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Key Features

Essentials of Diagnosis

  • Symptoms and signs of expanding intracranial mass

  • There may be signs of a primary infection or of congenital heart disease

  • Fever may be absent

General Considerations

  • Presents as an intracranial space-occupying lesion

  • May occur as a sequela of ear or sinus infection, a complication of infection elsewhere in the body, or an infection introduced intracranially by trauma or surgical procedures

  • Most common infective organisms

    • Streptococci

    • Staphylococci

    • Anaerobes

  • Mixed infections also occur

Clinical Findings

Symptoms and Signs

  • Early symptoms

    • Headache

    • Drowsiness

    • Inattention

    • Confusion

    • Seizures

  • Later signs

    • Increasing intracranial pressure

    • Focal neurologic deficits

  • There may be little or no systemic evidence of infection

Differential Diagnosis

  • Other rapidly expanding intracranial space-occupying lesions

Diagnosis

Laboratory Tests

  • Examination of the cerebrospinal fluid does not help in diagnosis and lumbar puncture may precipitate herniation

  • Peripheral leukocytosis sometimes present

Imaging Studies

  • CT scan of the head characteristically shows an area of contrast enhancement surrounding a low-density core (similar to metastatic neoplasms)

  • MRI permits earlier recognition of focal cerebritis or abscess

Diagnostic Procedures

  • Stereotactic needle aspiration may enable a specific etiologic organism to be identified

Treatment

Medications

  • Intravenous antibiotics, combined with surgical drainage (aspiration or excision) if necessary to reduce the mass effect, or to establish the diagnosis

  • Broad-spectrum antibiotics are used if the infecting organism is unknown (Table 30–5)

  • Initial empiric antibiotic regimens typically include

    • Ceftriaxone, 2 g intravenously every 12 hours

    • Metronidazole, 15 mg/kg intravenous loading dose, followed by 7.5 mg/kg intravenously every 6 hours

    • Vancomycin, 1 g intravenously every 12 hours

  • Antimicrobial treatment is usually continued parenterally for 6–8 weeks and is followed by oral treatment for certain infections, such as nocardiosis, actinomycosis, fungal infections, and tuberculosis

  • Dexamethasone (4–25 mg orally four times daily, depending on severity, followed by tapering of dose, depending on response) may reduce any associated edema; intravenous mannitol is sometimes required

Table 30–5.Examples of initial antimicrobial therapy for acutely ill, hospitalized adults pending identification of causative organism (in alphabetical order).

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