ACUTE VIRAL MENINGITIS

Clinical Manifestations- fever, headache, and meningeal irritation

- headache usually frontal or retroorbital with photophobia and pain on moving the eyes

- with malaise, myalgia, anorexia, nausea and vomiting, abdominal pain and/or diarrhea- mild degree of lethargy and drowsiness

- seizures or other focal neurologic signs or symptoms indicates of involvement of brain parenchyma

Epidemiology- some viruses have seasonal predilections: increased incidence during summer and early fall

Laboratory Diagnosis

(1) CSF examination- most important lab test

- lymphocytic pleocytosis (25-500 cells/μL)- normal to slightly elevated protein (20-80 mg/dL)- normal glucose (may be decreased in mumps and

LCMV)- normal to mildly elevated opening pressure

- organisms are not seen on Gram’s stain or AF stained smears or India ink preparations

- PMNs may predominated in the first 48 hrs.- As a rule, lymphocytic pleocytosis with low glucose

suggest fungal, listerial, or TB meningitis or noninfectious disorders

(2) PCR of viral nucleic acid- procedure of choice for HSV meningitis- more sensitive than viral cultures- used routinely to diagnose CMV, EBV, VZV

(3) CSF culture- 2 mL of CSF, refrigerated and processed ASAP

- never stored in ~200C, virus unstable at this temp.

- should be in a ~700C freezer if stored for >20 hrs.(4) Other sources of viral isolation

- throat, stool, blood, urine- enterovirus in stool is not diagnostic

(5) Serologic studies- useful for arboviruses- less useful for HSV, VZV, CMV, EBV

- diagnosis of acute viral infection can be made by documenting seroconversion between acute-phase and convalescent sera or by demonstrating the presence of virus-specific IgM antibodies

- IgM Abs persist for only a few months after acute infection except WNV IgM

- useful mainly for retrospective establishment of a specific diagnosis

- the finding of oligoclonal bands in electrophoresis may be suggestive of certain viruses

(6) Other lab studies- CBC, liver function tests, ESR, BUN, plasma levels of electrolytes, glucose, creatinine, creatine kinase, aldolase, amylase, and lipase

Differential Diagnosis

(1) bacterial meningitis(2) parameningeal infections or partially treated bacterial

meningitis

(3) nonviral infections meningitides with culture negative (fungal, tuberculous, parasitic, syphillis)

(4) neoplastic meningitis(5) meningitis secondary to noninfectious inflammatory

diseases

Specific Viral Etiologies

(1) Enterovirus - most common cause of viral meningitis- typical case occurs in the summer months, esp. in

children < 15 y/o- PE includes exanthemata, hand-foot-mouth disease,

herpangina, pleurodynia, myopericarditis, hemorrhagic conjunctivitis

- diagnosis by PCR amplification of enteroviral RNA from CSF

(2) Arbovirus - typically occur in the summer- WNV suspected when cluster of meningitis cases are

preceded by death of birds in a certain geographic region

- history of tick exposure sought in cases of Colorado tick fever or Powassan virus infection

(3) HSV-2 - probably the second most common viral cause of

meningitis- cultures are invariably negative- diagnosis made by CSF PCR- genital lesions may not be present

(4) VZV- suspected in the presence of concurrent chicken pox

or shingles- 40% occur in the absence of rash- Can also produce cerebellar ataxia- CSF PCR used in the diagnosis

(5) EBV- may occur with or without evidence of infectious

mononucleosis syndrome- diagnosis suggested by atypical lymphocytes in the

CSF or in the peripheral blood- diagnose by SF PCR- patient with CNS lymphoma may be positive in PCR

in the absence of meningoencephalitis(6) HIV

- presence of HIV genome by PCR or p24 protein establishes the diagnosis

- cranial nerve palsies common(7) Mumps

- typically occurs in late winter or early spring, esp. in males

- orchitis, oophoritis, parotitis, pancreatitis, or elevations in serum lipase and amylase are suggestive but can be found with other viruses

- infection confers lifelong immunity- diagnosis made by isolation from CSF and/or

demonstration of seroconversion(8) LCMV

- typically occurs late fall or winter in individuals with history of exposure to rodents or their excreta

- with rash, pulmonary infiltrates, alopecia, parotitis, orchitis, or myopericarditis

- leucopenia, thrombocytopenia, abnormal liver function tests

Treatment- in the usual case, treatment is symptomatic and

hospitalization is not required

- patient left undisturbed in a quiet, darkened room- analgesics and antipyretics- monitor fluid and electrolyte status because

hyponatremia and SIADH may develop- oral or IV acyclovir for HSV, VZV and EBV- highly active retroviral therapy for HIV meningitis- for patient with known deficient humoral immunity,

give IM or IV IgG

- pleconaril for enteroviral infections- vaccination (Varivax) for VZV, booster may be

required to maintain immunity

Prognosis- most of the times, there’s full recovery- outcome in < 1 y/o: intellectual impairment, learning disabilities, hearing loss