Cerebral Infxn

Meningitis Meningitis is an inflammation of the pia mater and arachnoid membranes that surround the brain and the spin al cord. The SAS between these two meninges contains CSF that may reflect the signs and symptoms of the meninges. Pathophysiology and Etiology: •

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The organisms causing these infections seem to vary depending on the age and immune status of the patient. The mortality is 5% for children who recovermay have long term neurologic problems (eg. Hearing deficit). These organisms may have epidemic potential. Viral meningitis is the most common form and is usually self limiting. Management is supportive. It is usually caused by a nonpolio enterovirus(90%). It targets children and the elderly. This organism is spread by the fecal-oral route and through sewage. Bacterial meningitis may cause damage to the CNS from the inflammatory process rather than the pathogen. Bacterial meningitis is usually more serious than the viral meningitis. It is typically caused by streptococcus pneumoniae (pneumococcal meningitis), a gram positive diplococci, and Neisseria meningitis (meningococcal meningitis), a gram negative diplococci. o With a mortality of 30%, S. pneumoniae is the leading cause of bacterial meningitis in children younger than age 5. it is spread by droplet. o Most bacteria that cause meningitis begin by colonizing the nasopharynx, then invade the circulation and CSF, causing inflammatory response mediated by cytokines. o Bacterial meningitis can result in brain damage due to chemicals released by bacteria that kill or damage neurons, purulent exudates that may result in vascilitis and vasospasm, and increased ICP that causes cerebral edema. Fungal meningitis, particularly Cryptococcus neoformans, affects immunosuppressed patients 9eg Human immunodeficiency virus [HIV] through soil contaminated with excrement from pigeons and chickens. Cryptococcal antigen, or culture, is found in the CSF, but meningeal signs may be minimal. In HIV-positive patients, tuberculous meningitis, tuberculomas, and atypical mycobacteria infections of the brain may be noted. Parasitic meningitis is usually cause by flukes, worms, or amoeba. Hospital-acquired postcraniotomy meningitis by gram-negative bacilli, can result in mortalities of 30%, multiple craniotomy operations place the patient at even risk. It develops approximately 7 to 8 days postoperatively. Neoplastic meningitis affects approximately 3% to 8% of patients who have systemic cancers. The mean survival time is approximately 5 to 8 months. In neoplastic meningitis, malignant cells infiltrate the leptomeninges as a complication of breast cancer, lung cancer, malignant melanoma, non-hodgkin’s lymphoma, and acute leukemia.

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Meningitis is the primary intracranial complication of acute and chronic sinusitis (sphenoid sinusitis most common). S. pneumonia and Staphylococcus aureus are the most common organism. Listeria monocytogenes, a gram-positive bacillus, may cause meningitis through contaminated hotdogs, cold meats anunpasteurized dairy products. The incidence of Haemophilus influenza meningitis has decreased due to the Haemophilus b vaccine.