Positioning: Regardless of the position used, proper positioning of the patient, particularly with respect to neck flexion or rotation and shoulder placement, is important for adequate visualization of the tumor being addressed.
Head holder: Rigid fixation with the Sugita or Mayfield head holder with skull pins should be considered, particularly when intraoperative navigation will be used. For smaller patients or those with thinner skulls, gel pad adapters available for some versions of the Mayfield head holder should be considered.
Prone position good for most: With the exception of upper midbrain tumors, the prone position provides appropriate surgical access to the length of the brainstem. The patient is positioned prone on chest rolls to minimize compression of the abdominal compartment. The neck should be adequately flexed and the shoulders positioned to provide optimal access to the posterior fossa and the upper cervical spine.
Sitting position occasionally useful: The sitting position can also be used for many tumors of the brainstem. However, the increased risk of pneumocephalus, air embolism, and surgeon fatigue must be weighed in considering this position.
¾ Lateral, park bench: This position can be used for lateral tumors within the brainstem or for larger patients. It is most commonly used when approaching the pons and midbrain.
Lateral: This position is preferred when using a subtemporal approach to the midbrain.
Keen’s or Dandy’s point in surgical field: Although uncommon, Keen’s or Dandy’s point should be identified and consideration given to leaving it in the operative field should the need for placement of an EVD arise.
Approach: The approach to the brainstem is predominantly through the posterior fossa, but the subtemporal approach may be useful for some midbrain tumors.
Mapping for tracts and nuclei: Except for exophytic tumors, most brainstem gliomas are hidden within the brainstem, and an incision into the stem is required. Mapping of the area can locate important nerve tracts and nuclei to be avoided during the resection.
Resection by central debulking: The basic technique for removal of intrinsic brainstem tumors is to start in the center of the tumor and move to its margins. Resection stops as the margins begin to appear. The exception is the dorsally exophytic tumor, which is shaved flush with the floor of the ventricle, removing only that portion of the tumor that lies within the ventricle.
Primary closure of dura: Primary closure of the dura in a water-tight fashion is preferred. Grafting with a dural substitute can be performed as needed.
Replace bone when possible: If possible, the bone from the craniotomy and laminotomies should be replaced using plating or sutures.
Fascial closure important: Fascial closure should be water-tight as this is the layer that prevents CSF leakage.
Drains: Surgical drains are typically not placed postoperatively unless there is concern for inadequate hemostasis during closure.
Managing Associated Hydrocephalus
CSF circulation: CSF diversion may be necessary when brainstem tumors cause obstructive hydrocephalus. Traditional ventriculoperitoneal shunting can be considered. However, many patients are excellent candidates for ETV.