To illustrate a case of varicella zoster virus (VZV) cerebellitis and highlight the importance of an infectious evaluation in adults with subacute cerebellar ataxia.

Neurological manifestations of VZV reactivation are diverse. Although more commonly seen in children, VZV cerebellitis is a disease process that can also occur in adults and may present without a typical dermatomal rash.

A 59-year-old male with a past medical history significant for tobacco dependence presented due to three days of progressive gait instability and falls. The patient was afebrile with normal vital signs. On neurological examination, he had severe truncal ataxia without dysmetria; he was unable to sit or stand without assistance. No rash was present on skin exam.

Head computed tomography demonstrated mild ventriculomegaly with features suggestive of normal pressure hydrocephalus. Brain magnetic resonance imaging with gadolinium showed no additional abnormalities. A lumbar puncture was performed which showed total nucleated cells at 104 cells/mcL (82% lymphocytes), protein of 57 mg/dL, elevated IgG index of 1.00, and 6 supernumerary oligoclonal bands. Paraneoplastic autoantibody evaluation and cytology analysis were normal. Microbiological evaluation revealed a positive cerebrospinal fluid VZV polymerase chain reaction and positive serum VZV IgM and IgG; other microbiological testing was negative.

The patient was diagnosed with VZV cerebellitis and started on a ten-day course of intravenous acyclovir. He demonstrated marked improvement after three days of treatment. At his 2-month follow-up evaluation he was able to walk unassisted and had no features of ataxia on exam.   

Acute VZV cerebellitis is a treatable neurological disorder that should be considered in adults with rapid onset cerebellar ataxia. Cerebellar ataxia is one of many neurological complications of VZV reactivation that may be seen in the absence of a rash.