Intracranial subdural empyema

Introduction
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By John E Greenlee MD

Intracranial subdural empyema is also known as or subsumes Pachymeningitis interna, Purulent pachymeningitis, and Subdural abscess. -ed.

Intracranial subdural empyema represents infection arising in the cleavage plane between the cranial dura mater and the arachnoid. Although the condition is most frequently associated with sinusitis, it may also occur as a complication of otitis, other cranial or dental infections, neurosurgical procedures, or cranial trauma. Intracranial subdural empyema represents one of the most 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 review, Dr. John Greenlee, Professor of Neurology at the University of Utah School of Medicine and staff neurologist at the George E Wahlen Veterans Affairs Medical Center in Salt Lake City, Utah, 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 area encompasses a large potential space 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. The condition may be preceded by epidural abscess.
  • Subdural empyema 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.
  • Intracranial subdural empyema is usually a neurosurgical emergency. Occasionally, early empyemas may be too small to drain and may be treated with antibiotics alone, with close MRI follow-up.