Meningitis is inflammation of the meninges, the membranes that cover the brain and spinal cord. It is commonly caused by infection, but other causes include chemical irritants, drug allergies, fungi, and tumors. Based on the clinical evolution of the illness and the type of inflammatory exudate present in the cerebral spinal fluid (CSF), infectious meningitis is categorized into acute pyogenic (usually bacterial), aseptic (usually viral), and chronic (usually tuberculosis, spirochetal, cryptococcal).
Early diagnosis is essential for bacterial meningitis because it can result in death or brain damage if left untreated. In bacterial meningitis, a correlation exists between bacterial organism and age. The most likely organism in neonates may be Escherichia Coli or group B Streptococci. In the elderly, it may be Streptococcus Pneumonia or Listeria Monocytogenes. In young adults, it may be Neisseria Meningitides. In contrast, most viral infections are due to enteroviruses but only a small number of people who develop enteroviral infections present with meningitis. Other viral infections that can cause meningitis include mumps, herpes virus, measles, and influenza. Chronic meningitis can be caused by pathogens such as mycobacteria and spirochetes. Thus, medical attention is necessary to differentiate between bacterial, viral, and chronic meningitis.
Risk factors include individuals over the age of 60 or below the age of 5, diabetes mellitus, renal or adrenal insufficiency, hypoparathyroidism, cystic fibrosis, immunosuppression, HIV, crowding (military recruits and college residents), recent exposure to those with meningitis, etc. The symptoms have a rapid onset and include fever, chills, mental status changes, nausea, vomiting, photophobia, severe headache, and meningismus (stiff neck). Additional symptoms include agitation, bulging fontanelles, decreased consciousness, tachypnea, poor feeding or irritability in children, and opisthotonos (unusual posture, with head and neck, arched backward).
To confirm a diagnosis, a lumbar puncture (spinal tap) should generally be performed on anyone suspected of meningitis to sample and culture the CSF for abnormal cell counts, glucose, and protein. Other diagnostic tests include blood culture, chest x-ray, and MRI or CT scan of the head. The underlying cause of meningitis needs to be determined to administer proper treatment and define the severity of each case. Unlike bacterial meningitis, viral meningitis usually does not involve treatment and patients generally recover within two weeks; however, in certain instances (such as with the herpes simplex virus) antiviral medications may be indicated.
Antibiotic treatment for bacterial meningitis is dependent on the underlying bacterium. By treating the most common types, the risk of dying is reduced to below 15%. Symptoms such as brain swelling, shock, and seizures are treated with other medications and intravenous fluids. Possible complications of meningitis include brain damage, subdural effusion, hearing loss, hydrocephalus, and seizures. To prevent contraction of meningitis, the meningococcal vaccination is recommended for populations at risk.