The Operation for Supratentorial Primitive Neuroectodermal Tumors in Children

Patient Positioning

• Tumor specific: Positioning depends on the specific location of the tumor.
• Head fixation: Pin fixation is used if the child is older than 3 year.  A horse-show headrest can be used if the child is younger than 3 years. 

Surgical Approach

Standard supratentorial craniotomies are used to approach both cerebral and suprasellar supratentorial PNETs.

• Intraoperative image guidance: The use of intraoperative computerized neuronavigational techniques can help with planning the craniotomy as well as provide some guidance during the resection of deeper aspects of the tumor. Intraoperative ultrasound may be used to assist in identification of unintended residual disease at the site of tumor resection.

Intervention

• Resection piecemeal: Supratentorial PNETs are typically vascular and are best removed in a piecemeal fashion with either suction or ultrasonic aspiration. Some supratentorial PNETs allow the surgeon to take advantage of a defined interface between brain and tumor. In other supratentorial PNETs, the boundary between brain and tumor is indistinct, and the surgeon is forced to create a dissection plane around the tumor or gradually debulk the tumor from within until a tumor-brain interface is reached.
• Radical resection favored: A radical resection is favored, although the effect of the amount of resection on prognosis is unclear. The extent of resection appears to correlate somewhat with local recurrence and survival (3, 4, 8, 10), including in the most recent SIOP study (11), although minimal residual tumor appears not to place patients in a more dangerous outcome category. However, the influence of extent of resection is perhaps less than the influence of postoperative therapy (both high-dose chemotherapy and radiation), and a proportional hazards model, including multiple patient factors and treatment factors, failed to show that extent of resection was independently associated with survival (1). Thus, prudence may dictate that the goal of surgery should be the maximal resection that can be achieved safely.

Closure

• Prevention of brain collapse: After a large tumor is removed, the superficial brain tends to collapse into the resection cavity, which may predispose to a postoperative subdural collection. If a linear cortisectomy was made to access the tumor, it may be possible to bring the edges of the cortex together and seal the cortical incision with a tissue or fibrin glue. Sometimes this is assisted by one or more fine pial sutures of 7-0 vicryl or similar. The resection cavity can then be inflated with fluid by inserting a catheter into the cavity via a puncture through the cerebral cortex away from the cortical incision. When the cavity has been filled, the catheter is removed and the hole from the catheter sealed with more tissue glue.
• Dural closure is usually possible primarily. If not, a graft may be placed. The authors typically use a piece of autologous pericranium, which is readily available in these operations. Watertight closure is preferable but is not critical.
• Bone flap replaced: The bone flap may be replaced according to the preference of the surgeon. The authors’ practice is to fixate the bone flap with absorbable Vicryl sutures, 3-0 for infants and 2-0 for older patients. Small pieces of bone, either full thickness in small children or part of the inner table in older children, are used as struts to place in the gap caused by loss of bone from the saw cuts. These struts of bone allow a more solid fixation of the bone flap with less probability of sinking in of the flap.
• Drains: The authors prefer to use no drains, but others prefer the routine use of subgaleal drains, which is also acceptable.
• Scalp closure: As per the preference of the individual surgeon. The authors use 3-0 or 4-0 interrupted vicryl for the galea and 3-0 or 4-0 continuous Vicryl rapide for the skin. This avoids the need for removal of skin sutures later.
• Dressing: Since only a small amount of hair is clipped along the incision line, the authors typically use a surgical skin sealant spray along the incision line. A loose dressing may or may not be placed over the incision after the spray. The dressing is to prevent the younger children from picking at the incision and also to prevent the bed sheets from getting dirty with blood products.