EEG and clinical characteristics of neonatal parechovirus encephalitis

Rationale: Human parechoviruses (HPeVs) are single -stranded ribonucleic (RNA) viruses belonging to the picornaviridae family with characteristics similar to enteroviruses. They either cause mild respiratory and gastrointestinal or no symptoms in older children and adults but can be a major cause of central nervous system (CNS) infection in the neonatal period and demonstrate a seasonal predilection. Starting in March 2022, we saw eight patients with polymerase chain reaction (PCR) proven HPeV encephalitis with seizures and some electroencephalographic (EEG) features raising concerns for neonatal genetic epilepsy. Although cerebrospinal fluid (CSF) and imaging findings have been previously described, there is little emphasis on seizure presentation and EEG findings of HPeV in the literature. We wish to highlight the EEG and seizure semiology of HPeV encephalitis that may mimic a genetic neonatal epilepsy syndrome. Methods: Retrospective chart review of all neonates seen at Children's Health Dallas, UTSW Medical Center between 03/18/2022–06/01/2022 with HPeV encephalitis. Results: Term neonates (postmenstrual age 37–40 weeks) presented with a variable combination of fever, lethargy, irritability, poor oral intake, erythematous rash, and focal seizures. One patient with a single episode of limpness and pallor did not undergo EEG due to a low suspicion for seizures. CSF indices were normal in all patients. EEG was abnormal in all patients where performed (n = 7). EEG features included dysmaturity (7/7, 100 %); excessive discontinuity (6/7, 86 %); excessive asynchrony (6/7, 86 %); multifocal sharp transients (7/7, 100 %). Focal/multifocal seizures were captured in 6/7 (86 %); tonic in 3/7 (42 %) and described as migrating in 2 patients. Subclinical seizures were noted in 6/7 (86 %) with status epilepticus in 5/7 (71 %) patients. In 2/7 (28 %) the EEG showed a burst suppression pattern with poor state variation and voltages of < 5–10 uV/mm during the inter-burst intervals. Repeat EEG (3–11 days post initial EEG) showed improvement in 3 of 4 patients. No patient had ongoing seizures beyond day two of admission (22.5 h after EEG initiation). MRI showed extensive restricted diffusion in the supratentorial white matter, thalami, and less frequently the cortex, mimicking imaging findings of a metabolic or hypoxic-ischemic encephalopathy (7/8). Seizures responded within 36 h of presentation to treatment with acute bolus doses of medications. One patient died due to diffuse cerebral edema and status epilepticus. Six patients had a normal clinical exam at discharge. All patients started on maintenance antiseizure medication (ASM) were sent home on either a single medication or two medications (phenobarbital and levetiracetam) with plans to wean phenobarbital after discharge. Conclusions: HPeV is a rare cause of seizures and encephalopathy in neonates. Prior studies have emphasized specific patterns of white matter injury on imaging. We demonstrate that HPeV also commonly presents with clonic or tonic seizures with or without apnea and often subclinical multifocal and migrating focal seizures that could mimic a genetic neonatal epilepsy syndrome. Interictal EEG shows a dysmature background with excessive asynchrony, discontinuity, burst-suppression pattern, and multifocal sharp transients. However, we note that 100 % of patients responded quickly to standard ASM, and did not have seizures after hospital discharge- a factor that can help distinguish it from a genetic epilepsy syndrome.