Operative Planning

• There is substantial debate in the literature regarding indications and goals of neurosurgical intervention for patients with brain stem gliomas
  
• Review imaging (magnetic resonance imaging [MRI], computed tomography [CT])
  
• Define specific radiographic characteristics of lesion
  
  
  
  • Diffuse (nonoperative)
    
  • Focal (operative)
    
  • Cystic components
    
  • Exophytic components (operative)
  
  
• Define position of lesion within the brain stem as rostral or caudal (i.e., cervicomedullary junction)
  
• Note degree of edema and enhancement pattern of lesion on MRI
  
• Note presence of calcium or hemorrhage within the lesion on noncontrast CT and MRI
  
• To differentiate between enhancement due to recurrent tumor and enhancement due to radiation necrosis, consider use of specialized imaging of metabolic activity (positron emission tomography scan, perfusion MR imaging)
  
• Use of stereotactic localization
  
• For patients with a diffuse nonenhancing lesion, consideration should be given to diagnostic alternatives (i.e., MR spectroscopy) or expectant management with serial imaging
  
• Lesion confined to the tectum does not require resection or biopsy, only close observation, and placement of a shunt (or third ventriculostomy) following development of obstructive hydrocephalus

Special Equipment

• Somatosensory evoked potentials
  
• Cranial nerve neurophysiologic testing: brain stem auditory evoked responses

Pterional Approach

• For tumors located predominantly in the ventral midbrain

Retrosigmoid Approach

• For lateral pontine-peduncle tumors

Far Lateral Approach

• For focal midline pontine lesions, medulla oblongata lesions, and lateral pontine-peduncle lesions

Supracerebellar/Infratentorial Approach

• For tumors located in the tectal plate with extension into the pineal region

Subtemporal Approach

• The subtemporal-transtentorial route is also a consideration for focal tumors in the ventrolateral pons

Transtentorial Approach

• The occipital-transtentorial approach with division of the tentorium laterally and along the straight sinus is another option for tectal tumors with extension into the pineal region

Stereotactic Biopsy

• Controversial because biopsy does not always ensure a diagnosis, but carries significant risk in this region; if considered, the trajectory should be down the middle cerebellar peduncle if possible because this minimizes the risk of bleeding from transecting several pial surfaces

Tumor Resection

• If tumor has an exophytic component, then begin resecting with this portion of the tumor
  
• Pursuing infiltrative lesions with aggressive resection is ill advised
  
• Diagnosis is confirmed with intraoperative review of frozen section by the neuropathologist
  
• Hemostasis of the resection cavity is methodically achieved with bipolar cautery (exercise great care to avoid injury to normal brain stem tissue), Avitene, Surgicel, or Gelfoam

• Slow steroid taper for high grade lesions and recurrent lesions
  
• Shorter steroid taper for low grade lesions
  
• Antibiotics continued for 24 hours
  
• Speech and swallowing assessment prior to advancing diet
  
• Close monitoring for development of hydrocephalus
  
• A postoperative MRI with and without contrast should be obtained within 48 hours for documentation of tumor resection and for future evaluation of response to adjuvant therapy