Relapsing herpes simplex encephalitis following antiviral therapy

HSV encephalitis-induced anti-NMDAR encephalitis in a 67-year-old woman: report of a case and review of the literature

Herpes simplex virus (HSV) encephalitis can induce an autoimmune encephalitis mediated by autoantibodies against the N-methyl-D-aspartate receptor (NMDAR). Post-HSV NMDAR encephalitis and de novo NMDAR encephalitis have been more commonly described in children and young adults. We describe the case of a 67-year-old woman with post-HSV NMDAR encephalitis and review the relevant literature. Clinical, serological, neurophysiological, and imaging evaluations were undertaken in the evaluation of this patient. A literature review was performed. Nearly 2 months after a typical course of HSV encephalitis confirmed by HSV polymerase chain reaction studies from the spinal fluid and treated with intravenous acyclovir, a 67-year-old woman suffered neurological deterioration. There was no evidence of active HSV infection, but NMDAR antibodies were found in her serum and spinal fluid. The patient improved after initiation of immunosuppressive therapy. All patients who experience new or recurrent neurological symptoms following recovery from HSV encephalitis should be evaluated for post-infectious autoimmune encephalitis, including NMDAR encephalitis.

Clinical Neuropathology practice guide 4-2013: post-herpes simplex encephalitis: N-methyl-Daspartate receptor antibodies are part of the problem

Classic herpes simplex virus encephalitis (HSVE) is an acute viral infection that usually follows a monophasic disease course; however some patients, mainly children, experience a relapse within weeks or months after the initial event. In a subset of these patients a viral reactivation is unlikely because the CSF PCR for HSV is negative, repeated MRI does not show new necrotic lesions, and the symptoms are refractory to antiviral therapy. These patients often develop choreoathetosis variably accompanied by behavioral changes and seizures, and a postinfectious immune-mechanism has been postulated. Recent studies demonstrated that 7% of patients with HSVE harbor NR1 N-methyl-D-aspartate receptor (NMDAR) IgG antibodies. Moreover, a child with post-HSVE choreoathetosis was found to have NMDAR antibodies; the patient did not improve with antiviral therapy but recovered after aggressive immunotherapy. Based on these findings, evidence is increasing that a subgroup of post-HSVE represents a separate disease entity, which in fact is anti-NMDAR encephalitis. Patients with relapsing HSVE or prolonged atypical symptoms, who have negative CSF PCR for HSV should routinely be tested for NMDAR IgG antibodies in CSF and serum. It is important to be aware of this differential diagnosis because patients respond to immunotherapy.

MRI deterioration in herpes simplex encephalitis despite clinical recovery

OBJECTIVES

Herpes simplex virus type 1 is a sporadic cause of viral encephalitis. Relapse of encephalitis occurs in up to 10% of patients, manifested by recurrent symptoms, clinical and MRI findings, and the presence of herpes simplex virus type 1 DNA in the cerebrospinal fluid (CSF).

METHODS

We describe the clinical features, MRI findings and outcome in 2 patients with herpes simplex encephalitis during the acute phase and 6 months after the onset of encephalitis.

RESULTS

Both patients had a good response to treatment and an excellent recovery. Despite clinical recovery, in a 6-month follow-up MRI lesions consistent with recurrence were disclosed, without any clinical findings or CSF abnormalities.

CONCLUSIONS

The mechanism underlying this MRI deterioration is unclear and an immune-mediated mechanism may be involved. Thus, MRI deterioration after herpes simplex encephalitis should be interpreted with caution and it does not always represent a relapse, especially when the imaging studies do not correlate with the clinical and CSF findings.

Predictors of a prolonged clinical course in adult patients with herpes simplex virus encephalitis

OBJECTIVE

Herpes simplex virus encephalitis (HSVE) patients occasionally follow a prolonged course despite standard antiviral treatment. The purpose of this study was to analyze clinical variables to identify predictors of a prolonged course.

METHODS

A series of 23 HSVE patients treated with acyclovir (ACV) during the acute stage were selected and divided into 2 groups: the non-prolonged group (n = 15), with improvement within 2 weeks after initial ACV treatment; and the prolonged group (n = 8), without improvement within 2 weeks. Differences in clinical variables, including age, duration from onset to initial ACV treatment, Glasgow coma scale (GCS) score, corticosteroid administration, detection of abnormal lesions on initial cranial computed tomography (CT) and magnetic resonance imaging, detection of periodic lateralized epileptiform discharges on electroencephalogram, and clinical outcome, were compared between the groups.

RESULTS

There were significant differences in GCS score, clinical outcome, and detection of lesions on CT between the non-prolonged and prolonged groups [p = 0.021, p = 0.041 (Mann-Whitney's U test), respectively, and p = 0.027 (Fisher's exact test)]. Four of the eight patients with a prolonged course had a poor outcome despite treatment with additional drugs.

CONCLUSION

A lower GCS and a higher rate of lesions on CT were identified as predictors of a prolonged course for HSVE. These predictors are in accordance with the conventional predictors of poor outcome for HSVE. This study suggests that the initial ACV treatment was insufficient for HSVE patients with these predictors at the acute stage. The initial treatment may need to be modified for such patients.

Human herpes simplex virus infections: epidemiology, pathogenesis, symptomatology, diagnosis, and management

Eight of the more than 80 known herpesviruses are human pathogens. Human herpes simplex virus (HSV) is a contagious infection with a large reservoir in the general population. It has a potential for significant complications in the immunocompromised host. In addition, psychological distress caused by the negative stigma associated with genital herpes and visible facial lesions in those experiencing frequent outbreaks renders it a challenging clinical dilemma. This article reviews the epidemiology, pathogenesis, and diagnostic features of HSV infections, providing the clinician with an up-to-date understanding of the available management strategies for mucocutaneous HSV-induced disease.

Postencephalitic chronic granulomatous disease

This report details the evolution of a case of herpes simplex encephalitis to chronic granuloma in a 13-year old female who, at the age of 8, suffered herpes simplex virus type 1 encephalitis. Eight months later, she developed an intracranial hypertension syndrome with the onset of a new lesion in the necrosed zone of her right temporal lobe, with no viral presence in the cerebrospinal fluid. The histologic characteristics were those of chronic granuloma with multinucleated giant cells and calcifications. Initially treated for neurosarcoidosis, the patient remained steroid-dependent for 4 years and the steroids could only be withdrawn by treatment with Infliximab. This type of evolutive pattern has probably been completely overlooked until now; it can only be accurately diagnosed by biopsy. It was initially mistaken for neurosarcoidosis.

Herpes simplex encephalitis: adolescents and adults

Herpes simplex encephalitis (HSE) remains one of the most devastating infections of the central nervous system despite available antiviral therapy. Children and adolescents account for approximately one third of all cases of HSE. Clinical diagnosis is suggested in the encephalopathic, febrile patient with focal neurologic signs. However, these clinical findings are not pathognomonic because numerous other diseases in the central nervous system can mimic HSE. Neurodiagnostic evaluation can provide support for the diagnosis by the demonstration of temporal lobe edema/hemorrhage by magnetic resonance image scan and spike and slow-wave activity on electroencephalogram. In the current era, the diagnostic gold standard is the detection of herpes simplex virus (HSV) DNA in the cerebrospinal fluid by polymerase chain reaction (PCR). Although PCR is an excellent test and preferable to brain biopsy, false negatives can occur early after disease onset. Acyclovir is the treatment of choice and is administered at 10 mg/kg every 8 h for 21 days. Even with early administration of therapy after the disease onset, nearly two thirds of survivors have significant residual neurologic deficits. Current investigative efforts are assessing the prognostic value of quantitative PCR detection of viral DNA at the onset of therapy as well as at the completion of therapy and the contribution of prolonged antiviral therapy to improved neurologic outcome.

Incidence and pathogenesis of clinical relapse after herpes simplex encephalitis in adults

OBJECTIVES

To study the occurrence of relapse of herpes simplex encephalitis (HSE) and to find out whether soluble activity markers in cerebrospinal fluid (CSF) indicate direct viral or immune- mediated events.

METHODS

A consecutive series of 32 adult survivors of HSE were followed to determine the incidence of clinical relapse of HSE. Four patients had neurological deterioration interpreted as relapsing HSE. Four non-relapsing HSE cases were selected as matched controls. Fifty nine batched, paired CSF and serum samples from the eight HSE patients were analysed for soluble activity markers, predominantly cytokines and mediators (interferon-gamma, soluble CD8, tumour necrosis factor-alpha, and interleukin-10), amount of HSV-DNA and markers of glial and neuronal destruction (neurofilament protein, glial fibrillary acidic protein, S-100-beta, and neuron specific enolase).

RESULTS

Relapse of HSE was diagnosed in 3 of 26 (12 %) acyclovir-treated patients (5 episodes during 6.1 years of followup) and in 1 of 6 vidarabine-recipients. All relapses occurred from 1 to 4 months after acute HSE, except for a second relapse after 3.3 years in one patient. Computer tomography at relapses revealed few abnormalities apart from those found during the primary disease. Intravenous acyclovir and corticosteroids were given for 7-21 days in all the relapse patients. All relapse patients seemed to recover to the pre-relapse condition. HSV-DNA was demonstrated in CSF in all patients during the acute stage but not in any of 13 CSF samples taken during relapse phases. The HSV viral load during the acute stage of HSE was not higher or of longer duration in the relapsing patients than in the non-relapsing HSE controls. The levels of sCD8 were increased in nearly all CSF samples tested with peaks of sCD8 at one month of acute HSE. In all episodes of relapse, sCD8 peaks were detected during the first week at high levels. CSF levels of neuron-specific enolase, S-100 and glial fibrillary acidic protein were markedly lower at relapse than at the acute stage of HSV-1 encephalitis.

CONCLUSION

The lack of demonstrable HSV DNA in CSF, the lack of acute CSF signs and the lack of signs of neural and glia cells destruction indicate that a direct viral cytotoxicity is not the major pathogenic mechanism in relapse. Instead, the pronounced CSF proinflammatory immunological response and the relative lack of CSF anti-inflammatory cytokine IL-10 response suggest immunologically-mediated pathogenicity.

Herpes simplex: Encephalitis children and adolescents

Herpes simplex encephalitis (HSE) remains one of the most devastating infections of the central nervous system despite available antiviral therapy. Children and adolescents account for approximately one third of all cases of HSE. Clinical diagnosis is suggested in the encephalopathic, febrile patient with focal neurologic signs. However, these clinical findings are not pathognomonic because numerous other infections in the central nervous system can mimic HSE. Support for the diagnosis from a neurodiagnostic perspective is aided by the demonstration of disease of the temporal lobe by magnetic resonance image scan and spike and slow-wave activity on electroencephalogram. In the current era, the gold standard for establishing diagnosis is the detection of herpes simplex virus DNA in the cerebrospinal fluid by polymerase chain reaction (PCR). Although PCR is an excellent test and far more desirable than brain biopsy, false negatives can occur early after disease onset. Current therapeutic management calls for the administration of acyclovir at 10 mg/kg every 8 hours for 21 days. Even with early administration of therapy after the onset of disease, nearly two thirds of survivors will have significant residual neurologic deficits. Recent investigative efforts are assessing the value of PCR detection of viral DNA at the completion of therapy and the value of prolonged antiviral therapy.

Productive herpes simplex virus in brain of elderly normal subjects and Alzheimer's disease patients

It was previously shown that herpes simplex virus type 1 (HSV1) DNA resides latently in a high proportion of aged brains and that in carriers of the type 4 allele of the apolipoprotein E gene (APOE-epsilon4), it confers a strong risk of Alzheimer's disease. It was suggested that initial entry of brain by HSV1 and any subsequent reactivation(s) would cause a type of limited encephalitis, the resulting damage being more harmful in APOE-epsilon4 carriers. Reactivation(s) would induce synthesis of intrathecal antibodies; these are long-lived after herpes simplex encephalitis so they were sought in cerebrospinal fluid (CSF) of Alzheimer's disease patients and age-matched normal subjects. Intrathecal antibodies to human herpesvirus 6 (HHV6) were also sought as DNA of this virus has been detected previously in a high proportion of Alzheimer's disease brains. Antibody indices for HSV and HHV6 were measured using indirect ELISA for IgG antibody, and single radial immunodiffusion was used for albumin, in serum and CSF. A raised antibody index (>1.5) indicative of virus-specific intrathecal HSV1 IgG synthesis was found in 14/27 (52%) Alzheimer's disease patients and 9/13 (69%) age-matched normals (difference non-significant). A raised antibody index to HHV6 was detected in 22% of the Alzheimer's disease patients and in no normals, so presumably this virus either did not reactivate in brain or it elicited only short-lived intrathecal antibodies. The HSV1 results confirm the original PCR findings that show the presence of HSV1 DNA sequences in many elderly brains, and indicate also that the whole functional HSV1 genome is present, and that the virus has replicated.

Clinical manifestations and treatment considerations of herpes simplex virus infection

Herpes simplex viruses (HSV) types 1 and 2 cause infections manifesting as dermatologic, immunologic, and neurologic disorders. Some of the most important manifestations and complications of HSV infection are considered here in a neuroanatomic context. This discussion should aid in understanding the pathogenesis and, in some cases, diagnosis and management of associated HSV-related diseases. The sensory nervous system, rather than skin and mucous membranes, is the primary target of HSV infection. With the intention of extending the benefits of acyclovir, valacyclovir is now being explored in a number of HSV-related conditions. This review extends contemporary thinking about how new antiherpetic drugs might be put to greater therapeutic use in the future.

Intravenous infusion of cereport increases uptake and efficacy of acyclovir in herpes simplex virus-infected rat brains

The outcome of herpes simplex virus (HSV) infections manifesting as encephalitis in healthy or immunocompromised individuals is generally very poor with mortality rates of about 8 to 28% with treatment. The long-term prognosis of survivors is often problematic, posing the need for alternative treatments that may decrease the mortality and morbidity associated with herpes encephalitis. This study addresses one such approach that includes a temporary permeabilization of the blood-brain barrier during treatment with acyclovir (ACV). In these studies we utilized a synthetic bradykinin analog, Cereport (RMP-7), in conjunction with ACV to treat HSV infection of the brain in a rat model. Cereport, infused intravenously via the jugular vein, was shown to increase [(14)C]ACV uptake in both the HSV-1-infected and -uninfected rat brain by approximately two- to threefold, correlating with enhanced efficacy of ACV in various brain compartments. In another series of experiments to determine efficacy, various doses of unlabeled ACV were administered during infusion with RMP-7. The decrease in viral titers in the temporal regions of the brain after 5 days of treatment suggested that this approach enhanced the efficacy of ACV treatment. These data indicated that Cereport infused with ACV enhances both the penetration and efficacy of this drug in the treatment of an experimental HSV-1 infection of the rat brain.

Diaschisis in chronic viral encephalitis with Koshevnikov syndrome

The authors report a 61-year-old man with chronic viral encephalitis and Koshevnikov syndrome occurring 42 months after initial symptom of right hemiparesis. Serial computed tomography of the brain showed changes in the attenuation of the left temporal lobe lesion over time. Magnetic resonance images of the brain showed enlargement of left temporoparietooccipital lobes with cortical gyral enhancement on T1-weighted images following intravenous administration of gadolinium-DTPA. 99mTc-HMPAO single-photon emission computerized tomography showed increased radioactivity and hyperperfusion in the left temporoparietal region with paradoxically decreased local tissue perfusion at the contralateral right hemisphere. Follow-up magnetic resonance images of the brain 4 years later showed atrophy of bilateral cerebral hemispheres. We postulate that a "transcallosal diaschisis" with subsequent degeneration is a possible mechanism. A brain biopsy from the left temporal lobe lesion showed pictures compatible with viral encephalitis probably herpes simplex encephalitis.

Advantage of polymerase chain reaction in the diagnosis of herpes simplex encephalitis: presentation of 5 atypical cases

Four case of herpes encephalitis (HSVE) are described. The diagnosis was established by polymerase chain reaction (PCR) assay of cerebrospinal fluid (CSF). These reports illustrate different situations in the clinical management of this disease. PCR was considered useful in confirming the HSVE diagnosis in 3 atypical cases, and in the differentiation between virologic failure and postinfectious encephalitis in a patient with recurrence of symptoms. A case with typical HSVE clinical findings is also reported where PCR was negative and a temporal lobe lymphoma was diagnosed at autopsy. This last case is representative of the utility of PCR in the management of other diseases mimicking HSVE.

Twenty-five coregulated transcripts define a sterigmatocystin gene cluster in Aspergillus nidulans

Sterigmatocystin (ST) and the aflatoxins (AFs), related fungal secondary metabolites, are among the most toxic, mutagenic, and carcinogenic natural products known. The ST biosynthetic pathway in Aspergillus nidulans is estimated to involve at least 15 enzymatic activities, while certain Aspergillus parasiticus, Aspergillus flavus, and Aspergillus nomius strains contain additional activities that convert ST to AF. We have characterized a 60-kb region in the A. nidulans genome and find it contains many, if not all, of the genes needed for ST biosynthesis. This region includes verA, a structural gene previously shown to be required for ST biosynthesis, and 24 additional closely spaced transcripts ranging in size from 0.6 to 7.2 kb that are coordinately induced only under ST-producing conditions. Each end of this gene cluster is demarcated by transcripts that are expressed under both ST-inducing and non-ST-inducing conditions. Deduced polypeptide sequences of regions within this cluster had a high percentage of identity with enzymes that have activities predicted for ST/AF biosynthesis, including a polyketide synthase, a fatty acid synthase (alpha and beta subunits), five monooxygenases, four dehydrogenases, an esterase, an 0-methyltransferase, a reductase, an oxidase, and a zinc cluster DNA binding protein. A revised system for naming the genes of the ST pathway is presented.

Polymerase chain reaction in the investigation of "relapse" following herpes simplex encephalitis

Five cases of apparent relapse of herpes encephalitis were investigated. All patients recovered after antiviral and corticosteroid therapy. Samples of CSF taken from the patients at intervals through the initial and subsequent encephalitic episode were examined. PCR amplification of a 351 bp sequence from the Herpesvirus simplex (HSV) thymidine kinase gene demonstrated the presence of HSV DNA in CSF taken during the initial encephalitic illness but not during the second encephalitic episode. Intrathecal synthesis of HSV antibody (HSV antibody index > 1.9) was observed in all cases following the first episode, and there appeared to be no significant increase in intrathecal antibody synthesis in the second episode. High levels of CSF myelin basic protein were found during the acute phases of both the initial and the subsequent encephalitic illnesses. These data suggest that at least in our series of five patients, relapse following HSE may not be due to active viral replication.

Choreoathetosis as an initial sign of relapsing of herpes simplex encephalitis

Twelve children with type 1 herpes simplex encephalitis (3 with relapse, 9 without) have been monitored during the past 7 years. Ten of the children received intravenous infusion of acyclovir (30 mg/kg/day) for 10 days, 1 child who experienced relapse received 15 mg/kg/day, and another relapsed child received no antiviral agents until relapse. Relapse occurred 20-36 days after initial onset. All relapsed patients underwent another 10 days of acyclovir treatment (30 mg/kg/day). Choreoathetosis appeared as the initial sign of relapse followed by rapidly progressive unresponsiveness in all 3 relapsed patients: in 1 nonrelapsed patient choreoathetosis occurred during the recovery period. In these 4 patients involuntary movement was remitted within 3 months to 2 years. One patient with choreoathetosis died of measles pneumonia 4 months after onset of herpes simplex encephalitis and the surviving 3 were severely retarded. Although neuroimaging sparing of basal ganglia does not indicate structural and functional abnormalities, the disturbance of the neural connection among the basal ganglia and the cerebral cortex, which manifested severe damage over frontal, temporal, and parietal mantles on CT, may be the source of movement disorders in these patients. We conclude that choreoathetosis may be the first sign of relapse of herpes simplex encephalitis in children and may be an indicator of poor prognosis. The neuropathogenesis of choreoathetosis requires further investigation.

Distribution of herpes simplex virus DNA in the brains of human long-term survivors of encephalitis

We have examined the distribution of type 1 herpes simplex virus (HSV-1) DNA in the brains of 8 humans surviving for between 4 months and 17 years after acute encephalitis. Histological examination showed neuronal loss and gliosis largely confined to the temporal and frontal lobes, typical of HSV-1 encephalitis. There was a widespread persistent inflammatory infiltrate, present in both the cerebrum and brainstem. Viral DNA was detected in paraffin sections of formalin-fixed paraffin-embedded autopsy brain by use of the polymerase chain reaction to amplify a fragment of the HSV-1 thymidine kinase gene. HSV-1 DNA was amplified from the cerebrum in 6/8 cases and from the brainstem in 4/8 cases. These findings suggest the possibility that HSV-1 may persist within the human central nervous system after acute herpes simplex encephalitis. The distribution of the viral DNA correlates better with that of the persistent inflammatory infiltrate than with the destructive lesions of the acute encephalitis.

Chorea as a presentation of herpes simplex encephalitis relapse

Three infants, ages 3 months to 3 years, presented with chorea as the initial manifestation of herpes simplex encephalitis (HSE) relapse. Patient 2, treated with repeated 10 day courses of 30 mg/kg/day of acyclovir, had no clear improvement in neurological status. Patient 1, treated with a repeated 10-day course, improved only to have another HSE relapse 4 years later. Patient 3 clearly improved soon after a 3-week course of acyclovir at conventional dosages. A fourth patient (Patient 4) who relapsed with chorea after what was thought to be HSE, and who did not respond to repeated acyclovir treatment, was negative for herpes simplex virus indicators on brain biopsy and DNA testing. We recommend treating all patients suffering from HSE with a minimum 3-week course of acyclovir at 30-35 mg/kg/day in 3 divided doses.

Herpes simplex encephalitis with relapse

Three children are described in whom herpes simplex encephalitis (HSE) followed a clearly biphasic course. The secondary deterioration may be due to a resurgence of the viral infection and calls into question the adequacy of current treatment regimens for HSE. Alternatively, a postinfectious neuroallergic process may be active in which case immunomodulatory treatment might be more appropriate than further antiviral treatment.

Retropharyngeal abscess

Of 31 children with retropharyngeal abscess treated at this hospital between 1954 and 1990, 17 (55%) were 12 months old or less and 10 (32%) less than 6 months. Three of these 10 children were neonates, only one of whom had a predisposing congenital lesion. Fourteen children (45%) had a preceding upper respiratory illness and four (13%) had a prior history of pharyngeal trauma or ingestion of a foreign body. In children less than 1 year old the clinical presentation was usually classical with fever, neck swelling, stridor, and pharyngeal swelling. Significantly fewer children over 1 year had neck swelling and no child over 3 years old had stridor. A lateral radiograph of the neck, when performed, had a sensitivity of 88% in diagnosis. Bacteria isolated included pure growths of Staphylococcus aureus (25%), klebsiella species (13%), group A streptococcus (8%), and a mixture of Gram negative and anaerobic organisms (38%). There were two deaths. In six cases (24%) the abscess recurred necessitating further surgical drainage.

Autopsy neuropathological findings in 'burnt out' herpes simplex encephalitis and use of the polymerase chain reaction to detect viral DNA

We have conducted an autopsy study of the brains of three patients with 'burnt out' temporal and frontal lobe encephalitis, thought to be due to previous herpes simplex virus infection. The brains showed marked atrophy and yellow-brown discolouration predominantly involving the anterior part of both temporal lobes. Histology revealed destruction of grey and white matter, perivascular and leptomeningeal aggregates of lymphocytes and macrophages, and severe gliosis. Immunohistochemistry for herpesvirus antigens was negative but, by use of the polymerase chain reaction, a segment of the thymidine kinase gene of herpes simplex virus type 1 was detected in sections of temporal lobe from all three brains. These findings support the hypothesis that herpes simplex virus may persist within the central nervous system after acute herpes encephalitis, to cause latent or low-grade productive infection.

Herpes simplex virus infections of the central nervous system. Encephalitis and neonatal herpes

Herpes simplex virus (HSV) infections are among the most commonly encountered in humans. Fortunately, the resulting diseases are more usually nuisances, such as recurrent fever blisters, rather than life threatening or morbidity inducing. Nevertheless, HSV can result in disease of the central nervous system (CNS) with attendant neurological complications. Examples of the latter include herpes simplex encephalitis (HSE) or neonatal HSV infection. The past decade has witnessed significant advances in our understanding of the pathogenesis of these 2 forms of disease and, even more importantly, their amenability to treatment. This review summarises our current understanding of the natural history, pathogenesis, presentation, and treatment of HSV infections of the CNS. Because of the life-threatening nature of herpes simplex infections of the CNS, particular attention is paid to clinical presentation and differential diagnosis of confounding entities which mimic herpes simplex encephalitis. The controversy of brain biopsy versus alternative noninvasive diagnostic procedures is discussed. Clinical presentation and, importantly, the lack of uniform clinical presentation, as well as the value of intervention with appropriate antiviral drugs such as aciclovir and vidarabine (adenine arabinoside, ara-A), are stressed. The clinical outcome of herpes simplex virus infections of the CNS with therapy is particularly relevant. In spite of early intervention with selective and specific inhibitors of viral replication, return to normal function is not always achieved. At the conclusion of this review, the reader should be aware of the potential value of therapy as well as the problems encountered with diagnosis and management of patients with herpes simplex virus infections of the CNS.

Movement disorder following herpes simplex encephalitis

Two children, an eight-year-old girl and a seven-month-old boy, recovered from herpes simplex encephalitis with minimal neurological residua following acyclovir treatment. Subsequently, they experienced marked deterioration, interpreted as either recrudescent infection or a post-infectious phenomenon. Features of the deterioration included encephalopathy and hyperkinetic movement disorder. MRI studies showed extensive neocortical damage, without involvement of the basal ganglia, thalamus or subthalamic nuclei. With aggressive supportive care, both children made a slow, steady recovery over several months. This supportive care is best provided in a closely supervised interdisciplinary setting.

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.

Acyclovir treatment of herpes simplex encephalitis: experience in a district hospital

Herpes simplex encephalitis may be underdiagnosed in Britain. We report eight patients treated at one hospital over three years. Fever, impaired consciousness or focal neurological signs were seen in all patients at presentation but herpes simplex encephalitis was rarely considered as the initial diagnosis. The electroencephalogram was the only initial investigation that was abnormal in each case and was the most useful test in establishing a clinical diagnosis. The diagnosis was confirmed by laboratory methods in each case. Following acyclovir treatment five patients were able to resume normal activities, one patient has moderate disability and two patients died. Three patients showed clinical evidence of relapse but two improved after further treatment with acyclovir. Herpes simplex encephalitis is a treatable condition and should be considered in all patients presenting with fever and neurological signs. The electroencephalogram is usually abnormal and the changes may be characteristic of the condition.

Vidarabine versus acyclovir therapy in herpes simplex encephalitis

We randomly assigned 208 patients who underwent brain biopsy for presumptive herpes simplex encephalitis to receive either vidarabine (15 mg per kilogram of body weight per day) or acyclovir (30 mg per kilogram per day) for 10 days. Sixty-nine patients (33 percent) had biopsy-proved disease; 37 received vidarabine, and 32 acyclovir. The mortality in the vidarabine recipients was 54 percent, as compared with 28 percent in the acyclovir recipients (P = 0.008). Six-month mortality varied according to the Glasgow coma score at the onset of therapy. For scores of greater than 10, 7 to 10, and less than or equal to 6, mortality was 42, 46, and 67 percent in the patients treated with vidarabine, as compared with 0, 25, and 25 percent in those treated with acyclovir. A six-month morbidity assessment using an adapted scoring system revealed that 5 of 37 patients receiving vidarabine (14 percent) as compared with 12 of 32 receiving acyclovir (38 percent) were functioning normally (P = 0.021). Eight vidarabine-treated patients (22 percent) and three acyclovir-treated patients (9 percent) had moderate debility. Patients under 30 years of age and with a Glasgow coma score above 10 had the best outcome with acyclovir treatment. We conclude that acyclovir is currently the treatment of choice for biopsy-proved herpes simplex encephalitis.

Viral infections of the nervous system

Neurotropic viruses cause a number of important infectious syndromes including encephalitis, myelitis, meningitis, and radiculopathy. In this review, the biology of conventional and unconventional viruses is examined. The host immune response to viruses is discussed, and patterns of viral pathogenesis are explained. The clinical features, laboratory findings, management of important viral infections, such as herpes simplex encephalitis and epidemic encephalitis, are presented. Post-infection syndromes, such as the Guillain-Barré syndrome, and chronic viral infections, such as those causing progressive multifocal leukoencephalopathy and subacute sclerosing panencephalitis, are discussed. Current knowledge concerning the nature of unconventional virus-like agents of the spongiform encephalopathies, including kuru and Creutzfeldt-Jakob disease, is summarized. Finally, viral infections of immunocompromised patients and the possible role of viruses in the newly described acquired immunodeficiency syndrome (AIDS) are examined.

Relapse of herpes simplex encephalitis after acyclovir therapy

Acyclovir is a new and well tolerated anti-viral agent whose role in the treatment of herpes simplex encephalitis (HSE) is still being evaluated. Although relapse of adenosine arabinoside treated HSE has been documented, this paper describes the recurrence of encephalitis after treatment with the recommended course of Acyclovir. A more extended course of Acyclovir produced a rapid and sustained improvement with minimal residual neurological deficit. We emphasise the need for more prolonged treatment and an awareness of the possibility of relapse when using Acyclovir for HSE.