Prognosis

Morbidity

Generally, with prompt and adequate antimicrobial and supportive therapy, the outcome after acute bacterial meningitis is excellent. However, prognosis depends on multiple factors such as age, presence of comorbidity, causative pathogen, and severity at presentation.

In adults with bacterial meningitis, risk factors associated with a poor prognosis include advanced age, presence of osteitis or sinusitis, low Glasgow Coma Scale score on admission (i.e., low level of consciousness), tachycardia, absence of rash, thrombocytopenia, elevated erythrocyte sedimentation rate, low cerebrospinal fluid cell count, and positive blood culture.[43] Up to one third of adults who have had bacterial meningitis have cognitive impairment.[158] One recent meta-analysis looking at patients with bacterial meningitis documented cerebral infarcts in 16% of patients.[159]

About 10% to 20% of children who survive bacterial meningitis develop severe sequelae such as sensorineural hearing loss, motor problems, seizures, and significant cognitive impairment.[160][161][162]​ From 20% to 30% of children have more subtle adverse outcomes such as cognitive, academic, and behavioral problems.[163]

Mortality

According to the World Health Organization, 1 in 6 patients who contract bacterial meningitis will die from the disease.[7]

In one global meta-analysis that looked at case fatality rates due to bacterial meningitis from 1935 to 2019, the overall case fatality ratio was 18% (95% CI, 16% to 19%), decreasing from 32% (95% CI, 24% to 40%) before 1961 to 15% (95% CI, 12% to 19%) after 2010. The overall fatality rates were 19.3% in both neonates and adults, and 14.8% in children. It was highest in meningitis caused by Listeria monocytogenes at 27% (95% CI, 24% to 31%) and pneumococci at 24% (95% CI, 22% to 26%), compared with meningitis caused by meningococci at 9% (95% CI, 8% to 10%) or Haemophilus influenzae at 11% (95% CI, 10% to 13%). Meta-regression showed decreasing case fatality ratios overall and stratified by Streptococcus pneumoniae, Escherichia coli, or Streptococcus agalactiae (P < .001).[164]

In the US, cases of meningococcal disease have increased since 2021 and now exceed pre-pandemic levels. In 2023, 438 confirmed and probable cases were reported. This is the largest number of US meningococcal disease cases reported since 2013. Neisseria meningitidis serogroup Y drives much of this recent increase. People disproportionately affected by the increase include patients between the ages of 30 and 60 years, black or African-American patients and adults with HIV.[24]

Approximately 30% of people with meningococcal disease present with meningococcemia.[165]​ Patients with meningococcal sepsis have a higher fatality rate, with studies ranging from 20% to 80%.[166]

Most deaths occur in the first 24 hours of illness. Mortality is higher in adolescents than in younger children, and higher during outbreaks than in sporadic disease.[167] Delayed antibiotic administration increases mortality.​[59][101][102]

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