Radiation Oncology/CNS/Trigeminal neuralgia/Treatment

Trigeminal Neuralgia Treatment Treatment Overview Medical (carbamazepine, phenytoin, gabapentin, baclofen) first, until failure Surgical Destructive: radiofrequency rhizotomy, glycerol rhizotomy, balloon compression, peripheral neurectomy Non-destructive: microvascular decompression Radiosurgery Gamma Knife Linac-based Medical treatment Meta-analysis (1960-2005) 17174762 -- "Drug treatment of trigeminal neuralgia: a systematic review of the literature." (Chole R, J Oral Maxillofac Surg. 2007 Jan;65(1):40-5.) 21 publications with high level of evidence (6 randomized, 15 controlled clinical trials), 348 patients Conclusion: Anticonvulsants effective, but difficult to compare/combine data in a scientifically meaningful manner Surgery Pittsburgh 1972-1991 -- "The Long-term Outcome of Microvascular Decompression for Trigeminal Neuralgia." (Barker et al. NEJM. 1996, 334:17, 1077-1083) Retrospective study of 1185 patients who underwent microvascular decompression. Immediate pain relief in 82%, partial 16%, and none in 2%. 75% had complete relief at 1 year, 9 % partial. 64% had complete relief at 10 years, 4 had partial (first surgery). 11% had re-operation for recurrent or refractory symptoms-total 80% had complete relief at 1 year and 8% partial, 70% had complete relief at 10 years, 4 had partial. Decision Analysis Queen Mary; 2007 17451880 -- "Decision analysis of medical and surgical treatments for trigeminal neuralgia: how patient evaluations of benefits and risks affect the utility of treatment decisions." (Spatz AL, Pain. 2007 Oct;131(3):302-10. Epub 2007 Apr 23.) 156 patients evaluated with time-trade-off utility measurement questionnaire Outcome: MVD highest maximum expected utility (16.08), followed by balloon compression (15.97), glycerol rhizolysis (15.61), and RFA (14.93). Meds alone worst at 14.61. Difference between highest and lowest treatments 7%, and sensitive to utility values Conclusion: Patients should consider surgery over meds, but treatment utility differences minimal SRS vs. Surgery Columbia; 2007 17167238 -- "Microvascular decompression vs. gamma knife radiosurgery for typical trigeminal neuralgia: preliminary findings." (Brisman R, Stereotact Funct Neurosurg. 2007;85(2-3):94-8.) Prospective protocol. 85 patients (GKS 61, MVD 24). GKS 75 Gy max. Outcome: CR (no pain, no meds): 1 year GKS 58% vs. MVD 68%; 2 years 24% vs. 68% (p=0.09) Toxicity: no permanent complications Conclusion: MVD more likely than GKS to result in complete pain relief UCSF 2005 16419978 -- "Management of medically refractory trigeminal neuralgia in patients with multiple sclerosis." (Cheng JS, Neurosurg Focus. 2005 May 15;18(5):e13.) Retrospective. 11 patients with TN-MS. Mean f/u 40 months Conclusion: Complete pain relief in TN-MS significantly more difficult than other TN, including highly refractory TN. SRS effective procedure, resulting in fewer retreatments, longer pain-free intervals compared with MVD or RF ablation 2005 16419977 1997-2004 -- "Recurrent or refractory trigeminal neuralgia after microvascular decompression, radiofrequency ablation, or radiosurgery." (Sanchez-Mejia RO, Neurosurg Focus. 2005 May 15;18(5):e12.) Retrospective. 32/209 patients treated with SRS, MVD or RFA required retreatment. Outcome: 19/93 MVD retreated (20%). 5/12 RFA retreated (42%), 8/108 (7.7%) SRS retreated, 2 with SRS. Conclusion: lowest re-treatment rates with SRS. SRS also more likely to be final treatment for recurrence, regardless of initial treatment Cooper University; 2005 1994-2002 16111575 -- "Glycerol rhizotomy versus gamma knife radiosurgery for the treatment of trigeminal neuralgia: an analysis of patients treated at one institution." (Henson CF, Int J Radiat Oncol Biol Phys. 2005 Sep 1;63(1):82-90.) Retrospective. 36/79 patients (GR) and 63/109 (GK) evaluated. RT 70-90 Gy to 100% isodose. Initial success: (Barrow I-III) 86% GR vs. 92% GK. Median time to relief <24hr GR vs. 3 weeks GK. Failure or pain recurrence: 53% GR vs. 42% GK (NS). Median time to failure 5mo GR vs. 8 mo GK (NS). End of treatment 39% GR vs. 24% GK failed Side effects: facial numbness 54% GR vs. 30% GK, bothersome 33% GR vs. 11% GK. GK lower pain score (OR 4.3) Conclusion: GR for acute pain relief, GK otherwise Mayo 2005 15951649 1999-2001 -- "A prospective cost-effectiveness study of trigeminal neuralgia surgery." (Pollock BE, Clin J Pain. 2005 Jul-Aug;21(4):317-22.) Prospective, nonrandomized. 126 patients (MVD 33, GR 51, SRS 69) Outcomes (6 months, 24 months): MVD (85%, 78%) vs. GR (61%, 55%) vs. SRS (60%, 52%). MVD > GR = SRS Cost per quality adjusted pain-free year: MVD $8174 vs. GR $6342 vs. SRS $8269 2005 15913282 1999-2004 -- "Comparison of posterior fossa exploration and stereotactic radiosurgery in patients with previously nonsurgically treated idiopathic trigeminal neuralgia." (Pollock BE, Neurosurg Focus. 2005 May 15;18(5):E6.) Retrospective. 55 patients PFE (MVD 89%, partial nerve section 11%), 28 patients SRS as initial treatment. RT mean dose 89.1 Gy. Mean f/u 25.5 months Outcome: Pain free at 1 year: 75% vs. 59% (SS). Additional surgery in 18% after PFE vs. 29% after SRS (NS) Side effects: facial numbness/dysesthesias: PFE 15% vs. SRS 43% Conclusion: PFE more effective as primary therapy Gamma Knife There is only one prospective trial published, from Marseille. At 1 year, 83% were pain free, with 58% off medications as well There are a number of retrospective, single institution studies published Target: ipsilateral trigeminal nerve adjacent to the pons with single shot 4mm collimator Dose: Typically 70-90 Gy Prospective Marseille, 2006 (France) 16776335 -- "Prospective controlled trial of gamma knife surgery for essential trigeminal neuralgia." (Regis J, J Neurosurg. 2006 Jun;104(6):913-24.) Phase I. 100 patients, 42 prior surgical treatment. RT: median dose 85 Gy (70 - 90 Gy). Minimum F/U 12 months, median ? Pain relief: 83/100 patients pain free at 12 months, 58/100 patients pain free and off meds. 17 patients underwent additional procedures Probability of worse outcome (SS and trend): <60 year old, isocenter-nerve emergence distance >8mm, large cistern surface, lower minimal nerve dose, prior procedure Side effects: Mild facial paresthesia 6%, hypesthesia 4% Retrospective Please see the Literature Review GKS Technique Brussels (Belgium) 2007 17689881 -- "Clinical Evaluation of Targeting Accuracy of Gamma Knife Radiosurgery in Trigeminal Neuralgia." (Massager N, Int J Radiat Oncol Biol Phys. 2007 Aug 7; [Epub ahead of print]) Retrospective. 78 patients treated with 90 Gy. 68 (83%) had follow-up MRI with focal nerve enhancement. F/U MRI fused with treatment MRI and correlated Outcome: Median deviation between pre and post MRI 0.91 mm. RT dose within contrast enhancement on post MRI median 77 Gy, range 49-85 Gy Conclusion: Median deviation low 2007 17415205 -- "Influence of nerve radiation dose in the incidence of trigeminal dysfunction after trigeminal neuralgia radiosurgery" (Massager N, Neurosurgery. 2007 Apr;60(4):681-7; discussion 687-8.) Comparative. 358 patients (109 Brussels, 259 Marseilles). Three dosimetry groups: Group I <90 Gy no blocking, Group II 90 Gy no blocking, Group III 90 Gy blocking Toxicity: mild Group I 15% vs. Group II 21% vs. Group III 49%; bothersome 1.4% vs. 2.4% vs. 10% Pain control: excellent 66% vs. 77% vs. 84%; good 81% vs. 85% vs. 90% Conclusion: Incidence of TN dysfunction and pain relief vary according to energy deposited to retrogasserian nerve root. Effect may be related to energy to nerve root rather than maximal dose delivered 2006 16682146 -- "Effect of beam channel plugging on the outcome of gamma knife radiosurgery for trigeminal neuralgia." (Massager N, Int J Radiat Oncol Biol Phys. 2006 Jul 15;65(4):1200-5.) Retrospective. 109 patients, 49 had channel blocking to brainstem. RT 90 Gy Blocking increased length of trigeminal nerve exposure, and thus mean dose. Outcome: better pain outcome (84% vs. 62% nonblocked), but worse trigeminal dysfunction (47% vs. 32%) 2004 15070111 -- "Gamma knife surgery for idiopathic trigeminal neuralgia performed using a far-anterior cisternal target and a high dose of radiation." (Massager N, J Neurosurg. 2004 Apr;100(4):597-605.) Retrospective. 47 patients. Mean f/u 16 months Pain relief: 68% excellent, 89% fair (>50%). Prognostic factors: higher dose, shorter distance to brainstem, development of facial sensory disturbance Side effects: Mild facial numbness 38%, bothersome 4% Conclusion: target nerve 5-8 mm from brainstem Wake Forest; 2006 17121135 -- "Does dose rate affect efficacy? The outcomes of 256 gamma knife surgery procedures for trigeminal neuralgia and other types of facial pain as they relate to the half-life of cobalt." (Balamucki CJ, J Neurosurg. 2006 Nov;105(5):730-5.) Retrospective. 239/326 patients. 80% experienced >50% pain relief, 56% complete relief Neither dose rate nor treatment time were significantly associated with control rate or degree of pain relief Conclusion: Consistent treatment any time during first half-life of Co source Columbia 2005 15850900 -- "Where to locate the isocenter? The treatment strategy for repeat trigeminal neuralgia radiosurgery." (Zhang P, Int J Radiat Oncol Biol Phys. 2005 May 1;62(1):38-43.) Retrospective. 40 patients with repeat GK. RT max 75 Gy initially, 40 Gy retreatment. Median f/u 28 months Pain relief: complete 27%, nearly complete 18%, partial 20%, minimal/none 35% Isocenter distance: mean 2.86 mm (complete/nearly complete relief) vs. 1.93 (partial/none relief). Farther distance with trend to better pain relief Side effects: 7% moderate dysesthesia (4/10), 3% severe dysesthesia (7/10) after retreatment. Not related to isocenter distance 2002 12015844 -- "Trigeminal Nerve-Blood Vessel Relationship as Revealed by High-resolution Magnetic Resonance Imaging and Its Effect on Pain Relief after Gamma Knife Radiosurgery for Trigeminal Neuralgia." (Brisman R, Neurosurgery. 2002 Jun;50(6):1261-6, discussion 1266-7.) Blood vessel - CNV contact evaluated. Group I (none) 24%, Group II (close) 17%, Group III (contact) 59%. Contact more often in men (SS), more often with unilateral TN. If no prior surgery, BV-CNV contact may be prognostic factor 2000 11143235 -- "Gamma knife radiosurgery for trigeminal neuralgia: dose-volume histograms of the brainstem and trigeminal nerve." (Brisman R, J Neurosurg. 2000 Dec;93 Suppl 3:155-8.) Volume of brainstem that receives >20% of Dmax (VB20), and volume of trigeminal nerve that receives >50% of Dmax (VT50) assessed VB20 excellent pain control: 6 months <20mm3 32% vs. >20mm3 56% (SS), 12 months <20mm3 27% vs. >20mm3 50% (SS) VB20 is lower in TN-MS. VB20 is inversely related to VT50 Conclusion: isocenter proximity to brainstem (reflected by higher VB20) is better Upstate 2005 1998-2003 15662807 -- "Gamma knife surgery for trigeminal neuralgia: improved initial response with two isocenters and increasing dose." (Alpert TE, J Neurosurg. 2005 Jan;102 Suppl:185-8.) Retrospective. 63 patients, 1 shot in 27 vs 2 shots in 36 patients. Dose 20 patients <=80 Gy, 21 patients 85 Gy, 22 patients >=90 Gy. Pain evaluated using BNI scale Pain relief: Initial 90%, overall 27%. Facial numbness 8% Number of shots: "2" 2.83 BNI improvement vs. "1" 1.72 BNI improvement (SS) Dose: SS improvement with each higher dose group Maryland 2005 ASTRO Abstract 2336 -- "Evaluating the Influence of Dose-Rate on Outcome with Gamma-Knife Stereotactic Radiosurgery in the Treatment of Trigeminal Neuralgia" (Patel S) Retrospective. 61 patients. 31 prior to source change, 30 after source change. RT dose 75 Gy (70-80 Gy). Median f/u 30 months Dose rate: 161.6 cGy/min (151-179) vs. 342.9 cGy/min (321-366) Pain control: 61% vs. 83% (SS). Recommend dose escalation below dose rate 179.4 cGy/min Side effects: 16% vs. 10% (NS) 2004 15380590 1996-2001 -- "Gamma knife surgery for trigeminal neuralgia: outcome, imaging, and brainstem correlates." (Cheuk AV, Int J Radiat Oncol Biol Phys. 2004 Oct 1;60(2):537-41.) Retrospective. 96/112 patients. RT 75 Gy (60-80Gy) Imaging: 58% good, 31% fair, 10% poor. No correlation to outcome Dose to brain stem: 44% received 10% of Dmax, 56% received 20% of Dmax. No correlation to outcome Nerve compression: 11% by MRI. No correlation to outcome 2004 15379025 -- "Selective source blocking for Gamma Knife radiosurgery of trigeminal neuralgia based on analytical dose modelling." (Li K, Phys Med Biol. 2004 Aug 7;49(15):3455-63.) Algorithm to selectively block sources to minimize dose to brainstem. Moderate number of plugs (30-50) significantly lowers (40%) dose to brainstem. No mention of dose to trigeminal nerve in abstract 2003 12870587 -- "A technique to sharpen the beam penumbra for Gamma Knife radiosurgery." (Guerrero M, Phys Med Biol. 2003 Jun 21;48(12):1843-53.) Physical penumbra (defined as distance 90% to 50% isodose) typically 1-2 mm. Technique to insert a conic filter into individual plug collimator to flatten beam profile Able to reduce single penumbra width by 30-60%, at cost of reduced beam intensity by 20-50% 2005 Northwest Hospital (Seattle) ASTRO Abstract -- "Dose-Response and Dose-Complication Relationships in Stereotactic Radiosurgery for Trigeminal Neuralgia" (Meier R, Abstract 2353) Retrospective. 252 patients, typical or atypical TN. RT to 76 Gy (58 patients), 87 Gy (101 patients), or 98 Gy (93 patients) using 0.87 output factor. Mean f/u 3.9 years, 2.0 years, 1.7 years Pain control: favorable 74%, 75%, 76% (NS) Side effects: sensory deficit 9%, 22%, 39% (SS) Conclusion: dose escalation doesn't improve pain control, but has more complications Cleveland Clinic 2004 15007220 -- "Gamma knife radiosurgery for trigeminal neuralgia: comparing the use of a 4-mm versus concentric 4- and 8-mm collimators." (Kanner AA, Stereotact Funct Neurosurg. 2004;82(1):49-57.) 101 patient evaluated, 54 treated with 4-mm helmet, and 47 with 4/8-mm helmet. RT 75 Gy to 100% isodose line No difference in outcome Royal Hallamshire 2002 (UK) 12507100 -- "The clinical application of plugging patterns for the Leksell gamma knife." (Vaughan P, J Neurosurg. 2002 Dec;97(5 Suppl):579-81.) Plugging significantly improved conformity and reduced brain stem exposure, without altering length of TN treated Mayo 2001 11440460 1997-1999 -- "High-dose trigeminal neuralgia radiosurgery associated with increased risk of trigeminal nerve dysfunction." (Pollock BE, Neurosurgery. 2001 Jul;49(1):58-62; discussion 62-4.) Retrospective. 68 patients. 40% 70 Gy, 60% 90 Gy. Mean f/u 14.4 months Pain control: 70 Gy 41% pain free vs. 90 Gy 61% (NS) Side effects: 70 Gy 15% TN dysfunction vs. 90 Gy 54% (SS). Bothersome in 4% vs. 32%. Corneal numbness in 3/41 (8%). Pain control better in those with TN dysfunction Conclusion: recommend dose <90 Gy Comment in 12051192 "High-dose trigeminal neuralgia radiosurgery associated with increased risk of trigeminal nerve dysfunction." (Regis J, Neurosurgery. 2002 Jun;50(6):1401-2; author reply 1402-3.) Pittsburgh 2001 11567820 -- "Does increased nerve length within the treatment volume improve trigeminal neuralgia radiosurgery? A prospective double-blind, randomized study." (Flickinger JC, Int J Radiat Oncol Biol Phys. 2001 Oct 1;51(2):449-54.) Randomized. 87 patients. RT 75 Gy to 1 or 2 isocenters. Median f/u 26 months Pain relief: excellent 52%, good (low dose meds) 14%, partial 17%, failed 17%. Identical for 1 or 2 isocenters. Relapse in 42% of responding patients Side effects: 14% of 2 isocenters vs. 7% of 1 isocenter (NS). Complications correlated (SS) to nerve length irradiated Linac Linac Outcomes Wisconsin 2005 16331167 -- "Linear accelerator radiosurgery for trigeminal neuralgia." (Richards GM, Neurosurgery. 2005 Dec;57(6):1193-200; discussion 1193-200.) Retrospective. 28 patients. RT 80 Gy with 4-mm collimator and 7-arc technique. Median f/u 12 months Outcome: 57% complete pain relief, 75% 3 point pain reduction (10 point scale). Median time to pain relief 1 month. Mean time to pain recurrence 14 months. Women longer mean time to pain recurrence (16 vs. 7 months) Side effects: 3 patients mild facial numbness; 1 neurotrophic keratopathy Stanford 2005 15913285 2002-2004 -- "CyberKnife radiosurgery for idiopathic trigeminal neuralgia." (Lim M, Neurosurg Focus. 2005 May 15;18(5):E9.) Retrospective. 41 patients with typical TN. Mean follow-up 11 months Pain control: Initial 93% at median 7 days. Pain control 88% excellent, 5% moderate, 7% no change. Recurrence 16%, median time to recurrence 6 months. Long term response (@ 11 months) 78% Higher prescribed doses not associated with pain relief or recurrence rate. Hypesthsia rate related to length of trigeminal nerve treated 2003 14742972 -- "Cyberknife radiosurgery for trigeminal neuralgia." (Romanelli P, Stereotact Funct Neurosurg. 2003;81(1-4):105-9.) Preliminary report. CT cisternography for localization. 10 patients, 7 achieved pain relief. Minnesota 2004 15637446 -- "Long-term follow-up of trigeminal neuralgia treatment using a linear accelerator." (Kubicek GJ, Stereotact Funct Neurosurg. 2004;82(5-6):244-9.) Retrospective. 20 patients. RT 82.3 - 100 Gy. Median f/u 56.5 months Pain control: 35% complete, 78% >50% improvement. Recurrence 63%, mean interval 21.5 months Kaiser Permanente 2004 2002-2003 15537188 -- "Treatment of trigeminal neuralgia with linear accelerator radiosurgery: initial results." (Chen JC, J Neurosurg. 2004 Nov;101 Suppl 3:346-50.) Retrospective. Novalis. 32 patients treated. RT 85-90 Gy in 5- or 7- noncoplanar arcs with 4-mm collimator. For GKS retreatment, 60 Gy dose Pain relief: BNI I-III in 78% patients, median time to relief 6 weeks. UCLA 2004 14981193 -- "Noninvasive linear accelerator radiosurgery as the primary treatment for trigeminal neuralgia." (Frighetto L, Neurology. 2004 Feb 24;62(4):660-2.) Retrospective. 22 patients treated on dedicated Linac Pain control: 95.5% significant pain relief 2003 14519214 1999-2001 -- "Linear accelerator radiosurgery using 90 gray for essential trigeminal neuralgia: results and dose volume histogram analysis." (Goss BW, Neurosurgery. 2003 Oct;53(4):823-8; discussion 828-30.) Retrospective. 25 patients. RT 90 Gy with 5-mm collimator. Median f/u 18 months Pain relief: 76% excellent, 100% >50% relief Side effects: 32% facial numbness, none painful. No correlation with brainstem volume 2003 12959439 1995-2001 -- "Dedicated linear accelerator radiosurgery for the treatment of trigeminal neuralgia." (Smith ZA, J Neurosurg. 2003 Sep;99(3):511-6.) Retrospective. 60 patients, 68% essential TN, 20% secondary, 11% atypical. RT mean 83 Gy (70-90 Gy). 5-mm collimator in 75% patients, 7.5-mm collimator in 25% patients. Mean f/u 23 months Pain relief: essential TN 56% excellent, 88% good+excellent; secondary pain 58% significant; atypical pain "worse results". Relief experienced at mean 2.7 months Side effects: 25% new numbness 2002 ASTRO Abstract 1995-2001 -- "Linear Accelerator Radiosurgery Comparing 90Gy and Less Than 90 Gy for Essential Trigeminal Neuralgia" (Goss B, Abstract 247, 2002) Retrospective. 41 patients treated. RT dose 70-85 Gy (16 patients), 90 Gy (25 patients). Median f/u 13 months Pain control: 70-85Gy - 37% excellent, 31% good. Relapse 50%. 90Gy - 76% excellent, 24% good. Relapse 32%. Length of pain relief, good&excellent response better in 90Gy Side effects: 70-85Gy - 31% numbness, none bothersome. 90Gy - 32% numbness, none bothersome Linac technique Maryland 16264249 -- "Comparative analyses of linac and Gamma Knife radiosurgery for trigeminal neuralgia treatments." (Ma L, Phys Med Biol. 2005 Nov 21;50(22):5217-27.) Dose fall-off and set-up error tolerance of linac vs. Gamma Knife Equivalent dose fall-off with high number of arcs. However, increased treatment time and icocenter accuracies a concern Minnesota 15753942 -- "Linac-based stereotactic radiosurgery for treatment of trigeminal neuralgia." (Gerbi BJ, J Appl Clin Med Phys. 2004 Summer;5(3):80-92.) Accuracy comparable to Gamma Knife, dose distributions equivalent. Disadvantage time involved. Outcome Evaluation ESI-55 1556879 -- "A health-related quality of life instrument for patients evaluated for epilepsy surgery." (Vickerey BG, Med Care. 1992 Apr;30(4):299-319.) 55 item scale to measure health-related quality of life in epilepsy patients Reliable, valid, sensitive to differences in seizure status Used by Marseille group in the prospective TN trial to evaluate QOL Serious SRS side effects Semmelweist; 2007 (Hungary) 17317993 -- "Pathological findings following trigeminal neuralgia radiosurgery." (Szeifert GT, Prog Neurol Surg. 2007;20:244-8.) Case report. Retreatment, initial dose 90 Gy distally, followed by 70 Gy proximally. Hemorrhagic stroke 26 days after 2nd treatment Autopsy: neurovascular conflict close to 2nd shot, with acute and chronic radiation-induced lesions in trigeminal nerve Amakusa; 2005 (Japan) 16167795 -- "[A case of delayed facial palsy following gamma knife radiosurgery for intractable trigeminal neuralgia]" [Article in Japanese] (Itai K, Masui. 2005 Sep;54(9):1018-20.) Case report. 77 y/o F. SRS RT 77 Gy. After 20 months developed left facial palsy with hydropsia, left xerophthalmia, left facial hypesthesia. Resolved over several months on oral prednisolone Mayo 2004 15317722 -- "Vision loss as a complication of gamma knife radiosurgery for trigeminal neuralgia." (Naseri A, Br J Ophthalmol. 2004 Sep;88(9):1225-6.) Case report. RT 40 Gy to the 50% isodose line. Presented 15 months later Initial exam showed vision 20/25, fine punctate epitheliopathy, no corneal sensation. 10 weeks later vision 20/200, severe epithelial keratopathy. Punctal plug placed, artificial tears, vision returned to 20/60 over 6 weeks 2000 11077103 -- "Radiation induced vascular injury after stereotactic radiosurgery for trigeminal neuralgia: case report." (Maher CO, Surg Neurol. 2000 Aug;54(2):189-93.) Case report. SRS failed, patient underwent MVD. At operation, two adjacent veins and the superior cerebellar artery noted to have focal changes consistent with atheromatous disease. Chiba; 2002 (Japan) 12507089 -- "Gamma knife radiosurgery for trigeminal neuralgia: the dry-eye complication." (Matsuda S, J Neurosurg. 2002 Dec;97(5 Suppl):525-8.) Retrospective. 33/41 patients treated with GKS to 80 Gy, 4-mm collimator, single isocenter. Mean f/u 13 months 3 patients reported "dry eye", with diminution/absence of corneal reflex. No other abnormalities. Hypesthesia of V1 developed prior to "dry eye". Brain stem irradiated volume significantly correlated with complication UCLA; 1997 9018707 -- "Leksell Gamma Knife treatment of tic douloureux." (Rand RW, Neurosurg Clin N Am. 1997 Jan;8(1):75-8.) Retrospective. 12 patients. F/u 3-4 years. Pain control: 8/12 improvement or complete relief. Side effects: 1 radionecrosis in medial temporal lobe Radiobiology Maryland 11674826 -- "An investigation of eye lens dose for gamma knife treatments of trigeminal neuralgia." (Ma L, J Appl Clin Med Phys. 2000 Autumn;1(4):116-9.) Phantom studies and in vivo dosimetry for 6 patients. Average dose to ipsilateral lens 7.7 cGy (+/- 0.6 cGy). Calculated cataract probability 0.1% Pittsburgh 10764273 -- "Histological effects of trigeminal nerve radiosurgery in a primate model: implications for trigeminal neuralgia radiosurgery." (Kondziolka D, Neurosurgery. 2000 Apr;46(4):971-6; discussion 976-7.) 2 adult baboons SRS to 80 and 100 Gy (4 nerves total). Target proximal trigeminal nerve just anterior to pons. Nonirradiated baboon brains as controls. 6 months after MRI and pathology MRI: 4 mm area of contrast enhancement Pathology: axonal degeneration, mild edema, with remnants of myelinated axons. Large and small myelinated and unmyelinated fibers affected. No inflammation. Nerve necrosis at 100 Gy treatment. Trigeminal ganglion normal. NCI 7607923 -- "Clinical toxicity of peripheral nerve to intraoperative radiotherapy in a canine model." (Johnstone PA, Int J Radiat Oncol Biol Phys. 1995 Jul 15;32(4):1031-4.) 40 animals, laparotomy with IORT 0-75 Gy to lumbosacral plexus. Then periodically sacrificed to monitor peripheral nerve. F/u 5 years Dose >= 25 Gy resulted in ipsilateral neuropathy. Inverse relationship between dose and time-to-neuropathy, ED50 for paralysis 17.2 Gy. One animal treated with 15 Gy IORT developed paralysis after much longer latency. Consider 15 Gy threshold for paralysis. Historical Note 9309292 -- First use of RT for trigeminal neuralgia in 1897 15397004 -- "Roentgenotherapy in trigeminal neuralgia." (Trostler IS, Miss Valley Med J. 1949 Nov;71(6):204.)