Teaching NeuroImage: Plexus Neuritis After an Infection With the Tick-Borne Encephalitis Virus

A 71-year-old man presented with an impaired range of motion and pain in his left arm that had progressed for 8 days, accompanied by headaches and neck pain. He recalled a tick bite 1 month earlier. Clinical examination revealed a complete motor palsy of the left arm (0-1/5 in all muscles) and weakened reflexes of the upper and lower limbs (0-1/4). Electrophysiologic examinations showed signs of axonal damage to the radial, ulnar, and median nerves on the left. An MRI examination did not show any acute lesions of the meninges, brain, or spinal cord. The CSF showed lymphocytic pleocytosis and antibodies against tick-borne encephalitis virus (TBEV).(1) The CSF and blood samples were negative for borrelia. An MRI of the brachial plexus(2) showed bilateral inflammation of trunks and fascicles (Figure). The findings show that TBEV infection may cause plexitis after tick bites.