title: Focal enhancement of cranial nerve V after radiosurgery with the Leksell gamma knife: experience in 15 patients with medically refractory trigeminal neuralgia.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Departments of Diagnostic Radiology (R.A.A.) and Neurosurgery (R.A.F., J.L.), Roswell Park Cancer Institute, Buffalo, NY.
authors.forename: R A
authors.initials: RA
authors.lastname: Alberico
authors.forename: R A
authors.initials: RA
authors.lastname: Fenstermaker
authors.forename: J
authors.initials: J
authors.lastname: Lobel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003391:Cranial Nerves / Q000473:pathology*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000295:instrumentation; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D014276:Trigeminal Nerve / Q000473:pathology*; D014277:Trigeminal Neuralgia / Q000473:pathology / Q000601:surgery*
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA