Operative Planning

• Review imaging (computed tomography, magnetic resonance imaging, magnetic resonance angiography, and/or angiogram)
  
• Spinal drain

Equipment

• Major craniotomy tray
  
• Mayfield head holder
  
• High-speed drill
  
• Leyla bar and Greenberg retractors
  
• Frameless stereotaxic equipment

Operating Room Set-up

• Headlight
  
• Loupes
  
• Bipolar cautery and Bovie cautery
  
• Cavitron ultrasound aspirator (Integra)
  
• Microscope
  
• Spinal drain insertion

Anesthetic Issues

Subtemporal Transtentorial Approach

• A horseshoe skin incision is made starting from the zygoma 1 cm anterior to the tragus, extending above the pinna, and curving down ~2 cm behind the mastoid
  
• The scalp flap is reflected inferiorly down to the zygoma; care should be taken not to enter the external auditory canal
  
• Towel clips are placed at the base of the flap and secured to the Leyla bar with rubber bands for flap retraction

Burr Hole

• A single burr hole is made in the squamous portion of the temporal bone immediately above the root of the zygoma

Craniotomy

• A temporal craniotomy is made with its posterior extent just above the mastoid; additional bone is removed down to the middle fossa floor. The transverse sinus is freed and additional craniotomy is performed infratentorially if necessary.
  
• Mastoid air cells are generously waxed
  
• Holes are drilled for epidural tenting sutures

Extradural Dissection

• This is performed from a lateral to medial and posterior to anterior direction to avoid stretching the greater superficial petrosal nerve (GSPN) branch of the facial nerve.
  
• The following landmarks are identified:
  
  
  
  • Tegmen tympani
    
  • Arcuate eminence
    
  • Lesser superficial petrosal nerve (LSPN)
    
  • GSPN, middle meningeal artery
    
  • Mandibular branch of the trigeminal nerve
    
    
    
    • The LSPN can be distinguished from the GSPN because it joins the middle meningeal artery at the foramen spinosum

Dural Opening

• The dura is opened with a T-shaped incision along the inferior temporal lobe and with the vertical limb along the middle fossa floor

• Retraction of temporal lobe is performed with the aid of the operating microscope using the advancement of Bicol, Greenberg retractor blades, and Cottonoids, as in the standard subtemporal approach
  
• CN IV is identified; the division of the tentorium begins immediately posterior, a couple of millimeters off the petrous ridge
  
• The tentorial division is extended 3 to 4 cm posterolaterally and a couple of millimeters posterior to the superior petrosal sinus without injuring the sigmoid sinus. The division of the tentorium is carried in an anterolateral direction into the middle fossa and across the superior petrosal sinus with suture ligatures or titanium clips, resulting in an excised triangular flap of tentorium and a view down onto the clivus.
  
• Depending on the location of the lesion, additional bone removal of the posterior clinoids and/or petrous apex is performed if needed

Closure

• Dura closed with 4–0 silk sutures
  
• Central dural tenting sutures are placed and the dura is covered with dural substitute duraplasty (Duraform/Duragen)
  
• The bone flap is replaced and secured with titanium microplates
  
• The temporalis fascia is approximated with 2–0 Vicryl
  
• The galea is closed with inverted 3–0 Vicryl sutures
  
• The skin is closed with staples and Xeroform and head wrap applied

• Steroid taper begins on postoperative day 1
  
• Antibiotics continued for 24 hours