Case Presentation: 62-year-old male admitted following new onset generalized tonic clonic seizure lasting 5-6 minutes witnessed by mother. Per EMS on scene, he was agitated and required ketamine and midazolam while on route to the hospital. Upon admission, he was hemodynamically stable with physical exam only remarkable for raised maculopapular rash extending from the left chest wall to left axilla in a dermatomal distribution. He had no focal neurological deficits. Per neurology, he was loaded with IV levetiracetam 2g and started on maintenance levetiracetam 750mg BID due to prolonged duration of seizure. Workup significant for pure anion gap metabolic acidosis of 21 mmol/L with lactic acidosis of 8.4 mmol/L, UDS positive for benzodiazepine and cannabinoids. CT head without contrast without acute intracranial hemorrhage or mass effect. Given suspicion for possible VZV meningoencephalitis, he underwent LP and was started on IV acyclovir 10 mg/kg every 8 hours while awaiting CSF fluid results. His CSF studies returned with 94% lymphocytes, protein of 58 mg/dL, and glucose of 82 mg/dL. No organisms were seen on CSF culture. Subsequent PCR analysis of the CSF was positive for varicella zoster virus (VZV), indicating VZV meningoencephalitis. MRI brain showed increased T2 signal in mesial temporal lobes bilaterally without restricted diffusion, hemorrhage, or enhancement, likely etiology of seizure. His HIV testing was negative. He continued on IV acyclovir and was transitioned to oral valacyclovir 2g q6hrs once his skin lesions crusted over for 14 days of treatment.
Discussion: VZV is a herpes virus commonly known to cause varicella (chickenpox) in primary infection. After infection, the virus remains latent in the ganglia of the nervous system, causing herpes zoster (shingles) upon reactivation. Patients with herpes zoster typically develop a painful unilateral rash spanning 1-2 adjacent dermatomes. Uncommonly, patients can develop meningitis, encephalitis, and/or have disseminated zoster where >3 dermatomes are affected. While VZV is a common cause of aseptic meningitis and viral encephalitis, it is a rare etiology of meningoencephalitis in an immunocompetent host. (1)Even though our patient did not have classic symptoms of nuchal rigidity, fever, and headache typically seen with aseptic meningitis, he was able to receive prompt antiviral treatment due to his rash. Given only 1.2 percent of patients with aseptic meningitis undergo a CSF VZV PCR,(2) it is likely VZV meningoencephalitis is underdiagnosed, especially in immunocompetent patients. This is suspected to be from lack of recognition, atypical presentation including lack of characteristic rash, and low sensitivity of CSF PCR to detect VZV.(3) This is concerning as VZV meningoencephalitis may be missed, which could lead to delay in treatment and subsequent long-term neurologic sequelae and/or mortality despite available treatment options.
Conclusions: VZV meningoencephalitis is a rare complication of herpes zoster especially in the immunocompetent population that may be missed if patients do not present with classical symptoms. This treatable condition can be life-threatening if not swiftly recognized. Therefore clinicians should have low index of suspicion to test for VZV meningoencephalitis to prevent morbidity and mortality.