Early diagnosis of herpes simplex encephalitis in childhood. Clinical, neurophysiological and neuroradiological studies

The spectrum of herpes simplex encephalitis in children

Clinical and basic science research carried out in recent years into herpes simplex encephalitis (HSE) have shown that the concept of a "classical" picture of HSE in children is now outdated and that our current knowledge of the disease is probably only the tip of an iceberg. Indeed, increasing evidence supports the existence of a wider range of pathophysiological mechanisms, clinical presentations and disease progressions in paediatric HSE. This paper reviews the clinical, biological and radiological data available and redefines the spectrum of HSE in children. Full understanding of the condition should improve the management of suspected cases and decrease the morbidity and the mortality associated with this disease.

Polymerase chain reaction-proved herpes simplex encephalitis in children

OBJECTIVE

To investigate the clinical features in PCR-proved herpes simplex encephalitis (HSE) in children, excluding neonates.

METHODS

We studied the clinical manifestations and laboratory findings of 24 children in whom the diagnosis of herpes infection was confirmed by the PCR assay and compared them with those of 38 children with central nervous system infections other than HSE.

RESULTS

There were no significant differences between groups in the percentage with fever or convulsions, the initial neurologic symptoms or the level of consciousness. Analysis of cerebrospinal fluid showed no significant differences in the cell count or concentration of protein and glucose. Computerized tomography of the brain identified localized abnormalities in 18 (75%) of the 24 HSE patients and in 10 (31%) of the 32 non-HSE patients (P = 0.001). Periodic lateralized epileptiform discharges, abnormal findings on electroencephalography, were detected in 8 (36%) of 22 HSE patients and in none of the non-HSE patients (P = 0.0001). The rates of moderate to severe morbidity and death were significantly higher in the HSE patients than in the non-HSE patients. Of the 9 HSE patients with a Glasgow Coma Scale score > or = 11, all patients recovered completely. HSE patients younger than 3 years of age were more likely to develop severe sequelae or to die of the disorder than older patients (P = 0.02).

CONCLUSIONS

There were no specific clinical characteristics of HSE patients. The results of electroencephalography and computerized tomography were helpful, but not confirmatory, in diagnosing HSE. The Glasgow Coma Scale score and age significantly influenced the mortality and morbidity in the HSE patients.

Expanded spectrum of herpes simplex encephalitis in childhood

We designed a polymerase chain reaction method to detect herpes simplex virus (HSV) DNA in spinal fluid from patients with encephalitis. The polymerase chain reaction amplified a 211 base-pair segment of the HSV DNA polymerase gene. Applying this method, we diagnosed HSV type 1 infection in three young children, aged 7 to 13 months, who had atypical forms of the illness. On the basis of magnetic resonance imaging, their disease was diffuse or multifocal in two cases and, in all three, lacked the temporal lobe involvement considered characteristic of HSV encephalitis beyond the neonatal period. Most of the diffuse or multifocal abnormalities detected by magnetic resonance imaging were not apparent by computed tomography. Restriction enzyme analysis of the polymerase chain reaction products from all three patients indicated that their disease was caused by HSV type 1. We conclude that in preschool-age children beyond the neonatal period, the spectrum of HSV encephalitis includes multifocal or diffuse involvement of the brain, which may be detected most efficiently by magnetic resonance imaging. The polymerase chain reaction method has the potential for providing an early diagnosis, but further studies are required to define the sensitivity and specificity of the polymerase chain reaction before it can be used for routine clinical decision making.

Outcome after childhood encephalitis

The prognosis for 73 children treated for encephalitis between 1973 and 1983 was evaluated. 70 children participated in a follow-up examination 2.4 to 12.9 years after the acute phase of the disease. The 61 school-aged children had lower performance and full-scale IQs than their randomly selected, age- and sex-matched controls. Visual acuity was more often reduced, and they more often had focal slowing on EEG and electronystagmogram abnormalities. Clinically, these differences were not significant. Encephalitis with a poor prognosis occurred seldom, the incidence being 3.5 cases per one million children at risk annually. These results show that the prognosis for childhood encephalitis is much better than anticipated on the basis of experience mainly with herpes simplex virus encephalitis.

Brain stem encephalitis due to herpes simplex virus

A 6 year old child is described with infection due to herpes simplex virus type 1 causing brain stem encephalitis. The diagnosis was established by enzyme immunosorbent assays of the cerebrospinal fluid and serum which demonstrated antibody responses to herpes simplex virus. Recovery occurred and the importance of early use of acyclovir in achieving a good outcome is emphasized.

Acute pseudobulbar palsy due to bilateral focal cortical damage: the opercular syndrome of Foix-Chavany-Marie

Two children are described who suddenly developed an encephalitic illness with intractable bilateral facial seizures. The seizures subsided over several days, but the children were left with the signs of pseudobulbar palsy and are unable to speak or swallow effectively. Bilateral destructive lesions in the opercular regions evolved on computed tomographic scans. Both children were treated with acyclovir relatively early in the illness, and cerebrospinal fluid and serum antibodies support the diagnosis of herpes simplex virus encephalitis.

Herpes simplex virus encephalitis in children

Herpes simplex encephalitis (HSE) is an uncommon disease, yet 25 to 30 per cent of cases involve children. The initial clinical findings are nonspecific (fever, altered mental status), but most cases evolve to demonstrate focal neurologic signs and symptoms. The CSF is abnormal in over 90 per cent of cases. The EEG, CT, and MRI will further help in detecting focal encephalitis. The clinician caring for a child with focal encephalitis should institute broad-spectrum antimicrobial therapy plus acyclovir, pending definitive diagnosis by ancillary tests or brain biopsy, which is positive for HSE 33 to 55 per cent of the time and is diagnostic for other treatable conditions 10 to 20 per cent of the time. Acyclovir is the drug of choice for HSE and substantially reduces mortality and morbidity. The management of HSE in a child requires an experienced team of specialists and laboratory support in a tertiary intensive care setting.

Herpes simplex virus encephalitis during childhood: importance of brain biopsy diagnosis

Twelve consecutive pediatric patients 1 day to 11 years of age with suspected herpes simplex virus (HSV) encephalitis underwent brain biopsy. Five were proved to have HSV encephalitis; seven had subdural empyema, malignant glioma, enteroviral encephalitis, (one each), and presumed viral encephalitis, non-HSV (four). Neither epidemiologic, clinical, nor noninvasive laboratory tests were able to help differentiate the two groups of patients. The EEG was more sensitive than the CT scan in demonstrating focal lesions in early HSV encephalitis. In patients with HSV encephalitis, the mean time from hospital admission to appropriate antiviral chemotherapy was 3 days, and the outcome of HSV encephalitis was uniformly poor. In patients with febrile encephalitis-like syndromes with CSF pleocytosis, focal neurologic signs, or other localizing test results (EEG, CT), anticipatory antiviral chemotherapy and brain biopsy are the only hope to prevent the poor outcome associated with HSV encephalitis, to exclude other treatable conditions, and to avoid multiple types of unnecessary empiric therapies.

Early diagnosis of herpes simplex virus encephalitis in childhood by the enzyme-linked immunosorbent assay

IgG antibody of cerebro-spinal fluid (CSF) and serum IgM antibody were determined by the enzyme-linked immunosorbent assay (ELISA) in 3 patients with herpes simplex virus encephalitis (HSVE). The ELISA detected the early rise of IgG antibody for herpes simplex virus (HSV) in CSF on the 3rd/4th day from onset of symptoms and IgM antibody in serum similarly on the 3rd/4th day, respectively. CSF albumin, IgG index and daily IgG synthesis during the early phase of HSVE showed significantly high levels. However, there was no significant increase of complement-fixing antibody and neutralizing antibody for HSV of serum and CSF in 2 of 3 patients. The ELISA turned out to be a more sensitive and convenient test for the early diagnosis of HSVE.

Computed tomography in young children with herpes simplex virus encephalitis

Computed tomographic (CT) scans were obtained from eight infants and young children with herpes simplex virus encephalitis. In two cases the initial scan showed diffuse edematous changes as a mass effect without laterality. Unilateral localized low attenuation in the initial scan was evident 4 days after the onset in one patient, and high attenuation in the initial scan appeared on the 6th day in another patient, but in general, it was not possible to establish an early diagnosis of herpes simplex virus encephalitis from CT scan. In the longitudinal study the calcification with ventriculomegaly appeared in 3 of 5 survivors, and gyriform calcification in 2 of 3 patients, respectively. The appearance of multicystic encephalomalacia was evident in one patient 6 months after the onset of neonatal herpes simplex encephalitis. It is shown that the CT findings of neonates and young children with herpes simplex encephalitis are different from those of older children and adults, and the importance of longitudinal CT studies was stressed in clarifying the pathophysiology of the central nervous system involvement in survivors.

EEG in neonatal herpes simplex encephalitis

The EEGs of 21 newborns with herpes simplex encephalitis were analysed. The diagnosis was based on the demonstration of herpes simplex infection in association with neurological symptoms, other etiological factors being excluded. Sixteen of 21 babies (76%) showed in their EEGs electrical seizures, either focal or unilateral. These paroxysms consisted of sharp waves or slow waves repeating at pseudo-periodic intervals, usually of 0.5-2 sec. Individual paroxysms had a duration of 10-20 sec in 6 babies and 1-2 min in 10 patients. During the same period, 20 other babies displayed the same EEG finding. Of these, 11 had encephalitis of unknown etiology. In our series there appeared to exist a correlation between both the duration of the electrical seizures and the degree of EEG background abnormality and the clinical outcome. Babies with markedly abnormal background and long-lasting paroxysms tended to have a poor prognosis. It is concluded that in newborns with clinical signs of encephalitis who show in their EEGs paroxysms of the type described, the possibility of herpes simplex encephalitis should be considered.