Operative Planning

Monitoring

• No clear evidence exists to justify the use of intraoperative cranial nerve monitoring

Positioning

• Place lumbar drain and keep clamped
  
• Mayfield head holder placed in anteroposterior position
  
• Head turned so that posterior fossa and occiput are accessible
  
• Shave the hair overlying the region
  
• Shoulder roll under ipsilateral shoulder
  
• Pneumatic compression device placed
  
• Note: positioning for posterior fossa lesions MUST allow for access to BOTH the occipital and suboccipital regions
  
• Note: positioning for cavernous fistulae MUST allow for extradural and intradural approaches (please refer to the Dolenc and cavernous sinus approaches)

Sterile Scrub

• Betadine detergent scrub for all areas
  
• Pat dry with sterile towel

Mark Incisions

• For the posterior fossa, incisions require that the entire dural sinus harboring the fistula be exposed. In the case of the lateral sinus (transverse and sigmoid sinus complex, a common site for a fistula), exposure will be from mastoid to torcular.
  
• Reverse horseshoe incision

Prep and Drape

• Prep with Betadine (allow to dry completely)
  
• Drape with four blue towels

Incision/Exposure

Craniotomy

• Wide exposure of the fistula is required and thus must extend above and below the sinus
  
• Craniotome should be used for the craniotomy but great care is required over the sinus to prevent a potentially fatal hemorrhage
  
• Identify the boundaries of the sinus with careful bony resection along the asterion with a round burr prior to proceeding to craniotomy
  
• Frequent use of bone wax is needed to minimize blood loss
  
• Mild hypotension required at this juncture given the degree of transosseous drainage that is common in these fistulae; prepare to transfuse at the time the bone flap is elevated
  
• Place Gelfoam and FloSeal over sinus to help mark sinus and help provide hemostasis
  
• Mild pressure with a Cottonoid and rigorous, organized bipolar coagulation of the dura is required to achieve adequate hemostasis
  
• Dural tacking sutures are placed
  
• Bone wax the mastoid air cells
  
• Open dura parallel to the lateral sinus above the sinus
  
• Open dura parallel to the lateral sinus below the sinus
  
• Withdraw cerebrospinal fluid via the lumbar drain
  
• Expose, identify, and ligate (cauterize) the occipital and cerebellar veins entering the dura; confirm these findings on preoperative angiogram

Technique

• Place hemostats across the sinus and tentorium on either side of the fistulous site
  
• Divide the sinus and oversew with nonabsorbable 3–0 suture (magnetic resonance compatible clips might be considered but sutures are preferred)
  
• Retract the lateral portion of the sinus to identify the tentorium
  
• Methodically cauterize and incise the tentorium progressively toward the petrous ridge
  
• Again, excessive bleeding from the tentorial sinuses might be encountered and might require hemostatic clips at this point
  
• Identify arterial contribution from the petrous region and obtain hemostasis with cautery or bone wax (if transosseous arteries are identified)
  
• Fulguration of the petrous dura and possible resection of the bony margin of the lateral portion of the petrous bone may be required to obliterate the dural fistula
  
• Resect the occipital and cerebellar dura that has been isolated during the dissection
  
• Pack the distal sigmoid sinus with oxidized cellulose

Alternative

Dural Repair/Closure

• Sew a dural patch along the entire defect for a watertight closure
  
• Supplement with DuraSeal (Confluent Surgical, Waltham, MA)
  
• Bone wax to the mastoid cells once again
  
• Secure the craniotomy flap with discs or miniplates and screws
  
• Copious irrigation
  
• Reapproximate muscle and fascial layer with 2–0 Vicryl suture
  
• Reapproximate skin with 3–0 Vicryl suture
  
• Staples for skin closure
  
• Dry sterile wrap
  
• Remove lumbar drain