Imaging

• Evaluation of all aneurysms begins with appropriate imaging
  
• Computed tomography (CT) imaging
  
  
  
  • Imaging of the parenchyma and vasculature (CT angiography) gives information about the degree of subarachnoid hemorrhage, calcification of aneurysm dome, parent and branch vessels and can create excellent three-dimensional (3D) imaging of most aneurysms. In addition, the relationship of aneurysms to various structures can be characterized (i.e., anterior or posterior clinoid).
  
  
• Magnetic resonance imaging (MRI)
  
  
  
  • MRI/MR angiography is a useful tool in diagnosis and localization of distal aneurysms particularly if image guidance is to be used as a surgical aid.
  
  
• Angiography
  
  
  
  • Remains standard modality of vascular imaging when combined with 3D angiography. Gives information about the morphology, location, and helps guide treatment alternatives; 3D imaging helps guide vessel reconstruction and treatment.

Timing of Surgery

• Early in favorable Hunt-Hess grades
  
• Delayed surgery in poor grade patients, except when associated with large parenchymal hematoma

Special Equipment

• Image guidance: when necessary to localize lesion
  
• Intraoperative angiography in select cases
  
• Doppler used to confirm patency of surrounding vessels

Anesthetic Issues

• Gentle hyperventilation
  
• Adequate brain relaxation is crucial (mannitol, furosemide)
  
• Preparation for burst suppression for cerebral protection
  
• Possible ventricular drainage to aid in brain relaxation

Intraoperative

Positioning

• Supine with neck flexed for bicoronal incision
  
• Supine with neck turned for pterional incision

• Infracallosal location: pterional or low bifrontal craniotomy
  
• Genu or anterior supracallosal location: right frontal parasagittal craniotomy
  
  
  
  • Bicoronal scalp flap anterior to coronal suture
  
  
• Posterior supracallosal location: right frontal parasagittal craniotomy
  
  
  
  • Horseshoe scalp flap over coronal suture
  
  
• Rectangular craniotomy crossing midline and exposing the lateral aspect of the sagittal sinus
  
• Horseshoe dural opening
  
• Identify corpus callosum
  
  
  
  • Transversely running, parallel white fibers
    
  • Approximately 1 cm deep to the free edge of the falx

Aneurysm Dissection and Clipping

• Thorough dissection of bilateral pericallosal arteries
  
• Temporary clip frequently difficult to place secondary to narrow exposure
  
• In event of intraoperative rupture bleeding should be inhibited with temporary clips

Postoperative

• Distal anterior cerebral artery (ACA) infarction: contralateral leg monoparesis, hemiparesis, contralateral sensory loss, visual agnosia and apraxia, incontinence
  
• Supplementary motor area syndrome (excellent recovery potential)