American Journal of Neuroradiology 22:1944-1948 (November 2001)
© 2001 American Society of Neuroradiology
BRAIN
Focal Enhancement of Cranial Nerve V after Radiosurgery with the Leksell Gamma Knife: Experience in 15 Patients with Medically Refractory Trigeminal Neuralgia
a From the Departments of Diagnostic Radiology (R.A.A.) and Neurosurgery (R.A.F., J.L.), Roswell Park Cancer Institute, Buffalo, NY.
BACKGROUND AND PURPOSE: Gamma knife radiosurgery is an alternative for the treatment of medically refractory trigeminal neuralgia. Few reports of posttreatment MR imaging appearance of cranial nerve V exist. Our purpose was to define MR imaging characteristics in cranial nerve V after gamma knife radiosurgery.
METHODS: We retrospectively reviewed MR images of 15 patients who underwent gamma knife radiosurgery for trigeminal neuralgia. Radiation doses were 35–45 Gy at the 50% isodose line. Thin-section T2-weighted images and contrast-enhanced and nonenhanced T1-weighted images were obtained the day of radiosurgery and within the next 5 mo. Images were scored for enhancement and hyperintensity on T2-weighted images. Time to follow-up imaging and radiation dose were recorded.
RESULTS: Mean time to follow-up imaging was 61 ± 29 d. Posttreatment T2-weighted images showed stable signal intensity in all cases, with radiosurgical target site enhancement in 10. All five patients whose images did not show treatment-related enhancement received radiation doses of 35 Gy. The data suggested a correlation between enhancement with radiation dose (P = .06). No correlation of enhancement with treatment response or time to follow-up existed (P > .05).
CONCLUSION: The trigeminal nerve often enhances at the target site after radiosurgery. Lack of trigeminal nerve enhancement occurred only with lower doses (35 Gy at 50%). MR imaging may be useful to confirm the presence and location of the treatment site after gamma knife radiosurgery for trigeminal neuralgia.