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  • Updated 02.08.2024
  • Released 04.04.1995
  • Expires For CME 02.08.2027

Intracranial subdural empyema



Intracranial subdural empyema represents infection arising in the cleavage plane between the cranial dura mater and the subjacent layer of the meninges, the arachnoid. Although the condition is traditionally associated with sinusitis or otitis, it may also occur as a complication of other cranial or dental infections, neurosurgical procedures, or cranial trauma. Intracranial subdural empyema represents one of the most urgently dangerous of all intracranial processes because it can spread rapidly to cover an entire cerebral hemisphere or much of the posterior fossa, producing a rapidly expanding, potentially fatal mass lesion. In this article, the author reviews the pathogenesis, clinical features, diagnosis, and treatment of this disorder.

Key points

• Intracranial subdural empyema represents loculated infection in the potential space between the outer layer of the meninges, the dura, and the arachnoid. This potential space encompasses a large intracranial area in which infection can rapidly spread to cover, and compress, an entire hemisphere or much of the posterior fossa.

• The condition is most commonly a complication of sinusitis or otitis, particularly in males in later childhood, adolescence, or early adulthood. Less frequently, intracranial subdural empyema may also occur as a complication of dental infections, neurosurgical procedures, or trauma. The condition may be preceded by intracranial epidural abscess.

• Subdural empyema is a neurologic and neurosurgical emergency, which should be suspected in any febrile patient with rapidly developing signs indicating involvement of an entire cerebral hemisphere.

• MRI with gadolinium enhancement is the diagnostic procedure of choice. Contrast-enhanced CT scan may be used if MRI is not available but is less sensitive.

• Treatment of intracranial subdural empyema almost always involves surgical drainage with adjunctive antibiotic therapy.

• Occasionally, subdural empyemas may be identified by MRI at a time when they are too small to allow surgical drainage. In such cases, the empyema is treated with antibiotics alone, with close follow-up by MRI or CT to make certain that the empyema is not enlarging, which would require neurosurgical intervention.

Historical note and terminology

The fact that ear infections could progress to delirium and death was known to ancient writers including Hippocrates (105), but the association of this process with intracranial extension of infection was not understood. Although a case suggestive of subdural empyema was described by Richter in 1773 (22), recognition of subdural empyema as a distinct clinical and pathological entity did not occur until the mid-19th century (22; 54). Major case series in the past century included those of Kubik and Adams, Courville, and Schiller and colleagues (21; 22; 54; 87). Early terms for the condition included "pachymeningitis interna" (to distinguish the entity from epidural abscess, termed "pachymeningitis externa") and "purulent pachymeningitis." Association of intracranial subdural empyema with sinus and ear infections came through case series published in the late 19th and early 20th centuries (21; 22; 54).

Subdural empyema was initially purely a clinical diagnosis, and its rapid progression and malignant course were such that Le Beau termed intracranial subdural empyema "the most imperative of all neurosurgical emergencies" (55). Before the advent of MRI, diagnosis of subdural empyema was made by burr holes, angiography, or, beginning in the mid-1970s, CT. Treatment was invariably surgical, with antibiotics being assigned an adjunctive but not curative role. The introduction of MRI, however, has provided a rapid, noninvasive method for diagnosing and following subdural empyemas and can identify empyemas too small to require surgery (103; 91; 53; 79). With the widespread use of CT and then MRI, mortality from subdural empyema has fallen, and it has become possible (in occasional, carefully selected cases) to treat a subdural empyema with antibiotic therapy alone (67; 60; 78; 32).

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