![]() Potential causes include early presentation, recent prior antimicrobial therapy, and neutropenia. Why some patients have milder CSF abnormalities cannot usually be identified. For example, in a prospective study of 1412 adults with bacterial meningitis, a CSF WBC >1000/microL was seen in only 66 percent of patients. The spectrum of CSF values in bacterial meningitis is so wide, however, that the absence of one or more of the typical findings is of little value. The most common clinical features include a severe headache (84 percent), fever greater than 38☌ (74 percent), stiff neck (74 percent), a Glasgow Coma scale 200 mg/dL (>2000 mg/L), and a WBC count above 1000/microL, with a percentage of neutrophils usually greater than 80 percent. Older patients (age >60 years) more commonly present with the triad than younger patients (58 versus 36 percent). Presenting manifestations - The classic triad of acute bacterial meningitis, which occurs in 41 percent of patients, consists of fever, nuchal rigidity, and a change in mental status, usually of sudden onset. ![]() (See "Initial therapy and prognosis of bacterial meningitis in adults", section on 'Avoidance of delay'.) Any form of bacterial meningitis that is untreated or treated very late in its course is almost uniformly fatal. ĭeterminants of the pace of bacterial meningitis are related to both host and microbial virulence factors. In the largest prospective study of 1412 episodes of bacterial meningitis, for example, approximately half of the patients presented less than 24 hours after onset of illness. (See "Epidemiology of bacterial meningitis in adults".)ĬLINICAL FEATURES - Patients with bacterial meningitis are usually quite ill and often present soon after symptom onset. Ī more detailed discussion of the epidemiology of and risk factors for bacterial meningitis is presented elsewhere. The major causes of health care-associated ventriculitis and meningitis are different (usually staphylococci and aerobic gram-negative bacilli) and occur more commonly after neurosurgical procedures (eg, post-craniotomy, ventriculoperitoneal shunts, lumbar shunts, external ventricular drains or following head trauma such as basilar skull fracture with or without clinical evidence of leak of cerebrospinal fluid).The major causes of community-acquired bacterial meningitis in adults in developed countries are Streptococcus pneumoniae, Neisseria meningitidis, and, primarily in patients over 50 years of age or those who have deficiencies in cell-mediated immunity, Listeria monocytogenes ( table 1).(See "Pathogenesis and pathophysiology of bacterial meningitis" and "Epidemiology of bacterial meningitis in adults" and "Initial therapy and prognosis of bacterial meningitis in adults" and "Treatment of bacterial meningitis caused by specific pathogens in adults" and "Bacterial meningitis in children older than one month: Clinical features and diagnosis" and "Bacterial meningitis in children older than one month: Treatment and prognosis" and "Approach to the patient with chronic meningitis" and "Approach to the adult with recurrent infections", section on 'Meningitis' and "Aseptic meningitis in adults".)ĮPIDEMIOLOGY - Bacterial meningitis can be community acquired or health care associated. The pathogenesis, epidemiology, treatment, prognosis, and prevention of acute bacterial meningitis in adults and issues related to acute bacterial meningitis in children and to chronic, recurrent, and aseptic meningitis are discussed separately. The clinical and laboratory features of acute bacterial meningitis in adults will be reviewed here. Bacterial meningitis reflects infection of the arachnoid mater and the CSF in both the subarachnoid space and the cerebral ventricles. ![]() The meninges consist of three parts: the pia, arachnoid, and dura maters ( figure 1). INTRODUCTION - Meningitis is an inflammatory disease of the leptomeninges, the tissues surrounding the brain and spinal cord, and is characterized by an abnormal number of white blood cells (WBCs) in the cerebrospinal fluid (CSF) in the majority of patients.
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