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

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

	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
Risk factors	• Can occur in previously health individuals	• Incorrect dosing
Clinical characteristics^a	• 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 IgG^b
	• Elevated serum or CSF CMMG^c
Treatment	• Acyclovir or valacyclovir	• Cessation of acyclovir
Treatment	• Acyclovir or valacyclovir	• Hemodialysis
Clinical course	• Variable resolution	• Full resolution over 1–5 days
Clinical course	• Chronic neurologic sequelae may occur	• Full resolution over 1–5 days

Abbreviations: CMMG 9-Carboxymethoxymethylguanine, CSF Cerebrospinal fluid, Ig Immunoglobulin, PCR Polymerase chain reaction, VZV Varicella zoster virus
^aThese are more classic presentations. There is considerable clinical overlap in these two diagnoses.
^bPositive CSF anti-VZV IgM and IgG may take several days or weeks to develop and would require repeat lumbar puncture.
^cElevated serum and CSF CMMG levels are suggestive of acyclovir-induced neurotoxicity [10].

ISSN: 1752-1947