Faculty Bibliography

BACKGROUND: Although uncommon, adverse radiation effects (ARE) are a potentially serious side effect of brain stereotactic radiosurgery (SRS). Corticosteroids are used to treat suspected ARE but side effects may be significant after long-term usage. Oral pentoxifylline (Ptx) and vitamin E therapy (VitE) are reported to benefit ARE seen in other organ systems. We treated 11 patients with suspected ARE after SRS with Ptx and VitE. METHODS: To assess the response, edema was measured using fluid-attenuated inversion recovery magnetic resonance imaging (MRI). Edema volumes were calculated by first determining the three maximum measurements in the X, Y, and Z planes of the image with the largest signal change. Volume was plotted over time for each patient that had serial MRI scans available. Two patients had 2 separate radiosurgeries and 2 patients underwent 3. Three patients received adjuvant whole-brain radiation therapy. RESULTS: The time until clinical detection of ARE after SRS varied from 3 to 18 months (median, 8 months). The change in edema volume varied from 59.6 ml in 1 patient (worse edema) to -324.2 ml (improvement). The average change in edema from pre- to post-treatment was -72.3 ml. One patient had more edema despite treatment; this patient was found to have tumor recurrence, and not an ARE. Two patients discontinued Ptx because of persistent nausea and abdominal discomfort. CONCLUSIONS: Ptx and VitE may be of benefit in the management of adverse radiation effects and should be studied further.

Management options for patients with vestibular schwannomas (acoustic neuromas) include observation, resection, stereotactic radiosurgery, or fractionated radiotherapy. In this report, we review our experience with radiosurgery over a 20-year interval, and discuss indications and expectations with the different approaches. There has been an evolution in available technologies, and an evolution in both patient and physician approaches to the management of this tumor. Patient decisions must be based on quality information from the peer-reviewed literature. Future concepts for radiosurgery are discussed.

Advances in central nervous system imaging have resulted in early detection of a greater number of intracanalicular vestibular schwannomas. Early detection of intracanalicular vestibular schwannomas raises the issue of whether or not treatment is required and, if so, whether radiosurgery is the most appropriate option. Available evidence indicates that a majority of intracanalicular lesions are observed to grow and most will be associated with progressive hearing loss or, less frequently, sudden persistent hearing loss. If the objective of treatment is to preserve serviceable binaural hearing, early intervention is advisable. Early intervention is advantageous only if serviceable hearing can be maintained in the majority of patients along with low perioperative morbidity. Radiosurgery seems to achieve these goals ideally. Radiosurgery is a minimally invasive management option for patients with intracanalicular tumors. Radiosurgery provides high rate of long-term hearing preservation with minimal morbidity.