Indications for Procedure
Tectal gliomas of midbrain
- Indolent tumors causing few focal symptoms over time: Although the natural history is not well known, most tectal and periaqueductal tumors in children have indolent growth with few clinical symptoms. Often, management of hydrocephalus is followed by observation and serial MRI scans (41).
- Management of associated hydrocephalus: CSF diversion is typically the only required treatment for tectal gliomas causing obstructive hydrocephalus. Such patients are ideal candidates for ETV. Shunting is an alternative or can be considered for patients for whom ETV fails.
- Rarely require surgical resection: On rare occasions (e.g., growth or atypical radiological or clinical features), surgical resection may be considered.
Other focal tumors of the brainstem
- Unusual features confusing management: Surgery should be considered when the clinical features and/or imaging characteristics are not typical of a glioma.
- Changes mandating treatment: Whenever radiological or clinical signs of tumor progression are observed, biopsy or a more radical resection may be indicated.
Dorsally exophytic tumors
- Require removal of intraventricular or extraaxial component only: Long-term, event-free survival is expected when these tumors are simply shaved down to the level of the floor of the fourth ventricle. They should not be “chased” into the brainstem.
Diffuse intrinsic pontine gliomas
- Surgery is not indicated: It is generally accepted that surgical resection of diffuse intrinsic pontine gliomas is not safe due to their location and infiltrative nature. Biopsy is not indicated for patients with the typical clinical presentation and whose lesion has the typical appearance of a diffuse intrinsic pontine glioma on MRI. Hydrocephalus, if present, should be treated with either an ETV or a shunt. Histological confirmation might be needed if the radiographs or the clinical history are not typical for a diffuse intrinsic pontine glioma, or if an investigational protocol requests it. In these cases a surgical biopsy can be done.
- Managed as either spinal cord tumors or focal medullary tumors: Cervicomedullary tumors are treated in a fashion similar to that of an intramedullary spinal cord tumor or focal tumors of the medulla depending on the location of the tumor’s epicenter.
- Steroids best given for several days: Ideally, steroids should be administered for several days before surgery. If this is not possible, then a bolus dose should be administered at the beginning of the operation. Steroids should be continued through the operation with a rapid taper in the postoperative period. Stress-dose steroids should be strongly considered in patients who have been on these medications for a prolonged period of time before surgery.
- Antibiotics per local protocol: IV antibiotics should be administered before making the incision. The choice of agent(s) should be based on providing broad-spectrum coverage for skin flora, taking into consideration the local antibiotic resistance patterns.
- Pre-induction discussion to insure compatibility with monitoring needs: Great reliance is placed on the accuracy of the intraoperative physiological monitoring, so steps must be taken to insure that its effectiveness is not compromised by the anesthesia used during the case.
- Paralytics: Paralytics during intubation are acceptable but should be avoided intraoperatively due to adverse effects on intraoperative electrophysiological monitoring.
- Steady-state anesthesia: A continuous infusion intravenous anesthetic agent (e.g., propofol, fentanyl) is preferable owing to its minimal effects on monitoring.
- Avoidance: The avoidance of hypothermia, inhaled halogenated anesthetic agents, and intermittent injection of intravenous anesthetics is recommended, as these agents or events adversely affect monitoring.
- Operative microscope: The microscope is used to provide visualization and illumination of the operative field, particularly when working at the margins of the tumor.
- Intraoperative neurophysiological monitoring: This is a powerful tool that keeps the surgeon apprised of the tolerance of the brainstem to the surgery.
- Ultrasonic aspirator: The ultrasonic aspirator aids with central debulking of the tumor, as it has focused action in terms of tissue disruption with minimal spread to surrounding structures.
- Contact laser (e.g., Nd:YAG): A laser may be useful for coagulation of small pieces of tumor that are not separable from surrounding tissues.
- Stereotactic navigation: Stereotactic navigation equipment may aid in operative planning and localization of the tumor. Integration with advanced imaging techniques such as tractography (DTI) can help with avoidance of white matter tracts during resections. The versatility of this technology is limited once the resection is underway due to “brain sag” that is unavoidable with loss of CSF and tumor debulking. Intraoperative MRI can be used, if available, to provide “real-time” imaging, which can update the stereotactic localization.
- Ventriculostomy placement: A ventricular drain placed perioperatively may be useful in patients with symptomatic hydrocephalus.
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