prior to presentation, treated with a week’s course of doxycycline. Examination revealed severe right-sided chorea with no other extrapyramidal signs.

Results There was no stroke, or other cause for her symptoms on MRI. The CSF was abnormal with a mononuclear pleocytosis (30 x 10⁶/L), normal protein, negative culture and negative multiplex PCR for viruses. Serological and CSF work-up for alternate causes of chorea was negative. An FDG-PET CT brain demonstrated no regional cerebral glucose hypometabolism. After exclusion of all other causes, she was diagnosed with encephalitis with hemichorea. Following treatment with intravenous pulse methylprednisolone her symptoms resolved one week later.

Conclusion To our knowledge there are only two other case reports of TBE causing chorea.^{2 3} This is the first case reported in Australia. The mechanism of chorea remains unclear, but responded to immunotherapy so quickly and comprehensively that neuronal molecular mimicry with a viral or bacterial pathogen, or venom protein seems more likely than a productive viral infection.

References

1. European Centre for Disease Prevention and Control. Epidemiological situation of tick-borne encephalitis in the European Union and European Free Trade Association countries. Stockholm: The Centre; 2012.

2. Zajkowska J, Moniuszko A, Czupryna P, et al. Chorea and Tick-Borne Encephalitis, Poland. Emerg Infect Dis, 2013;19(9):1544–1545.

3. Bender A, Schulte-Altedorneburg G, Walther EU, Pfister HW. Severe tick borne encephalitis with simultaneous brain stem, bithalamic, and spinal cord involvement documented by MRI. J Neurol Neurosurg Psychiatry, 2005;76:135–137.