Brain abscess is an important complication of both systemic and pericranial infections (sinusitis, otitis, etc.), of cranial trauma, and of neurosurgical procedures. The disorder is highly treatable – at times with antibiotics alone – if diagnosed early in its course. If misdiagnosed, however, it may cause severe neurologic injury or death. In this article, the author discusses the pathogenesis and clinical presentation of brain abscess and provides an approach to diagnosis and treatment of the disorder.
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• Brain abscess most commonly arises by hematogenous spread. Less frequently, it may occur as a complication of sinusitis, otitis, mastoiditis, or penetrating trauma. Brain abscess may be caused by a single agent, but in a minority of cases, it may also be polymicrobial.
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• The classic presentation of brain abscess is headache, fever, and focal neurologic signs. In most patients, however, this triad is not found, and presentation is that of a subacutely developing intracerebral mass lesion. Rapid deterioration may follow intraventricular rupture.
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• The diagnostic procedure of choice for brain abscess is contrast-enhanced MRI. CT scan with contrast, although useful, is less sensitive.
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• Treatment of brain abscess, in the great majority of patients, consists of antibiotic therapy and surgical drainage. Until identification of the causative organism(s), initial antibiotic therapy should be directed against Staphylococcus aureus and other potential Gram-positive agents, Gram-negative agents, and anaerobes.
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• Occasionally, small abscesses may respond to antibiotics alone. Patients being treated with antibiotics alone, however, need to be followed carefully by clinical examination and MRI to detect enlargement of the abscess in the face of antibiotic treatment.
Historical note and terminology
The notion that ear infections could progress to delirium and death, a series of clinical events consistent with brain abscess as well as subdural empyema or septic venous thrombophlebitis, was known to ancient writers, including Hippocrates (51). Morand, in the 16th century, is the first individual credited with successful drainage of a brain abscess. Methodical development of surgical approaches to brain abscess, however, did not begin until the latter part of the 19th century (13). Beginning at this same time, development of effective surgical treatment of chronic otitis, a major cause of purulent intracranial infections, caused a fall in the incidence of otogenic brain abscess long before the advent of antibiotics.
Prior to CT, diagnosis of brain abscess remained elusive, with treatment ultimately surgical; antibiotics were assigned an adjunctive, but not usually curative, role. Since the late 1970s, however, the introduction of CT and subsequently MRI has allowed rapid, noninvasive methods for diagnosing and monitoring brain abscess (30; 29; 41; 111; 10; 99). With the widespread use of these neuroimaging techniques, mortality from brain abscess has fallen, and it has become possible to treat a portion of brain abscesses with antibiotic therapy alone (74; 44; 99; 14), or to drain abscesses using stereotactic, CT-, or MR-guided needle aspiration (61; 69; 54; 42; 04; 99; 14; 27).