What is meningitis?

Meningitis is an inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation is typically caused by an infection, although it can also result from non-infectious causes such as chemical irritation, drug reactions, or autoimmune disorders. Meningitis is a serious condition that requires prompt medical attention and treatment.

There are several types of meningitis, including:

1. Bacterial meningitis: Bacterial meningitis is caused by bacterial pathogens infecting the meninges. It is often severe and can lead to life-threatening complications if not treated promptly. Common bacterial pathogens associated with bacterial meningitis include Streptococcus pneumoniae (pneumococcal meningitis), Neisseria meningitidis (meningococcal meningitis), Haemophilus influenzae type b (Hib meningitis), and Listeria monocytogenes. Bacterial meningitis can spread through respiratory droplets, close contact with an infected individual, or bloodstream dissemination from other infections in the body.

2. Viral meningitis: Viral meningitis is caused by viral infections, most commonly enteroviruses such as echovirus and coxsackievirus. Other viruses, including herpes simplex virus (HSV), varicella-zoster virus (VZV), and mumps virus, can also cause viral meningitis. Viral meningitis is generally less severe than bacterial meningitis and often resolves on its own with supportive care. It is typically transmitted through respiratory droplets or fecal-oral route.

3. Fungal meningitis: Fungal meningitis is caused by fungal pathogens infecting the meninges, such as Cryptococcus neoformans, Candida species, and Histoplasma capsulatum. Fungal meningitis is less common than bacterial or viral meningitis but can occur in individuals with weakened immune systems, such as those with HIV/AIDS, organ transplant recipients, or individuals receiving immunosuppressive therapy. Fungal meningitis may develop slowly and can be difficult to diagnose and treat.

4. Parasitic meningitis: Parasitic meningitis is caused by parasitic infections of the central nervous system, such as Naegleria fowleri (primary amebic meningoencephalitis), Angiostrongylus cantonensis (eosinophilic meningitis), or Taenia solium (neurocysticercosis). Parasitic meningitis is rare but can occur in individuals exposed to contaminated water, soil, or food sources.

5. Non-infectious meningitis: Non-infectious meningitis can result from non-infectious causes such as autoimmune disorders (e.g., lupus, Behçet's disease), drug reactions (e.g., nonsteroidal anti-inflammatory drugs, antibiotics), chemical irritants, or malignancies. Non-infectious meningitis may have similar clinical manifestations to infectious meningitis but requires different management approaches.

The symptoms of meningitis can vary depending on the underlying cause, the severity of inflammation, and individual factors such as age and immune status. Common symptoms of meningitis may include:

• Fever
• Headache
• Stiff neck (neck stiffness)
• Photophobia (sensitivity to light)
• Altered mental status (confusion, irritability, lethargy)
• Nausea and vomiting
• Rash (in some cases of meningococcal meningitis)
• Seizures
• Focal neurological deficits (weakness, sensory loss)

The diagnosis of meningitis typically involves a combination of clinical evaluation, laboratory tests (such as cerebrospinal fluid analysis), imaging studies (such as CT scan or MRI), and sometimes additional diagnostic procedures (such as blood cultures or PCR testing). Treatment of meningitis depends on the underlying cause and may include antibiotics (for bacterial meningitis), antiviral medications (for viral meningitis), antifungal medications (for fungal meningitis), supportive care, and management of complications.

Meningitis is a medical emergency that requires prompt diagnosis and treatment to prevent complications such as brain damage, seizures, coma, or death. Vaccination against certain bacterial pathogens (such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b) and practicing good hygiene (such as handwashing and respiratory hygiene) can help prevent some cases of bacterial and viral meningitis.