Interventional Procedures for Trigeminal Neuralgia

1. Interventional Procedures for Trigeminal Neuralgia Dr. Edmond Chung Pain Team QEH

2. Contents • Methods • Theory • Indications • Limitations • Contraindications • Anatomy • Set up • Equipments

3. Contents (cont’d) • Technique • Side Effects & Complications • Efficacy • What if the pain recurs ? • Peripheral nerve blocks

4. Methods • Chemical – Glycerol • Radiofrequency thermocoagulation of Trigeminal Ganglion • Maxillary & Mandibular nerve blocks • Peripheral nerve blocks of the branches of Trigeminal nerve – supraorbital, infraorbital, mental nerve blocks

7. Indications • Trigeminal Neuralgia refractory to non-invasive means of Rx – V1, V2 or V3 dermatomes

9. Contraindications • Space-occupying lesions or microvascular compression in brain, esp brainstem (Check CT or MRI first!) • Coagulopathy • Infection • Uncooperative patient • Patient refusal

10. Anatomy • Middle cranial fossa • Dorsal & cranial to foramen ovale • Medial to the gasserian ganglion is the carotid artery & cavernous sinus • V1 (ophthalmic part) – most medial & greatest distance to the foramen ovale • V2 (maxillary part) – central • V3 (mandibular part) – most lateral & superficial

18. Limitations • Pts who want to avoid numbness of face as result of RF • Pain in V1 dermatome

19. Equipments • RF generator • RF cannulae • RF probes • RF ground electrode • X-ray Image Intensifier (C-arm)

22. Set Up

25. Technique - landmark

39. Technique • Pt on horizontal recumbent position • Head fixed on a radiolucent head rest by adhesive bandage • Under MAC (using TCI / TIVA technique) • Fluoroscopic guidance • Essential to obtain an optimal picture of foramen ovale • C-arm 45 deg caudal / cranial & 15-20 deg sideways

40. Technique (cont’d) • 22G 10cm RF needle with a 2mm free tip inserted along the direction of radiation beam (tunnel-vision technique) • N.B. beware piercing of oral mucosa • Needle advanced towards foramen ovale • Once needle enters the foramen, a clear “give” perceived • Check with lateral view on the depth of penetration – intersection of clivus & ospetrosum

41. Technique (cont’d) • Sensory Stimulation • Freq : 100 Hz • Voltage : 0.1-0.5V • The aim : to elicit paresthesia or pain in the division of trigeminal nerve, which you wish to lesion • Motor Stimulation • Freq : 2 Hz • Voltage : less than 1V • If you see contractions of masseter muscle, advance the needle deeper into the foramen ovale.

42. Technique (cont’d) • Lesion mode (additional bolus of IV propofolfirst) : • Lesion at 60 deg C for 60 sec • Allow to wake up after 1st lesion  retest with pin prick or sensory stimulation • Adjust position of needle or advance further accordingly • Re-institute GA • Repeat lesioning in 5 deg C increments for 60 sec each • At each stage, allow pt to wake up & retest with pin prick or sensory stimulation • Check corneal reflex

43. Results • Long term (years) success rates vary from 80 – 90%

44. Complications • Corneal anesthesia / hyperesthesia – 13.7% • Dysesthesia in the treated area 5-7% • Masseter weakness 1-2%

45. Morbidity & Mortality • Low morbidity • Can be performed on an out-patient basis • Mortality has not been reported

46. What if the pain recurs ? • For repeated RF • To review with CT or MRI brain at intervals to exclude SOL • Refer to Neurosurgery for consideration of Gamma Knife or Radiosurgery

47. Maxillary or Mandibular Nerve Blocks