Aetiopathogenesis of CNS Infections
AbstractDespite decades of dramatic progress in the prevention and treatment of infectious diseases (ID), it contineus to challenge the physicians diagnostic skill and remains a major cause of death and disability worldwide. Infectious agents are also increasingly recognized in the aetiology of non-infectious diseases. CNS infections include meningitis, Encephalitis, Myelitis, intracranial. Thrombophlebitis, brain abscess infected subdural hematoma as well as granulomatous disease due to TB, syphilis, fungal infections and plausibily sarcoidosis.
In adults, pneumococcus, meningococcus and H.influenza account for about 80-90% of bacterial meningitis whilst in infants and children aged between 2 months to 7 years, H.influenza infeciton is common. Five viral syndromes are recognized and include myelitis/radiculitis; herpes zooster ganglionitis, acute aseptic meningitis, acute encephalitis or meingo-encephalitis and chronic infections due to “slow viruses”/unconventional agents simulating degenerative diseases.
Conventional viruses cause sub-acute sclerosing pan-encephalitis, progressive rubella panencephalitis, and progressive multifocal leukoencephalopathy; while unconventional agents cause prion diseases which include kuru, sub-acute spongiform encephalopathy, Gestman Straussler sheinker (GSS) and familial fatal insominia.
The clinical and pathological effects of these infections are diverse as the CNS is uniquely protected from pertubation by the blood brain barrier. The cerebral tissue is also resistant to infeciton, a necessary antecedant to susceptibility being infarction by arterial occlusion (embolism) or venous occlusion (thrombophlebitis).
Nig. Medical Practitioner Vol. 45(1/2) 2004: 14-19