Meningitis

Meningitis is an inflammation of leptomeninges and underlying subarachnoid cerebrospinal fluid (CSF), whereas encephalitis is an inflammation of the brain parenchyma . Meningitis and encephalitis are life – threatening infections especially in children as any infectious agent can cause central nervous system (CNS) infection because of the inflammation's proximity to the brain and spinal cord; therefore the condition is classified as a medical emergency (CDC , 2009).

Aseptic Meningitis (AM) is a febrile meningial inflammation characterized by CSF mononuclear pleocytosis ,normal glucose, mild elevation in protein and absence of bacteria agents . Viral meningitis which is the most common form of AM is an infection of the meninges by one of different viruses or occurs as an uncommon complications of systemic viral infection ((Sergio et al., 2007 & Scheld et al ., 2004).

Human Enteroviruses (EVs) are the most common causes of adult AM and together with herpes simplex virus type 1 (HSV-1) are the main causes of meningitis in adult and children especially in areas with vaccination( Desmond et al., 2006). While in areas with low vaccination , measles and mumps viruses are often the most common causes of meningitis (Frantzidou et al ., 2008 & Moran ; 2003 ).

Approximately half cases of viral meningitis are caused by coxsackie and echovirus types of enterovirus ( Caro et al ., 2001).

Mycobacterium TB, mycoplasma and leptospira can also cause AM ( Avery et al.,2006).Tuberculous meningitis is the second most frequently cause of infectious AM in Egypt with

the highest mortality rate among the other causes of meningitis ( Van den Bos et al ., 2004).

AM may also result from infection by treponema pallidum , borrelia burgdorferi and malaria (Jordan & Durso, 2005). Cryptococcus neoformans is a form of fungal meningitis that typically seen in AIDS, while amoebic meningitis caused by Naegleria fowleri is contracted from freshwater sources (Sloan et al ., 2008 & Ginsberg ,2004).

AM may also caused by several non-infectious causes as cancer (malignant meningitis)( Chamberlain, 2005 & Tunkel et al ., 2004). Drugs as non-steroidal anti-inflammatory agents, antibiotics and intravenous immunoglobulins also can cause AM (Moris & Garcia-Monco , 1999).

Laboratory diagnosis of viral meningitis relied on virus isolation and this method has several limitations as it needs long duration from days to weeks with limited sensitivity , virus antigen and antibody detection (Kupila et al ., 2005).

For the diagnosis of M. tuberculosis , a number of laboratory techniques can be used that differ in their sensitivity, cost and time. They include acid-fast staining, isolation on Lowenstein Jensen media and radiometric method (BACTC) .Molecular methods as polymerase chain reaction (PCR) and Gen-probe identification methods can also be used (Thwaites et al. , 2005).

PCR is used to identify the pathogens in CSF . It is sensitive and specific test. It is also used in distinguishing the various causes of viral meningitis ( Pandit et al ., 2005).