VZV CNS Infection Testing

UCSF Neurology/Infectious Diseases Diagnostic Testing Recommendations For Patients with Suspected CNS VZV Infection

Clinical Indications for Testing:

1. Meningitis of unknown etiology, especially with rash suspicious for VZV or with stroke of unknown etiology
2. Encephalitis/meningoencephalitis of unknown etiology
3. Vasculopathy and strokes with CSF inflammation
4. Myelitis of unknown etiology
5. Lumbosacral or brachial plexopathy of unknown etiology

For patients in whom CNS VZV infection is suspected:

1. Send CSF VZV PCR and CSF VZV IgG.
   1. CSF VZV PCR can be an insensitive test for diagnosis of certain forms of CNS VZV infection, such as VZV vasculopathy or presentations evaluated more than 1 to 2 weeks after symptom onset. PCR is most useful early in the course.
   2. Intrathecal VZV IgG usually becomes detectable about 7 days after symptom onset and provides an additional diagnostic tool. In VZV vasculopathy, intrathecal VZV IgG has a sensitivity of > 90%, compared with about 30% for PCR.
   3. Detection of CSF VZV IgG supports CNS VZV infection. In some cases (e.g., after IVIG, with a traumatic tap, blood-brain barrier disruption, or presence of another CNS inflammatory process) calculating a VZV antibody index may be helpful to confirm intrathecal synthesis. This requires CSF and serum VZV IgG as well as CSF and serum albumin or total IgG, ideally drawn the same day as the lumbar puncture. Interpret results with caution in immunosuppressed patients, who may not mount a detectable antibody response.
2. Consider sending CSF VZV IgM in addition to CSF VZV PCR and CSF VZV IgG in selected patients with an acute presentation. CSF VZV IgM may provide supportive evidence of recent infection or reactivation, but data on its diagnostic performance are limited, and a negative CSF result does not exclude CNS VZV infection