CSF-venous fistula¶

Pathophysiology¶

• Direct connection between CSF and venous compartments
  • Often at nerve root sleeve level
  • Can occur at spinal or skull base level
• Results in CSF leakage and intracranial hypotension
• Proposed mechanisms:
  • Congenital weakness in dura mater
  • Trauma or iatrogenic causes
  • Degenerative changes in spinal structures

Demographics¶

• More common in middle-aged adults (40-60 years)
• Slight female predominance
• Associated conditions:
  • Connective tissue disorders (e.g., Ehlers-Danlos syndrome)
  • History of spinal surgery or intervention

Diagnosis¶

• Clinical presentation:
  • Orthostatic headache
  • Neck pain or stiffness
  • Tinnitus
  • Visual disturbances
• Cerebrospinal fluid analysis:
  • Often normal or shows mildly low opening pressure
  • May have slightly elevated protein levels
• High clinical suspicion required due to subtle nature of fistulas

Imaging¶

• Conventional MRI:
  • Brain: pachymeningeal enhancement, subdural collections, pituitary enlargement
  • Spine: may show extradural fluid collections
• CT myelography:
  • Limited sensitivity for small fistulas
• Lateral decubitus digital subtraction myelography or dynamic CT myelography is the key test, imaging the dependent side
  • The "hyperdense paraspinal vein sign" (early opacification of a paraspinal vein) localises the fistula
• Routine spine MRI is typically normal (no extradural fluid), which distinguishes a fistula from a dural CSF leak

Treatment¶

• Unlike a dural leak, a CSF-venous fistula responds poorly to blood patching
• Definitive treatment is transvenous embolisation or surgical ligation of the draining vein

Differential diagnosis¶