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Table 1 Clinical characteristics of varicella zoster virus encephalitis compared with acyclovir-induced neurotoxicity

From: Acyclovir-induced neurotoxicity with a positive cerebrospinal fluid varicella zoster PCR result creating a management dilemma: a case report

  VZV encephalitis Acyclovir-induced neurotoxicity
Timing of onset • Variable temporal association with cutaneous zoster and primary infection • Close temporal association with initiation of acyclovir
Risk factors • Immunocompromised state • Impaired renal function
• Can occur in previously health individuals • Incorrect dosing
Clinical characteristicsa • Headache • Acute encephalopathy
• Acute encephalopathy • Tremor, myoclonus
• Fever • Agitation
• Nausea and vomiting • Hallucinations
• Cutaneous zoster may be present • Dysarthria
CSF studies • CSF pleocytosis • Often normal
• Positive CSF VZV PCR • May have CSF pleocytosis [7] or positive VZV PCR [8]
• Positive CSF anti-VZV IgM or IgGb
• Elevated serum or CSF CMMGc
Treatment • Acyclovir or valacyclovir • Cessation of acyclovir
• Hemodialysis
Clinical course • Variable resolution • Full resolution over 1–5 days
• Chronic neurologic sequelae may occur
  1. Abbreviations: CMMG 9-Carboxymethoxymethylguanine, CSF Cerebrospinal fluid, Ig Immunoglobulin, PCR Polymerase chain reaction, VZV Varicella zoster virus
  2. aThese are more classic presentations. There is considerable clinical overlap in these two diagnoses.
  3. bPositive CSF anti-VZV IgM and IgG may take several days or weeks to develop and would require repeat lumbar puncture.
  4. cElevated serum and CSF CMMG levels are suggestive of acyclovir-induced neurotoxicity [10].