Cerebellopontine Angle Syndrome - Treatment: Stereotactic Radiotherapy

Treatment: Stereotactic Radiotherapy

Stereotactic radiotherapy has emerged within the last 20 years as an alternative to microsurgery for selected patients with acoustic neuroma.

• Stereotactic radiation therapy makes use of one of several radiation sources and is administered using a variety of different machines with proprietary names (e.g., Gamma Knife, CyberKnife, BrainLAB).
• Stereotactic therapy uses radiation delivered to a precise point or series of points to maximize the amount of radiation delivered to target tissues while minimizing the exposure of adjacent normal tissues. It can be delivered as a single dose or as multiple fractionated doses.
• The effects of radiation delivered at the current low dose likely prevents further tumor growth by causing obliterative endarteritis of the vessels supplying the tumor. Radiosurgery may affect tumor cells undergoing mitosis by causing double strand DNA breaks. Hansen et al. demonstrated acoustic neuroma cells are radioresistant at the current low-dose radiation used with radiosurgery.3
• Comparison of microsurgery and stereotactic radiation is difficult for the following reasons:
  • Tumor size is inconsistently reported in the literature.
  • Data using the lower radiation dosages are available for only the past 10 years.
  • Because the goal of radiotherapy is control of tumor growth, understanding whether posttreatment neuroimaging reflects adequate treatment or merely the natural history of vestibular schwannomas is difficult.
  • No data concerning the risk for secondary tumor induction by radiotherapy are available.

Advantages of radiation therapy include decreased length of stay, decreased cost, rapid return to full employment, and lower immediate posttreatment morbidity and mortality.

Disadvantages of stereotactic radiation are:

• Necessity for regular monitoring and frequent rescanning (In the end, costs associated with long-term monitoring could exceed those of surgery.)
• Does not eliminate the tumor and may fail to control tumor growth, sometimes requiring salvage surgery.
• Higher incidence of trigeminal nerve injury.
• Unknown long-term incidence of secondary malignancies. The best current estimates of developing a secondary malignancy from the radiosurgery are 1 in a 1000 patients over 30 years.
• Does not address disequilibrium and may lead to long-term balance dysfunction.