Operative Planning

• Review imaging
  
  
  
  
  • Computed tomography (CT)
    
    
    
    • Severity of subarachnoid hemorrhage may indicate the degree of brain edema
      
    • Presence of temporal lobe hematoma may indicate projection above the tentorial edge
      
    • Presence and degree of hydrocephalus may indicate need for ventricular drain
      
    • Location and size of the frontal sinus affect the design of the bone flap
    
    
  • Computed tomography angiogram
    
    
    
    • Demonstrates the sac size, presence of lobulations or daughter sacs, neck width
      
    • Demonstrates dome projection lateral, posterior, or medial
      
    • Location of the posterior communicator in relationship to the sac; presence or absence of an ipsilateral P1 segment to suggest a fetal or near fetal PCOM artery circulation pattern
      
    • Presence of calcification/atherosclerosis within the neck/dome of the aneurysm
      
    • Presence of additional aneurysms ipsilateral to the posterior communicator
    
    
  • Digital subtraction cerebral angiogram (DSA)
    
    
    
    • Indicates the size, dome projection, aneurysm morphology with presence of daughter sacs, neck size
      
    • Presence of fetal or near fetal circulation pattern
      
    • Location of the anterior choroidal artery in relation to aneurysm neck
      
    • Important to differentiate angiographically between PCOM artery aneurysm and superior hypophyseal artery aneurysm (proximal control may be more difficult in the latter; thus, consider prepping the extracranial carotid in the neck)
      
    • Presence of additional aneurysms ipsilateral to the posterior communicator

• Tapered teardrop occluder suckers (Fukushima [PMT Corporation, Chanhassen, MN] type)
  
• Aneurysm clips, standard and fenestrated (Aesculap titanium)
  
• Temporary aneurysm clips
  
• Rhoton dissectors
  
• Bipolar and Bovie electrocautery
  
• Arachnoid knife (no. 10 Beaver blade)
  
• Intraoperative micro-Doppler
  
• Electroencephalogram/somatosensory evoked potential/motor evoked potential monitoring
  
• Intraoperative angiography (particularly with large complex aneurysms with fetal circulation anatomic configuration by angiogram)

Operating Room Set-up

• Operating microscope: mouthpiece for small focus adjustments during dissection; if observer head is used, consider the relationship of the microscope and the scrub nurse and the assistant to minimize interference
  
• Electric operating room table

Anesthetic Issues

• Mild hyperventilation, pCO₂ to 30 to 32 mm Hg
  
• Intravenous (IV) dexamethasone (10 mg) prior to incision
  
• IV oxacillin 2 gm IV every 6 hours (alternatively vancomycin 1 gm IV every 12 hours) administered 30 minutes prior to incision
  
• IV mannitol 0.5 to 1 gm administered at the time of the skin incision for brain relaxation (consider lower dose in unruptured cases to avoid volume depletion)
  
• Continue anticonvulsants if started presurgery (loading in the operating room is not routine but based on clinical circumstances)
  
• Careful monitoring of blood pressure at the time of Mayfield head holder placement
  
• For patients with subarachnoidal hemorrhage (SAH) and no spasm or unruptured cases, systolic blood pressure is maintained at 120 to 140 mm Hg during the procedure
  
• Slightly increased pressure for patients at risk for or with evidence of vasospasm and for periods of temporary occlusion
  
• Routine placement of arterial line and Foley catheter
  
• Central line access for ruptured aneurysms or complex cases
  
• Anticipation of the pharmacological need for burst suppression in the setting of premature aneurysmal rupture or for routine temporary occlusion

External Ventricular Drain

Positioning

• The patient is supine with the head fixed in the Mayfield head holder, single pin in the contralateral frontal region, two pins in the occipital area, 60 to 80 pounds of pressure
  
• The head is rotated 20 to 30 degrees to the contralateral side and the neck is extended 10 to 15 degrees (rotation of the head > 30 degrees brings the temporal lobe more into the field and may necessitate temporal lobe retraction)

Pterional Craniotomy

Initial Dissection

• Goal: proximal control of the internal carotid artery (ICA)
  
• Steps
  
  
  
  • Assemble and position self retaining retractor arm in anticipation of frontal lobe retraction
    
  • Line the frontal lobe superior to the sylvian fissure with protective nonstick pledgets (Adaptic [Johnson & Johnson, New Brunswick, NJ] or Telfa)
    
  • Under the operative microscope, with one hand controlling the regulated suction and the other manipulating the retractor, gently and gradually advance the retractor to elevate the frontal lobe, identifying the optic nerve
    
  • Release with sharp dissection the arachnoid bands tethering the optic nerve to the frontal lobe using a no. 10 Beaver blade, a Rhoton no. 6 dissector, and fine bayoneted scissors
    
  • Dissect laterally into the opticocarotid triangle medial to the carotid, releasing cerebrospinal fluid (CSF). Clear a space for the medial blade of a temporary clip.
    
  • Dissect the arachnoid layer laterally over the carotid proximal to the posterior communicator for the lateral blade of the temporary clip

Initial Exposure of the Aneurysm Neck

Full Identification of the Relevant Anatomy Prior to Clipping