The Role of Continuous Electroencephalography in Childhood Encephalitis

Abstract

Background

Seizures are a known complication of encephalitis. We sought to determine the incidence of seizures and the relative utility of routine and continuous electroencephalography in children with suspected encephalitis.

Methods

Records from all 217 children (ages 0-20 years, enrolled 2004-2011) from our institution who had diagnostic samples sent to the California Encephalitis Project were reviewed.

Results

One hundred children (46%) had at least one seizure observed clinically or recorded on electroencephalography. Diffuse abnormalities (e.g., generalized slowing) were more common than focal or epileptiform abnormalities (88.9% vs 63.2% and 57.3%, respectively; P < 0.0001), but focal and epileptiform abnormalities were more correlated with seizures (91.0% [P = 0.04] and 89.2% [P = 0.05], respectively vs 76.9%). Fifty-four patients (25%) had at least 1 day of continuous electroencephalography. When used, continuous electroencephalography recorded a seizure in more than half of patients. Six children had no recognized seizure (clinical or electrographic) before continuous electroencephalography was performed. Twenty-two children (10%) had a seizure recorded by continuous electroencephalography after routine electroencephalography did not record a seizure. Overall, continuous electroencephalography was more likely to capture a seizure, capture a subclinical seizure, or rule out a concerning event as a seizure than routine electroencephalography (all comparisons P < 0.0001).

Conclusions

Children with suspected encephalitis are at high risk for seizures. Continuous electroencephalography is better able than routine electroencephalography to determine whether seizures are present. Further, continuous electroencephalography can guide treatment by classifying a clinical event as seizure or seizure-mimic. Our findings support the expanded use of continuous electroencephalography in children with suspected encephalitis.

Introduction

Encephalitis occurs in 3.5-7.4 cases per 100,000 person-years in the general population with an incidence up to 16 times higher in children.¹ In the National Hospital Discharge Survey between 1988 and1997, encephalitis accounted for 230,000 hospital days and 1400 hospital deaths annually.² Children with encephalitis have diverse clinical presentations, with variable signs and symptoms including headache, meningismus, fever, changes in mental status such as lethargy or hallucinations, seizures, abnormal movements, or tremor, and focal neurological signs.1, 3 Children with symptoms consistent with encephalitis undergo medical management with a great deal of ambiguity as to their etiologic diagnosis, and most will never have a verifiable etiology for their illness.⁴ The California Encephalitis Project (CEP) was an attempt to identify etiologic agents and characterize the clinical course of patients with encephalitis; summaries of the infectious agents found and patient outcomes have been reported previously.3, 5, 6

Seizures, both clinical and subclinical, are common in children with encephalitis. Glaser et al.⁵ reported seizures in 42% of children in the CEP. Misra and Kalita⁷ reported that 37% of adults and 61% of children with encephalitis in a prospective hospital-based study had seizures. Dubray et al.⁶ reported that 62% of children with encephalitis had seizures, and that seizures were correlated with a prolonged illness and worse outcome. However, seizures can be difficult to recognize in patients with encephalitis and it is unclear whether routine electroencephalograph (EEG) is sufficient to rule out seizures in this population; in a study of intensive care unit (ICU) patients (adults and children) with suspected central nervous system infection receiving continuous EEG monitoring (cEEG), 33% had a seizure while on the monitor and 64% of those seizures had no clinical correlate.⁸ Several recent reports of children receiving ICU monitoring in pediatric ICUs show that critically ill children frequency have seizures, seizures are frequency subclinical, and seizures are correlated with poor outcomes.9, 10, 11, 12, 13, 14, 15

In this study, we report EEG and clinical findings from all children who presented to Rady Children's Hospital of San Diego (RCHSD) between 2004 and 2011 and had diagnostic samples sent to the CEP. Our findings suggest that cEEG is important in the diagnosis and management of children with symptoms consist with encephalitis.