Operative Planning

• Imaging
  
  
  
  • Gadolinium-enhanced brain magnetic resonance imaging (MRI): determine lesion origin at tuberculum sella or cribriform plate; determine extent of disease affecting optic nerve, optic chiasm, optic canal, orbit, cavernous sinus, internal carotid artery, anterior cerebral artery (ACA) branches, and extracranial sinus involvement
    
  • Computed tomography (CT): evaluate for hyperostosis or erosion
    
  • Location of optic nerves and chiasm are inferolateral to olfactory groove meningiomas and superolateral to tuberculum sellae tumors
    
  • Consider preoperative angiography and possible embolization
    
  • Acquire preoperative gadolinium-enhanced MRI scan for intraoperative image guidance
  
  
• Extent of resection
  
  
  
  • Extent of resection based on Simpson grade correlates with recurrence of disease
    
  • Postoperative radiation therapy significantly decreases recurrence and progression; sub-total resection followed by radiation therapy is advocated if complete resection carries the risk of significant morbidity
  
  
• Neuro-ophthalmology
  
  
  
  • Preoperative evaluation to document existence of visual field and cranial nerve deficits
  
  
• Endocrine evaluation to identify endocrinopathies

Routine Equipment

• Lumbar drain set-up
  
• Major craniotomy tray
  
• Microsurgery tray
  
• Mayfield head holder
  
• High-speed drill
  
• Operating microscope
  
• Fibrin glue

• Image guidance system
  
• Leyla bar or Greenberg system for self retaining retractors
  
• Tarsorrhaphy set-up

Operating Room Set-up

• Headlights
  
• Loupes
  
• Bipolar and monopolar cautery
  
• Image guidance equipment

Anesthetic Issues

• Antibiotics: cefazolin, 2 g intravenous (IV) at least 30 minutes prior to incision and then every 4 hours; or vancomycin, 1 g IV 30 minutes prior to incision and then every 12 hours
  
• Dexamethasone (10 mg IV) preoperative
  
• Antiepileptic medication: phenytoin, 15 mg/kg IV during surgery to achieve therapeutic level
  
• Mannitol: 1 g/kg IV at incision
  
• Precordial Doppler to monitor for air embolism (superior sagittal sinus exposed with bifrontal craniotomy)
  
• Potential exists for high volume of blood loss (1 liter or more)
  
• Arterial line and either good peripheral venous or central venous access

Spinal Drain

• Five to 10 mL of cerebrospinal fluid are removed periodically to facilitate brain relaxation and reduce excessive frontal lobe retraction.

Positioning

• After intubation, the patient is placed in a lateral decubitus position for lumbar drain insertion. The patient is then positioned supine. The neck is slightly extended. The head is placed on a horseshoe headrest or pinned in a Mayfield head holder if self retaining retractors or image guidance is utilized for resection of intracranial disease.

Tarsorrhaphies

• Performed bilaterally

Preparation of Operative Fields

Bifrontal Craniotomy

• Bilateral Sutar-type incision; the scalp and galea are reflected anteriorly; the pericranium is isolated as a separate flap; the pericranium is incised behind the scalp incision to maximize the size of this flap and it is reflected anteriorly. Care must be taken to ensure the pericranium remains in one piece and is well vascularized. The periorbita is reflected from the orbits. At this time the ethmoidal arteries are coagulated and divided for olfactory groove meningiomas. Temporalis muscle is reflected inferiorly and the supraorbital neurovascular bundles are reflected from their foramina or notches.
  
• Bifrontal craniotomy is then performed. This craniotomy should extend from one superior temporal line to the other. Dura is reflected from the floor of the anterior cranial fossa.
  
• Nasal, ethmoid, and orbital osteotomies are performed to remove the supraorbital bar.
  
• Frontal sinus exenteration is performed.

Dural Opening

• Dura is opened across the frontal poles. The superior sagittal sinus and falx are divided above the crista galli after suture ligation of the sinus.
  
• With tuberculum sellae lesions, the olfactory tracts are dissected using the operating microscope and preserved.