Meningitis

Definition:

• Meningitis is an inflammation of the membranes (meninges) surrounding the brain and spinal cord. It can be caused by infections (viral, bacterial, fungal) or non-infectious factors (e.g., drugs, autoimmune diseases).

Etiology:

1. Bacterial Meningitis:
   • More severe; common organisms include Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae.
2. Viral Meningitis:
   • Often less severe; common viruses include enteroviruses, herpes simplex virus, and varicella-zoster virus.
3. Fungal Meningitis:
   • Less common; seen in immunocompromised individuals.

Epidemiology:

• Incidence and prevalent organisms vary by age, region, and vaccination status.

Pathophysiology:

• Infection or other inflammatory triggers cause the meninges to swell, which can affect the brain and spinal cord, potentially leading to life-threatening complications.

Clinical Features:

• Classic triad: Fever, headache, and neck stiffness.
• Other symptoms: Nausea, vomiting, photophobia, altered mental status.
• In infants, symptoms may be nonspecific: irritability, poor feeding, bulging fontanelle.
• Kernig’s and Brudzinski’s signs may be present.

Diagnosis:

• Lumbar puncture with cerebrospinal fluid (CSF) analysis is crucial: elevated white cell count, elevated protein, and decreased glucose in bacterial meningitis; lymphocytic predominance in viral meningitis.
• Blood cultures, CT or MRI before lumbar puncture if raised intracranial pressure is suspected.
• PCR and antigen tests for specific pathogens.

Management:

• Bacterial meningitis: Immediate empirical intravenous antibiotics and sometimes corticosteroids.
• Viral meningitis: Supportive care; specific antivirals for cases like herpes simplex.
• Fungal meningitis: Antifungal therapy.
• Vaccination for prevention: Pneumococcal, meningococcal, and Haemophilus influenzae type b (Hib) vaccines.

Prognosis:

• Bacterial meningitis can be fatal if not treated promptly and carries risk of serious complications like hearing loss, brain damage, or learning disabilities.
• Viral meningitis generally has a good prognosis.