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 non invasive 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 (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 & 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 1 st sensory stimulation lesion  : retest with pin prick or – 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