Radiation Oncology/CNS/Trigeminal neuralgia/Overview

Trigeminal Neuralgia Epidemiology 15,000 new cases in US per year; incidence 4/100,000 - 5/100,000 Majority of idiopathic TN after age 50 Definition International Headache Society Classical TN (also called Idiopathic, or tic douloureux) A) Paroxysmal attack lasting from fraction of a second to 2 minutes, affecting one or more of the trigeminal nerve divisions B) One of the two following: 1) intense, sharp, superficial, stabbing or 2) precipitated from trigger areas or by a trigger factor C) Stereotyped in the individual patient D) No other neurological deficits E) Not attributed to another disorder Symptomatic TN (also called Secondary) Symptoms indistinguishable from Classical TN but caused by a demonstrable structural lesion (e.g. neuroma, vascular compression) Signs and symptoms Idiopathic has five classical features: Paroxysmal Provokable Unilateral Confined to the trigeminal nerve distribution Unassociated with gross trigeminal motor or sensory loss. Atypical TN is any pain that lacks the 5 classical features. Multiple sclerosis-associated TN similar pain as idiopathic, but in the setting of MS Typically does not wake patient up at night Unilateral in most cases, if bilateral then not simultaneously Trigger zones in distribution of CN V, include light touch, chewing, talking, brushing teeth, cold air, smiling/grimacing Pain Scales Barrow Neurological Institute (BNI) Grade I no pain, no medication Grade II occasional pain, no medication Grade IIIa no pain, medication Grade IIIb pain, medication controlled Grade IV pain, not well controlled Grade V no pain relief Marseille scale Class I no pain, no medication Class II no pain, medication Grade III >90% pain frequency reduction Grade IV >50% pain frequency reduction Grade V no significant pain relief Grade VI pain worsening Etiology Idiopathic TN Compression of trigeminal nerve by aberrant artery or vein suspected in 80-90% of cases Resulting demyelination somehow triggers TN (possibly via ephaptic cross-talk between fibers mediating light touch and pain) Also evidence for central pain mechanisms (refractory period after episode, trans of pain after single stimulus, latency from stimulus to onset) Secondary TN Caused by other structural compressions (e.g. vestibular schwannoma, meningioma, epidermoid cyst, aneurysm, AVM) Oregon, 2004 15540931 -- "Pathophysiology of trigeminal neuralgia: new evidence from a trigeminal ganglion intraoperative microneurographic recording. Case report. (Burchiel KJ, J Neurosurg. 2004 Nov;101(5):872-3.) Intraop recordings suggest TN pain generated by an abnormal discharge within peripheral NS, both in trigeminal ganglion neurons and/or the nerve itself Anatomy Trigeminal nerve (CN V) supplies sensory to the face, and sensory and motor to muscles of mastication V1 - Ophthalmic V2 - Maxillary V3 - Mandibular Nerve exits at midlateral surface of the pons Meckel's cave - gasserian ganglion (sensory ganglion), located 2 cm anterior to trigeminal root entry zone. Imaging Thin slice (1mm) MRI/MRA to rule out structural lesions. Sensitivity and specificity for identifying vascular compression 89% and 50% Tufts 2006 16436823 -- "Nerve atrophy in severe trigeminal neuralgia: noninvasive confirmation at MR imaging--initial experience." (Erbay SH, Radiology. 2006 Feb;238(2):689-92.) 31 patient MRIs reviewed. Mean diameter on symptomatic side 2.11 mm vs. 2.62 mm (SS). Mean cross-sectional area 4.50 mm2 vs. 6.28 mm2 (SS) 2005 15662790 -- "Targeting the cranial nerve: microradiosurgery for trigeminal neuralgia with CISS and 3D-flash MR imaging sequences." (Zerris VA, J Neurosurg. 2005 Jan;102 Suppl:107-10.) Multiple imaging sequences evaluated. CISS/3D-Flash preferred method MC Wisconsin 16029818 -- "Effect of image uncertainty on the dosimetry of trigeminal neuralgia irradiation." (Jursinic PA, Int J Radiat Oncol Biol Phys. 2005 Aug 1;62(5):1559-67.) Conclusion: uncertainty of target by MRI >2x than by CT. 4&8 mm collimator higher isodose line than 4mm collimator UCLA 15730595 -- "Three-dimensional fast imaging employing steady-state acquisition magnetic resonance imaging for stereotactic radiosurgery of trigeminal neuralgia." (Chavez GD, Neurosurgery. 2005 Mar;56(3):E628; discussion E628.) Evaluation of 3-D-FIESTA sequence in 15 patients. 3-D-FIESTA sequence successfully demonstrated the trigeminal complex (root entry zone, trigeminal ganglion, rootlets, and vasculature) in 14 patients (93.33%). The 3-D-FIESTA sequence also allowed visualization of the branches of the trigeminal nerve inside Meckel's cavity. Conclusion: SRS targeting of specific trigeminal branches may be feasible Rosewell Park 11733329 -- "Focal enhancement of cranial nerve V after radiosurgery with the Leksell gamma knife: experience in 15 patients with medically refractory trigeminal neuralgia." (Alberico RA, AJNR Am J Neuroradiol. 2001 Nov-Dec;22(10):1944-8.) Retrospective. 15 patient MRIs. RT dose 35-45 Gy at 50% isodose line. Mean time to follow-up imaging 61 days Target enhancement in 10/15; remaining 5 had RT dose 35 Gy Treatment Please see the treatment and retreatment pages Cost-Effectiveness Mayo 1999-2001 15951649 -- "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 14677455 -- "CSNS Resident Award: the economics of trigeminal neuralgia surgery." (Ecker RD, Clin Neurosurg. 2003;50:387-95.) No abstract