Interventional Procedures for Trigeminal Neuralgia Dr. Edmond Chung Pain Team QEH Contents • • • • • • • • Methods Theory Indications Limitations Contraindications Anatomy Set up Equipments Contents (cont’d) • • • • • Technique Side Effects & Complications Efficacy What if the pain recurs ? Peripheral nerve blocks 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 Indications • Trigeminal Neuralgia refractory to noninvasive means of Rx – V1, V2 or V3 dermatomes Contraindications • Space-occupying lesions or microvascular compression in brain, esp brainstem (Check CT or MRI first!) • Coagulopathy • Infection • Uncooperative patient • Patient refusal 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 Limitations • Pts who want to avoid numbness of face as result of RF • Pain in V1 dermatome Equipments • • • • • RF generator RF cannulae RF probes RF ground electrode X-ray Image Intensifier (C-arm) Set Up Technique - landmark 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 Technique (cont’d) • 22G 10cm RF needle with a 2mm free tip inserted along the direction of radiation beam (tunnelvision 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 & os petrosum 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. Technique (cont’d) • Lesion mode (additional bolus of IV propofol first) : – 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 Results • Long term (years) success rates vary from 80 – 90% Complications • Corneal anesthesia / hyperesthesia – 13.7% • Dysesthesia in the treated area 5-7% • Masseter weakness 1-2% Morbidity & Mortality • Low morbidity • Can be performed on an out-patient basis • Mortality has not been reported 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 Maxillary or Mandibular Nerve Blocks Peripheral Nerve blocks • Supraorbital nerve block • Infraorbital nerve block • Mental nerve block Thank You