Background Bacterial meningitis in older adults is a well-studied and serious disease, but few studies have investigated the epidemiology and outcomes of community-acquired meningitis in older adults. Methods We conducted a retrospective study of 619 adults in Houston, Texas, with community-acquired meningitis hospitalized between January 1, 2005, and January 1, 2010. Patients were categorized as older if age ≥65 (N=54) and younger if age 18–64 (N=565). An adverse clinical outcome was defined as a Glasgow Outcome Scale score of 4 or less. Results Older patients consisted of 8.7% (54/619) of the total cohort and had higher rates of comorbidities, abnormal neurological and laboratory findings, abnormalities on computed tomography and magnetic resonance imaging of the head and adverse clinical outcomes (ACO) (p<0.05). The majority of patients (65.8%) had meningitis of unknown etiology. Bacterial meningitis was an infrequent cause (7.4%). Of the known causes, bacterial meningitis and West Nile virus were more common in older patients. In contrast, younger patients more frequently had cryptococcal and viral meningitis. On logistic regression, female gender was predictive of a poor outcome in the older patients, whereas abnormal neurologic exam, fever, and CSF glucose <45mg/dLwere significant poor prognostic factors in younger patients (p<0.05). Conclusion Most cases of community-acquired meningitis are of unknown origin. Older patients are more likely to have bacterial meningitis and West Nile virus infection when a cause can be identified. They also have more neurologic abnormalities, laboratory and imaging abnormalities, as well as adverse clinical outcomes.

Study objectives Hypoglycorrhachia (CSF glucose < 45mg/dL) has been identified as a prognostic factor in patients with meningitis. We analyzed the differential diagnosis of hypoglycorrhachia and its clinical significance. Methods Retrospective study of 620 adult patients with community acquired meningitis [CSF WBC >5 cells/mm3, absence of a CSF shunt or recent neurosurgical procedure (< 1 month)] at 8 Memorial Hermann Hospitals in Houston, TX from January, 2005 to December, 2010. An adverse clinical outcome was defined as a Glasgow outcome scale of 4 or less. Results Out of 620 patients with meningitis, 116 (19%) had hypoglycorrachia. Etiologies of hypoglycorrhachia were idiopathic (40), bacterial (27), cryptococcal (26), viral (15), and tuberculous (4). Patients with hypoglycorrachia were more likely to be immunosuppressed, have a history of intravenous drug use, and present with a vesicular or petechial rash, nausea or vomiting, nuchal rigidity, sinusitis/otitis, abnormal mental status and focal neurological deficits compared to those patients without hypoglycorrachia (p<0.05). Additionally, patients in the hypoglycorrhachia group had significantly higher rates of positive CSF and blood cultures, urgent treatable conditions and abnormal cranial imaging (p<005). Furthermore, patients with hypoglycorrachia had more adverse clinical outcomes [26 out of 116 (22.4%) vs. 45 out of 504 (8.9%)] (p< 0.001). Conclusion Hypoglycorrhachia has significant clinical and prognostic value in the evaluation of adult patients with community-acquired meningitis.

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Background We aimed to derive and validate a risk score that identifies adults with cerebrospinal fluid (CSF) pleocytosis and a negative CSF Gram stain at low risk for an urgent treatable cause. Methods Patients with CSF pleocytosis and a negative CSF Gram stain were stratified into a prospective derivation (n=193) and a retrospective validation (n=567) cohort. Clinically related baseline characteristics were grouped into three composite variables, each independently associated with a set of predefined urgent treatable causes. We subsequently derived a risk score classifying patients into low (0 composite variables present) or high ( ≥ 1 composite variables present) risk for an urgent treatable cause. The sensitivity of the risk score was determined in the validation cohort and in a prospective case series of 214 adults with CSF-culture proven bacterial meningitis, CSF pleocytosis and a negative Gram stain. Findings A total of 41 of 193 patients (21%) in the derivation cohort and 71 of 567 (13%) in the validation cohort had an urgent treatable cause. Sensitivity of the dichotomized risk score to detect an urgent treatable cause was 100.0% (95%CI 93.9-100.0%) in the validation cohort and 100.0% (95%CI 97.8-100.0%) in bacterial meningitis patients. Interpretation The risk score can be used to identify adults with CSF pleocytosis and a negative CSF Gram stain at low risk for an urgent treatable cause.

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