Acute Encephalitis

Electroencephalography for diagnosis and prognosis of acute encephalitis

OBJECTIVES

To confirm the previously identified EEG characteristics for HSV encephalitis and to determine the diagnostic and predictive value of electroencephalography (EEG) features for etiology and outcome of acute encephalitis in adults. In addition, we sought to investigate their independence from possible clinical confounders.

METHODS

This study was performed in the Intensive Care Units of two academic tertiary care centers. From 1997 to 2011, all consecutive patients with acute encephalitis who received one or more EEGs were included. Examination of the diagnostic and predictive value of EEG patterns regarding etiology, clinical conditions, and survival was performed. The main outcome measure was in-hospital death.

RESULTS

Of 103 patients with encephalitis, EEGs were performed in 76 within a median of 1 day (inter quartile range 0.5-3) after admission. Mortality was 19.7%. Higher proportions of periodic discharges (PDs) (p=0.029) and focal slowing (p=0.017) were detected in Herpes Simplex virus (HSV) encephalitis as compared to non-HSV encephalitis, while clinical characteristics did not differ. Normal EEG remained the strongest association with a low relative risk for death in multivariable analyses (RR<0.001, p<0.001) adjusting for confounders as coma, global cerebral edema and mechanical ventilation. None of the patients with a normal EEG had a GCS of 15.

CONCLUSIONS

Normal EEG predicted survival independently from possible confounders, highlighting the prognostic value of EEG in evaluating patients with encephalitis. EEG revealed higher proportions of PDs along with focal slowing in HSV encephalitis as compared to other etiologies.

SIGNIFICANCE

EEG significantly adds to clinical, diagnostic and prognostic information in patients with acute encephalitis.

Trial with human leucocyte interferon and vidarabine in herpes simplex virus encephalitis: diagnostic and therapeutic problems

A combination therapy of human interferon, vidarabine, and dexamethasone was administered to six patients with proven (Patients I-III) or presumed (Patients IV-VI) herpes simplex virus encephalitis (HSVE). Interferon combined with dexamethasone was given to one patient with presumed HSVE (Patient VII). Leucopenia and elevated serum transaminase levels appeared in all patients and a diffuse bleeding in one of them. Patients II, III and IV died, 26, 43, and 209 days after the onset of encephalitis, respectively. Patients I, V, VI, and VII were left with moderate brain damage although their physical condition was good. HSV encephalitis presents diagnostic difficulties, complementary diagnostic methods are needed, and current therapeutic trials must be considered as preliminary.

Acute encephalitis from 1967 to 1991

We studied all the adult patients with acute encephalitis, 322 in all, in the Helsinki area, Finland, during the years 1967--1991. The average incidence was 1.4/100000 adults/year. The proportion of known and suggested etiologies in 5-year periods has risen from 36 (1967--71) to 59% (1987--91). Herpes simplex virus was identified most often (16%), followed by varicella-zoster (5%), mumps (4%), and influenza A viruses (4%). In addition, 20 other agents were identified. The leading cause of encephalitis in patients aged 65 years or more was varicella-zoster virus. Eighteen patients (5.6%) died. It appears that the etiology of encephalitis changes with age and with time. It is important to establish the etiological pattern, as this assists in prompt diagnosis, which is a prerequisite for successful therapy.

Acute viral encephalitis in adults--a prospective study

We have prospectively studied 27 adult patients attending the Department of Infectious Diseases, Göteborg, Sweden, between October 1992 and October 1996 with a diagnosis of acute viral encephalitis. In addition to cerebrospinal fluid (CSF) virus isolations and antibody analyses against herpes simplex virus, cytomegalovirus, varicella zoster virus, Epstein-Barr virus (EBV), enterovirus, adenovirus, tick-borne encephalitis virus, and mycoplasma, polymerase chain reaction test (PCR) to 5 viruses from the family of human herpes viridae, and to adenovirus as well as to enterovirus were analysed in CSF. 10 patients had herpes simplex virus type-1 (HSV-1), 1 had varicella zoster virus, 1 had tick-borne encephalitis, and 2 had Influenza A infections. In 13 patients the aetiology remained unclear. Eight patients with HSV-1 encephalitis and clinical symptoms for 2-11 d before admission were PCR-positive, while 2 patients with a < or = 2 d history of disease were negative for HSV-1 DNA on admission. These 2 patients became positive for HSV-1 DNA in CSF samples taken 4 d later in 1 case and 7 d later in the other. In 4 patients with HSV-1 encephalitis, in 1 patient with Influenza A complicated by encephalitis, and in 1 patient with encephalitis of unknown origin EBV DNA was found in CSF samples during the study. The clinical significance of these findings is unclear. The study shows that HSV-1 was the most common etiological agent in patients with viral encephalitis in the Göteborg area. In spite of improved diagnostic procedures, a large proportion of patients with symptoms and laboratory findings compatible with viral encephalitis still have an unclear aetiology.

Acute encephalitis

Acute encephalitis: etiology, clinical findings and prognosis. We studied 44 patients with acute encephalitis diagnosed in a neurological university clinic during an 11-year period. An etiology was found in 11 cases (25%). In 3 the cause was herpes simplex virus; in 2 morbilli. There were single patients in which the cause was mycoplasma pneumoniae, epidemic parotitis, ornithosis, infectious mononucleosis, influenza B-virus and recent tetanus immunization. No specific etiology was found in 33 (75%). Besides fever the most frequent sign was impairment of consciousness in 39% of cases. Four patients (9%) died. Among the survivors mental and/or focal neurological deficits persisted in 22 (55%). Most frequent was dementia in 6 cases (15% of survivors). Impaired consciousness in the acute phase indicated a worse prognosis (p < 0.005).

Predictive factors of short-term neurologic outcome in children with encephalitis

When a child is admitted to the hospital with presumed encephalitis, the physician must use clinical criteria to gauge the appropriate level of hospital care and to give a preliminary assessment of outcome to the family because the etiology is unknown. This study attempted to determine which clinical factors gathered on hospital admission would be most helpful to the physician. The records of 106 children (ages 1 month to 20 years), admitted to Rainbow Babies and Childrens Hospital between 1978-1989 who had discharge diagnoses of encephalitis, were reviewed. Seventy-five met the case definition of presumed viral encephalitis, with viral etiology established in 23% of patients. Poor short-term outcome was defined as the presence of an abnormal neurologic examination at hospital discharge, and was present in 32% of patients. Focal signs on neurologic examination (odds risk: 16.30, P < .05) and abnormal neuroimaging studies (odds risk: 5.66, P < .05) were the only 2 factors present at admission that predicted a poor short-term outcome. Glasgow coma scale at admission was predictive of an abnormal neurologic examination at discharge only when profoundly depressed (6 or less); otherwise, this scale was not useful as a prognostic tool. Factors that were not correlated with adverse outcomes included age younger than 1 year, any type of seizure occurrence, status epilepticus, diffuse or focal electroencephalographic abnormalities, or abnormal cerebrospinal fluid findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Choreoathetotic movement disorder in a boy with Mycoplasma pneumoniae encephalitis

We present a case of a 10-year-old boy who presented to the emergency department with high fever, acute choreoathetosis, weakness, and dysarthria. An EEG showed generalized slowing, and serologies defined an acute case of Mycoplasma pneumoniae encephalitis. This report describes the most common presentations, therapy, and outcomes of M pneumoniae encephalitis.

Epidemiology of encephalitis in children: a 20-year survey

Four hundred five children from the Helsinki area who were 1 month to 16 years old were treated for acute encephalitis at the Children's Hospital, University of Helsinki, from January 1968 through December 1987. Encephalitis occurred most commonly in children 1 to 1.9 years of age, among whom the incidence was 16.7 per 100,000 child-years. The incidence remained quite high until the age of 10 years, and then gradually declined to 1.0 per 100,000 child-years at the age of 15 years. Since 1983, when mumps, measles, and rubella vaccination eradicated the encephalitides associated with these microbes, the major associated agents have been varicella-zoster, Mycoplasma pneumoniae, and respiratory and enteroviruses. In infants younger than 1 year of age, the major agents were enteroviruses, herpes simplex virus, and the group of "others," whereas in older children, respiratory viruses and Mycoplasma pneumoniae, as well as varicella-zoster virus, dominated. In children aged 1 to 11 months, the causal agent could not be identified in one-half of all cases, whereas in children who were at least 10 years old, the etiology remained unknown in only one-fourth of cases. Male dominance was most evident in the 4- to 9-year age group. The difference in etiology between males and females was significant (p = 0.02); mumps and varicella were more common in boys, and adenovirus and Mycoplasma pneumoniae were more common in girls. The overall male-to-female ratio was 1.4:1. Characteristic seasonal variation occurred in encephalitides associated with mumps, measles, and entero- and respiratory viruses.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of measles, mumps, rubella vaccination on pattern of encephalitis in children

462 patients (269 males, 193 females, aged from 1 month to 16 years) with encephalitis were treated at the Children's Hospital, University of Helsinki, over a 20-year period. The incidence of encephalitis was 8.3/100,000 child-years (range 19.8 in 1974 to 2.5 in 1985 and 1986). The organisms most commonly associated with encephalitis in children were mumps, measles, and varicella viruses, and Mycoplasma pneumoniae. After the start of the nationwide measles, parotitis, and rubella (MPR) vaccination programme in 1982 in Finland, encephalitides associated with these viruses seem to have totally vanished. Currently the pathogens most often associated with childhood encephalitides are varicella-zoster, M pneumoniae, and enteroviruses. 3% of the 462 patients died from their illness, and 7% became severely damaged, with the poorest outcome occurring after multiple infections, and herpes simplex virus, cytomegalovirus or M pneumoniae infections. The decline in the total number of cases of encephalitis was not accompanied by a decrease in number of patients with a poor outcome. Patients with treatable encephalitides due, for example, to M pneumoniae and herpes viruses, need prompt attention.

The prognosis and long-term course of viral encephalitis

Of 33 patients with viral encephalitis, four (three women, one man) succumbed to the disease. Of the surviving patients, 23 were followed for a median interval of 4 years after discharge. A considerable residual syndrome could be detected in two cases only. The outcome was determined by identification of causative organism (especially herpes simplex virus), initial consciousness disturbances and pleocytosis in the cerebrospinal fluid. On the other hand, the age of the patients, electroencephalographic findings and a symptomatic epilepsy played no major role. Without confirmed virus findings, immunoglobulins were as effective as the virostatic therapy regimens; with identification of causative organism, combined treatment with acyclovir and immunoglobulins was most effective.

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.

Acute viral encephalitis in children

Fifty-seven cases satisfying criteria of the diagnosis of acute viral encephalitis were studied. They were divided into two groups: Group 1 (presumed), 48 cases; Group 2 (postinfectious), nine cases. A possible association of viral aetiology was found in 26%. Viruses isolated were: influenza (3 cases), Coxsackie virus (2), adenovirus (2), mixed cytomegalovirus and adenovirus and herpes simplex viruses (1 case each). The mortality rate was 28%. Among the 41 survivors, 76% were completely normal and 24% had neurological sequelae with focal neurological deficit in 29%; personality changes in 6%; moderate mental retardation in 2%; severe mental retardation in 4%; hyperactivity in 4% and epilepsy in 4%. The best predictors to unfavourable outcome were the rapid rate of deterioration in conscious level after admission and the age of the patients.

The pathogenesis of virus-associated encephalopathies: a prospective study of immunological mechanisms

Thirty-two patients, including 29 children, presenting with acute unexplained encephalopathies were studied prospectively for evidence of virus infection, immunodeficiency, and immunologic involvement in the pathogenesis of their illnesses. Twenty-five of these patients had a clinical diagnosis of encephalitis. Twenty-two of these 25 had laboratory evidence of active virus infection, the majority with viruses usually associated with self-limiting illness outside the central nervous system. In patients with encephalitis, immune competence, as reflected by T-cell numbers and subsets in peripheral blood, in vitro interferon production, natural killer activity, and specific antiviral antibody production, was normal. Transudation of albumin into the cerebrospinal fluid (CSF), a measure of blood-brain barrier breakdown, was seen in 40% of patients. Intrathecal antibody synthesis was suggested by an elevated IgG index in 9/20 CSF/serum pairs but was confirmed by an elevated specific IgG ratio in only 3. The serum IgG1 and IgG3 subclass levels were significantly elevated at the time of the illness and remained elevated 8 months later; IgG2 and IgG4 levels were normal. IgE levels were elevated in 50% of patients. Serum levels of IgM antibodies against Escherichia coli measured 8 months after the neurological illness were also significantly higher in encephalitis patients than in age-matched healthy controls. Human myelin basic protein did not induce proliferation in peripheral blood lymphocytes in any patient. We conclude that most encephalopathies associated with viral infections are not due to an underlying generalized immunodeficiency, and probably result from an inappropriately vigorous immune response.

[Acute diffuse lymphocytic meningoencephalitis: a clinico-pathological report of a case]

A clinicopathologic case of acute diffuse lymphocytic meningoencephalitis in a 8-year-old child is reported. Clinical picture started 7 days prior to death and was characterized by fever and occipital cephalea followed by worsening of general conditions, vomiting and generalized convulsive crisis together with cardiopulmonary arrest and coma. The pathologic examination showed alterations only in the brain, namely pronounced cerebral edema and inflammatory infiltrate, predominantly lymphocytic, perivascular, particularly in the white matter, in all regions analyzed. This case is compared to the ones described in the literature and the etiopathogenesis of acute diffuse lymphocytic meningoencephalitis is discussed. The necessity of making public cases of non-bacterial acute encephalitis is emphasized, due to the fact that most of them remain with undetermined etiology.

A major role for viruses in acute childhood encephalopathy

29 children and 3 adults with acute depression of conscious level or acute onset of focal neurological signs were studied prospectively. 3 were found to have a non-infectious cause for their illness. The presence of interferon or specific antibodies in the serum and/or cerebrospinal fluid provided evidence of active virus infection in 25 of the remaining 29 patients. There was laboratory evidence that a virus had invaded the central nervous system in 11 patients. Early investigation gave the highest diagnostic yield. Since several common viruses were identified, it appears that the nature of the illness is due more to the host response than to the nature of the infective agent.

Acute viral encephalitis

Clinical manifestations of acute viral encephalitis are described, differential diagnoses are outlined, and a diagnostic approach is recommended. Encephalitic syndromes caused by arboviruses, herpesviruses, enteroviruses, and parainfectious processes are discussed.

Encephalitis and aseptic meningitis, Olmsted County, Minnesota, 1950-1981: I. Epidemiology

All cases fulfilling stated criteria for encephalitis and aseptic meningitis in Olmsted County, Minnesota, for the period 1950 through 1981 were identified. This is, to our knowledge, the first such incidence and trend study in a delineated population, providing rates per 100,000 person-years of 7.4 for encephalitis (189 cases) and 10.9 for aseptic meningitis (283 cases). These are about twelve and six times higher, respectively, than the rates reported by the Centers for Disease Control. The rates have been stable over successive 5- or 10-year periods except for a recent increase in aseptic meningitis. Both conditions were more common in the summer months, in childhood, and among males. Viral identification using conventional laboratory tests has improved with time; in the period 1970 through 1981, virus type was specified in about one-fourth of the cases. The most common agents identified were California and mumps viruses in encephalitis, and entero and mumps viruses in aseptic meningitis. Antecedent and/or concurrent infections were noted in 42 and 35% of encephalitis and aseptic meningitis cases, respectively. No case due to mumps, measles, or rubella viruses has occurred since 1972, reflecting the impact of immunizations. Recovery was reported at the end of the acute phase in 95% of patients with aseptic meningitis, and there were no deaths. Seventy-eight percent of encephalitis patients recovered completely; the case fatality rate was 3.8%. Of the encephalitis cases, 2% were diagnosed initially postmortem.

Clinical appearance and outcome in mumps encephalitis in children

Forty-one patients with mumps encephalitis examined at the Department of Paediatrics, University of Helsinki, during the period Jan. 1, 1968, to Dec. 31, 1980, were reviewed with special reference to clinical appearance and outcome. The ratio of males to females was 4:1 and the age range 1.2 to 13.7 years. The clinical findings were high fever greater than or equal to 39 degrees C in 83.0%), impairment of locomotion and balance (36.6%), seizures (24.4%), psychic disorders (22.0%), depressed level of consciousness (19.5%), vertigo (12.9%) and/or gastric pains (12.9%). One patient with congenital toxoplasma and cytomegalovirus infections died. On leaving the hospital eight were still ataxic, one of these was not able to speak and two had difficulties in concentration. One patient was transferred to another hospital because of psychosis. At the follow-up examination 4 to 24 months after the onset of the disease two patients were ataxic and seven suffered from behavioural disturbances. Electroencephalography (12.2% of all and 25% of examined patients) showed generalized slow wave disturbance at follow-up in six patients and borderline disturbances in eight.

The incidence and aetiology of central nervous system infections in Helsinki in 1980

The aetiology of central nervous system infections was surveyed in a study at Aurora Hospital, Helsinki, in 1980. Of the 146 patients with central nervous system infections, 113 had aseptic meningitis, 23 bacterial and one tuberculous meningitis, and nine meningoencephalitis or encephalitis. The probable aetiology of aseptic meningitis was established in 67% of the 106 patients properly tested, the commonest agents being mumps (27%), Coxsackie (24%) and ECHO (9%) viruses. Haemophilus influenza type b was the most frequent cause of bacterial meningitis (39%), occurring solely among infants and young children. There were no cases due to Neisseria meningitidis group A, which used earlier to be epidemic in Finland. The incidences of aseptic, bacterial and tuberculous meningitis in Helsinki in 1980 (based on a total of 174 patients treated in the three hospitals admitting patients with central nervous system infections) were 26.7, 5.2 and 0.2 cases per 100,100 annually, and those of encephalitides and myelitis 3.5 and 0.6 cases per 100,000 annually.

Acute encephalitis of viral origin

75 patients with acute encephalitis of confirmed or suggestive viral or virus-like etiology showed a predominance of herpes simplex virus (HSV) as an etiological agent (13.3-32.0%) in all age groups without seasonal variation and increasing in number during years. Mumps, occurring mainly in female patients, was next in order and thereafter coxsackievirus B, varicella-zoster, and adenoviruses, followed by multiple coincident infections, and a large number of occasional agents. HSV seems to have displaced tick-borne encephalitis virus as the major cause of acute encephalitis in Finland. Pregnancy appeared to increase susceptibility to HSV encephalitis. The outcome was associated with the etiological agent in the first hand, HSV and nonviral microbes appeared unfavourable, but also with the clinical symptomatology, particularly altered consciousness, mental symptoms and focal neurological signs. The need for exact and rapid diagnosis in all cases of acute encephalitis is underlined in view of the possibility of specific therapy.