Meningitis

Meningitis refers to inflammation of the meninges, the protective membranes covering the brain and spinal cord. It is a serious condition caused by various pathogens, including bacteria, viruses, fungi, and parasites.

Key Points

• Meningitis can lead to severe complications such as brain damage, hearing loss, and death.
• Early diagnosis and treatment are critical to reducing morbidity and mortality.
• Common pathogens include Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae.
• Management includes antimicrobial therapy, supportive care, and prevention through vaccination.

Etiology and Pathogenesis

Causes

• Bacterial pathogens: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, Acinetobacter baumannii.
• Viral pathogens: Enteroviruses, herpesviruses, mumps virus.
• Fungal pathogens: Cryptococcus neoformans (common in immunocompromised patients).
• Parasitic causes: Rare but include Naegleria fowleri (primary amoebic meningoencephalitis).
• Non-infectious causes: Autoimmune diseases, certain medications, cancer.

Pathogenesis

• Pathogens invade the meninges and trigger an inflammatory response.
• Increased vascular permeability and disruption of the blood-brain barrier lead to cerebral edema and elevated intracranial pressure.
• Cerebrospinal fluid (CSF) changes: increased white blood cells, protein, and decreased glucose levels.
• Neurological dysfunction results from brain tissue damage, circulatory disturbances, and immune-mediated injury.

Clinical Features

• Early symptoms:
• Fever, headache, nausea, vomiting.
• Stiff neck (nuchal rigidity).
• Photophobia and altered mental status.
• Advanced symptoms:
• Seizures, focal neurological deficits.
• Impaired consciousness, coma.
• Signs of increased intracranial pressure: papilledema, bradycardia, hypertension.

Diagnosis

• Clinical examination:
• Kernig’s sign: pain on knee extension with hip flexed.
• Brudzinski’s sign: neck flexion causes hip/knee flexion.
• Lumbar puncture:
• CSF analysis: elevated white blood cells, high protein, low glucose in bacterial meningitis.
• Gram stain and culture for pathogen identification.
• Imaging:
• CT or MRI to rule out mass effect or abscess before lumbar puncture.

Treatment Principles

General Measures

• Hospitalization for close monitoring and supportive care.
• Manage intracranial pressure: elevate head of bed, osmotic therapy (e.g., mannitol).
• Seizure control with antiepileptic drugs if needed.

Antimicrobial Therapy

• Bacterial meningitis:
• Empiric antibiotics: ceftriaxone or cefotaxime plus vancomycin.
• Add ampicillin for Listeria monocytogenes in neonates, elderly, or immunocompromised.
• Viral meningitis:
• Supportive care; acyclovir for suspected herpesvirus.
• Fungal meningitis:
• Amphotericin B and flucytosine for Cryptococcus; fluconazole for maintenance.

Adjunctive Therapy

• Corticosteroids: Dexamethasone to reduce inflammation in bacterial meningitis (especially pneumococcal).
• Vaccination: Preventive vaccines for N. meningitidis, S. pneumoniae, and H. influenzae.

Prevention

• Routine immunization against meningococcal, pneumococcal, and Haemophilus influenzae type b (Hib).
• Prophylactic antibiotics for close contacts of meningococcal cases.
• Maintain good hygiene and avoid close contact with infected individuals.

Complications and Referral

• Complications:
• Hearing loss, hydrocephalus, brain abscess.
• Sepsis, disseminated intravascular coagulation (DIC).
• Referral criteria:
• Persistent neurological deficits, recurrent meningitis.
• Suspected complications requiring neurosurgical intervention.

Patient Education

• Seek immediate medical attention for symptoms of meningitis.
• Complete prescribed treatments and attend follow-up appointments.
• Encourage vaccination to prevent meningitis.