Operative Planning

Review Imaging

• Computed tomography (CT) scan: low yield with respect to operative planning, unless patient has had a previous craniotomy, then might be helpful with understanding bone anatomy
  
• Magnetic resonance imaging (MRI)
  
  
  
  • Location
    
    
    
    • For brain stem cavernous malformation, T1 with thin slices to see if and where the lesion comes to the surface
    
    
  • Size and age of clot, if previous hemorrhage
    
  • Proximity to adjacent eloquent structures/nuclei and to the pial surface (in the case of brain stem cavernous malformation)
    
  • Presence of multiple lesions
    
  • Presence of venous angioma
    
  • Stereotactic sequences for use of frameless imaging guidance intraoperatively
  
  
• Angiogram
  
  
  
  • Only useful if an associated venous malformation or arteriovenous malformation (AVM) is suspected
    
  • Will rule out other vascular pathology, indicated in patients presenting with spontaneous intracerebral hemorrhage; this could change operative planning (i.e., presence of true AVM could lead to surgical management with radiosurgery)

Neurophysiology

Special Equipment for Operating Room

• As for acoustic neuroma

Operating Room Set-up

• Operating microscope
  
• Frameless stereotaxy

Anesthetic Issues

• Hyperventilation; optimize pCO₂ to 30 to 35 mm Hg
  
• Intravenous (IV) steroids (dexamethasone 10 mg IV or methylprednisolone 150 mg IV)
  
• Antibiotics (cefazolin 1 gm IV every 6 hours, oxacillin 2 gm every 6 hours, or vancomycin 1 gm every 12 hours); all antibiotics should be given at least 30 minutes prior to incision
  
• Diuresis with mannitol (0.5 to 1 g/kg) or mannitol + furosemide at time of skin incision
  
• Anticonvulsants continued if patient already on medications; not necessary in infratentorial lesions
  
• Blood pressure as per routine with any intracranial surgery
  
• If neurophysiology (SSEP, BAERs) is to be used, limitations to use of muscle relaxants and paralytics similar to acoustic neuroma

Preparation of Frameless Stereotaxy

• Load images onto system
  
• Perform patient coregistration
  
• Check accuracy of instruments and probes

Positioning

• Highly variable depending on location of lesion and approach used

Shave Patient

• Clip hair with electric razor, do not shave
  
• Approximately 3 cm width along length of incision

Incision, Craniotomy, Dural Opening

• Approaches
  
  
  
  • Suboccipital: midline cerebellar or cerebellar hemisphere lesions; transvermian modification for midline pontine lesions, consider velotelar approach
    
  • Infratentorial supracerebellar: collicular lesions
    
  • Occipital transtentorial
    
  • Retrosigmoid or presigmoid: lateral pontine lesions
    
  • Far lateral
    
  • Transtemporal
    
  • Frontotemporal/subtemporal transtentorial: lesions of the cerebral peduncle
    
  • Velotelar: fourth ventricle lesions
  
  
• Pial Incision

Resection of Lesion

• Dissection of glial plane
  
• Empty caverns within lesion of clot to internally debulk (internal decompression) then roll lesion on itself to resect away from glial plane

• Intensive care unit monitoring for at least 24 to 48 hours, rule out postoperative hydrocephalus
  
• Blood pressure: systolic control below 120 mm Hg (140 if patient with poorly controlled hypertension preoperative) for first 24 to 48 hours
  
• Antibiotics continued for 24 hours, longer if ventriculostomy catheter in place
  
• Steroids tapered slowly
  
• CT scan in 12 to 18 hours
  
• MRI eventually
  
• Sutures removed in 7 to 10 days