meningitis

meningitis
Name	Meningitis
Caption	The meninges (dura mater, arachnoid mater, and pia mater) are the protective membranes surrounding the brain and spinal cord.
Field	Infectious disease, Neurology
Symptoms	Fever, headache, neck stiffness
Complications	Deafness, Epilepsy, Hydrocephalus, Cognitive deficit
Onset	Rapid (acute)
Types	Bacterial meningitis, Viral meningitis, Fungal meningitis
Causes	Bacteria, Viruses, Fungi, Parasites, non-infectious factors
Risks	Age, Immunosuppression, Crowding
Diagnosis	Lumbar puncture, Cerebrospinal fluid analysis
Differential	Brain abscess, Subarachnoid hemorrhage, Systemic lupus erythematosus
Prevention	Vaccination, Antibiotics
Treatment	Antibiotics, Antivirals, Corticosteroids
Prognosis	Varies by cause
Frequency	~1.2 million cases annually worldwide
Deaths	~135,000 annually

meningitis. Meningitis is an acute inflammation of the protective membranes covering the brain and spinal cord, collectively known as the meninges. This inflammation is most commonly triggered by an infection with microorganisms such as bacteria, viruses, or fungi, though non-infectious causes also exist. The condition is a medical emergency due to its proximity to the central nervous system and potential for severe neurological sequelae or death, necessitating prompt diagnosis and management.

Signs and symptoms

Classic symptoms in adults and older children include the triad of sudden onset fever, intense headache, and neck stiffness, often accompanied by photophobia and phonophobia. In infants, symptoms may be non-specific, manifesting as irritability, lethargy, poor feeding, or a bulging fontanelle. Severe cases can rapidly progress to altered mental status, seizures, and coma, indicative of significant cerebral involvement. The presence of a characteristic rash, such as the non-blanching petechiae or purpura associated with Neisseria meningitidis, is a critical clinical sign. Certain pathogens may also cause specific neurological deficits, such as cranial nerve palsies, which can be detected during a thorough neurological examination.

Causes

The most common causes are infectious agents, with bacteria and viruses predominating. Leading bacterial pathogens include Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae, the latter now largely controlled in regions with widespread vaccination programs. Viral causes are often due to enteroviruses, though herpes simplex virus and the mumps virus are also implicated. Less commonly, fungi such as Cryptococcus neoformans can cause disease, particularly in individuals with HIV/AIDS or other forms of immunosuppression. Non-infectious etiologies encompass medications like NSAIDs, autoimmune diseases such as systemic lupus erythematosus, and the spread of cancer cells from malignancies like leukemia.

Diagnosis

Definitive diagnosis requires analysis of the cerebrospinal fluid obtained via a lumbar puncture. Key findings in the fluid include elevated white blood cell count, altered levels of glucose and protein, and the identification of the causative organism through Gram stain, culture, or polymerase chain reaction testing. Prior to performing a lumbar puncture, neuroimaging with a CT scan is often recommended to rule out conditions like brain abscess or mass effect that could contraindicate the procedure. Blood tests, including blood cultures, C-reactive protein, and procalcitonin levels, provide supportive evidence and help differentiate between bacterial and viral origins.

Prevention

Primary prevention is achieved through vaccination. Major vaccines include the meningococcal vaccine against Neisseria meningitidis, the pneumococcal conjugate vaccine against Streptococcus pneumoniae, and the Haemophilus influenzae type b vaccine. Prophylactic antibiotics, such as rifampicin or ciprofloxacin, are recommended for close contacts of individuals diagnosed with meningococcal disease to prevent secondary cases. Public health measures, including those implemented by the World Health Organization, focus on outbreak control in crowded settings like college dormitories or during the annual Hajj pilgrimage. General hygiene practices, like handwashing, help reduce the spread of enteroviruses.

Treatment

Initial management is urgent and often empirical. Suspected bacterial cases require immediate intravenous administration of broad-spectrum antibiotics, such as ceftriaxone or vancomycin, sometimes in combination with ampicillin. Adjunctive therapy with corticosteroids, typically dexamethasone, is recommended in certain bacterial cases to reduce neurological complications. Viral meningitis is usually managed supportively with analgesics, antipyretics, and hydration, though specific antivirals like acyclovir are used if herpes simplex virus is suspected. Fungal infections are treated with long courses of antifungals such as amphotericin B and fluconazole, often under the guidance of specialists from the Centers for Disease Control and Prevention.

Prognosis

Outcomes vary dramatically based on the causative agent, speed of treatment initiation, and the patient's age and underlying health. Bacterial meningitis carries a significant risk of mortality and long-term disability, including sensorineural hearing loss, cognitive impairment, and motor deficits. Viral meningitis typically follows a benign, self-limiting course with full recovery, though exceptions exist with viruses like West Nile virus. Survivors may require extensive rehabilitation and long-term follow-up with specialists in neurology or otolaryngology to manage sequelae. Global mortality remains high, particularly in the African meningitis belt, where outbreaks of Neisseria meningitidis serogroup A historically caused high case fatality rates.

Category:Infectious diseases Category:Neurological disorders