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
• Digital subtraction myelography (DSM):
  • Gold standard for diagnosis
  • Dynamic imaging allows visualisation of contrast extravasation
• MR myelography:
  • Heavily T2-weighted sequences
  • May show CSF leak site or fistula tract
• CT-guided paraspinal venography:
  • Useful for confirming and localising fistulas

Treatment

• Conservative management:
  • Bed rest
  • Hydration
  • Caffeine intake
• Epidural blood patch:
  • First-line interventional treatment
  • May require multiple attempts or targeted patches
• Surgical repair:
  • Direct closure of fistula
  • Indicated when conservative measures fail
• Minimally invasive techniques:
  • CT-guided fibrin glue injection
  • Endovascular embolisation of fistula
• Post-treatment imaging:
  • To confirm fistula closure and resolution of intracranial hypotension signs

Differential diagnosis