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Key Features

Essentials of Diagnosis

  • Fever, headache, altered mental status

  • Meningismus

  • Gram-positive diplococci on Gram stain of cerebrospinal fluid; counterimmunoelectrophoresis may be positive in partially treated cases

General Considerations

  • Streptococcus pneumoniae is the most common cause of meningitis in adults and the second most common cause of meningitis in children over the age of 6 years

  • Head trauma, with cerebrospinal fluid leaks, sinusitis, and pneumonia may precede it

  • Penicillin-resistant strains may cause meningitis

Demographics

  • Until 2000, S pneumoniae infections caused 100,000–135,000 hospitalizations for pneumonia, 6 million cases of otitis media, and 60,000 cases of invasive disease, including 3300 cases of meningitis

  • Disease figures are now changing due to conjugate vaccine introduction

Clinical Findings

Symptoms and Signs

  • Rapid onset, with fever, headache, and altered mentation

  • Pneumonia may be present

  • Compared with meningitis caused by the meningococcus

    • Pneumococcal meningitis lacks a rash

    • Obtundation, focal neurologic deficits, and cranial nerve palsies are more prominent features and may lead to long-term sequelae

Differential Diagnosis

  • Meningitis due to other causes, eg, meningococcus, Listeria, aseptic

  • Subarachnoid hemorrhage

  • Encephalitis

  • "Neighborhood reaction" causing abnormal cerebrospinal fluid, such as

    • Brain abscess

    • Epidural abscess

    • Vertebral osteomyelitis

    • Mastoiditis

    • Sinusitis

    • Brain tumor

  • Dural sinus thrombosis

  • Noninfectious meningeal irritation

    • Carcinomatous meningitis

    • Sarcoidosis

    • Systemic lupus erythematosus

    • Drugs (eg, nonsteroidal anti-inflammatory drugs, trimethoprim-sulfamethoxazole)

    • Pneumonia

    • Shigellosis

Diagnosis

Laboratory Tests

  • See Table 30–1

  • Cerebrospinal fluid

    • Typically has > 1000 white blood cells per microliter, over 60% of which are polymorphonuclear leukocytes

    • Glucose concentration is < 40 mg/dL (< 2.22 mmol/L), or < 50% of the simultaneous serum concentration

    • Protein usually exceeds 150 mg/dL (1500 mg/L)

    • Gram stain shows gram-positive cocci in up to 80–90% of cases

  • In untreated cases, blood or cerebrospinal fluid cultures are almost always positive

  • Fifty percent rate of bacteremia

  • Antigen detection tests may occasionally be helpful in establishing the diagnosis in the patient who has been partially treated and in whom cultures and stains are negative

Treatment

Medications

  • See Tables 30–5 and 30–2

  • Give antibiotics as soon as the diagnosis is suspected

  • If lumbar puncture must be delayed (eg, while awaiting results of an imaging study to exclude a mass lesion), ceftriaxone, 4 g intravenously, should be given after blood cultures (positive in 50% of cases) have been obtained

  • If gram-positive diplococci are present on the Gram stain, then vancomycin, 30 mg/kg/day intravenously in two divided doses, should be administered in addition to ceftriaxone until the isolate is confirmed not to be penicillin-resistant

  • Once susceptibility to penicillin has been confirmed, penicillin, 24 million units daily intravenously in six divided doses, or ceftriaxone, 4 g/day as a single dose or as two divided doses, is recommended

  • For severe penicillin ...

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