Meningitis
Meningitis is inflammation of the membranes (meninges) that surround the brain and spinal cord. It can develop from bacterial, viral, fungal or parasitic causes. Bacterial meningitis is the most serious form and, if not treated urgently, can lead to death or permanent neurological damage within hours to days; viral meningitis usually follows a milder course. The classic triad is fever, headache and neck stiffness. Diagnosis is made by lumbar puncture and analysis of the cerebrospinal fluid (CSF).
最終更新: 2026-06-07
Definition and Organisms
Meningitis is inflammation of the subarachnoid space and the cerebrospinal fluid (CSF). Bacterial meningitis is most often caused by Streptococcus pneumoniae and Neisseria meningitidis; with the spread of vaccination, Haemophilus influenzae has declined. In neonates, group B streptococcus, E. coli and Listeria predominate; in the elderly and immunosuppressed patients, Listeria and gram-negative bacteria come to the fore. Viral meningitis is most often caused by enteroviruses. Fungal and tuberculous meningitis follow a chronic course and are usually seen in immunosuppressed patients.
Pathogenesis
In bacterial meningitis, the organisms first colonize the nasopharynx, cross the mucosa into the blood (bacteremia) and reach the subarachnoid space across the blood-brain barrier. Bacterial replication in the CSF triggers a strong inflammatory response; cytokine release, increased blood-brain barrier permeability, cerebral edema, raised intracranial pressure and cerebral ischemia may develop. Direct spread from adjacent infections such as sinusitis, otitis media and mastoiditis, or from a CSF leak due to a skull base fracture, is another mechanism.
Symptoms
The classic triad of fever, severe headache and neck stiffness is present together in nearly half of patients; however, at least two of these features are present in the great majority. Accompanying findings are photophobia, nausea-vomiting, altered consciousness and seizures. In Neisseria meningitidis meningitis, a petechial/purpuric rash may be seen and a rapidly progressive severe picture (Waterhouse-Friderichsen syndrome) may develop. In infants, irritability, feeding difficulty and a bulging fontanelle; in the elderly, an atypical picture and confusion may predominate.
Diagnosis
Lumbar puncture and CSF analysis are the gold standard for diagnosis. In bacterial meningitis the CSF appears cloudy; the white cell count is markedly increased (neutrophil-predominant), protein is high and glucose is low. In viral meningitis the rise in white cells is lower (lymphocyte-predominant) and glucose is normal. Gram staining and CSF culture identify the organism; blood cultures taken before antibiotics and rapid PCR tests contribute to diagnosis. In selected situations such as an immunosuppressed patient, new seizure, papilledema, focal neurological deficit or impaired consciousness, brain CT is requested before lumbar puncture.
Treatment — Bacterial Meningitis
Bacterial meningitis is an emergency; every hour of delay worsens the prognosis. When suspected, empirical antibiotics are started within the first hour immediately after blood cultures are obtained, without waiting for lumbar puncture results if necessary. Empirical therapy is selected according to age and risk factors (often a third-generation cephalosporin with vancomycin; ampicillin is added for Listeria cover in elderly or immunosuppressed patients). Treatment is then targeted according to culture results. Dexamethasone (a corticosteroid), when started immediately before or together with antibiotics, reduces the risk of sequelae such as hearing loss, especially in pneumococcal meningitis.
Prevention and Prognosis
Vaccination is the most effective means of prevention: Haemophilus influenzae type b, pneumococcal and meningococcal vaccines are included in routine programs. In Neisseria meningitidis meningitis, antibiotic prophylaxis is recommended for close contacts within the first 24 hours. Viral meningitis usually resolves spontaneously with supportive treatment (aciclovir is given in HSV meningitis). In bacterial meningitis, mortality is not low even with early treatment, and a significant proportion of survivors may have permanent sequelae such as hearing loss, cognitive impairment or epilepsy. Outcomes are individual and cannot be guaranteed.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:340-343.
- Tunkel AR, Hartman BJ, Kaplan SL, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis. 2004;39(9):1267-1284.
- van de Beek D, Cabellos C, Dzupova O, et al. ESCMID guideline: diagnosis and treatment of acute bacterial meningitis. Clin Microbiol Infect. 2016;22(Suppl 3):S37-S62.
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