Viral meningitis Flashcards
what is the definition of viral meningitis?
Viral meningitis is inflammation of the meninges caused by a variety of different viruses and is the most common cause of aseptic meningitis.
what is the epidemiology of viral meningitis?
Most common cause of meningitis in UK
Most commonly diagnosed in children
what is the aetiology of viral meningitis?
Human enteroviruses are the most common cause of viral meningitis; they account for most cases (at all ages) in which the cause is identified. They include coxsackieviruses, echoviruses, and polioviruses. Herpes viruses cause a spectrum of central nervous system (CNS) disease, including meningitis, myelitis, and encephalitis. Herpes simplex virus (HSV)-1 is the most common cause of viral encephalitis in the Western world, whereas HSV-2 is more commonly associated with viral meningitis. Varicella zoster virus is a relatively common cause of viral meningitis, which may occur during primary infection or with shingles but may occur without any rash.
what are the risk factors for viral meningitis?
Infants Young adults Older people Summer and autumn Exposure to vector (mosquito or tick) Unvaccianted for mumps
what is the pathophysiology of viral meningitis?
Enteroviruses are spread by the faecal-oral route. The non-polio enteroviruses and arboviruses initially replicate outside the CNS in tissues such as muscle, liver, and the respiratory or gastrointestinal tracts, and then reach the CNS by haematogenous spread. Viral penetration of the blood-brain barrier occurs by either infection of endothelial cells or of migrating leukocytes. It is unclear whether HSV infects the CNS as a result of haematogenous spread or by retrograde spread along peripheral nerves. Once within the CNS, viruses spread through the subarachnoid space leading to meningitis, and may go on to infect neurons and glial cells leading to encephalitis or myelitis. The cellular immune response to viral infection of the CNS leads to the accumulation of lymphocytes within the cerebrospinal fluid (CSF) and the release of inflammatory cytokines such as interleukin (IL)-6 and TNF. The inflammatory response increases the permeability of the blood-brain barrier and this allows diffusion of circulating immunoglobulins into the CSF
what are the key presentations for viral meningitis?
Risk factor precedence Headache Photophobia Neck stiffness Fever Nausea and vomiting Rash Kernig and brudzinski’s signs (uncommon)
what are the first line and gold standard investigations for viral meningitis?
Blood cultures - negative
FBC - WBC mildly elevated
CRP - normal or elevated
Serum urea creatinine and electrolytes - normal
Blood gas - normal
Blood glucose - CSF:blood glucose ratio may be normal or mildly lowered
CSF microscopy - WBC count elevated; typically 5-1000 cells/mm3 for children and adults and >20 cells/mm3 for neonates
CSF gram stain - negative
CSF bacterial culture - negative
CSF protein - normal or elevated
CSF glucose - may be low
CSF lactate - low
CSF stool and throat swab PCR for viral pathogens - may be positive
HIV serology - aseptic meningitis could mean HIV
what are the differential diagnoses for viral meningitis?
Bacterial meningitis
Encephalitis
Encephalopathy
how is viral meningitis managed?
Treat all patients with suspected meningitis in line with guidelines on bacterial meningitis until the diagnosis of bacterial meningitis is excluded or deemed unlikely
Confirmed viral:
No effective treatment. Paracetamol and ibuprofen, codeine (supportive treatments)
what are the complications of viral meningitis?
Persistent headache and malaise
Neuro-developmental defect in infants
what is the prognosis for viral meningitis?
Outcome in most people with viral meningitis is generally good. However, headache and malaise may persist for weeks in adults, particularly following meningitis caused by herpes simplex virus
