Radiofq rhizotomy (RFR)

Done under short- lived bolus IV anaesthesia (currently with propofol) sequentially repeated as necessary

The needle electrode is driven under fluoroscopy using the Hartel’s route through the foramen ovale, up to the immediate retrogasserian portion of the trigeminal nerve, namely the Triangular plexus where fibres have a somatotopic organization corresponding to the three trigeminal divisions.

The (5 mm ± 2) uninsulated extremity of the electrode should be placed in the fibres corresponding to the pain territory, under

A thermolesion between 65°C and 75°C is performed to achieve a preferential, if not a totally selective analgesic effect.

The lesion must not be made in the ganglion itself, but retrogasserian at the triangular plexus level to decrease the risk of trophic ulcerations by destroying the T cells of the ganglion

Paralysis of ipsilateral trigeminal motor root (e.g. pterygoids) is more common after PMC (usually temporary) than RFR, and so PMC should not be done if there is already contralateral paralysis from a previous procedure

(A-C); Landmarks and trajectory for Hartel’s transforamen ovale route (on right side). The entry point of the needle is on average at ±30mm from the labial commissure)±60mm from the middle of the intercommissural line). The foramen ovale is targeted by aiming (i) in lateral view, at 35mm anterior to the anterior wall of the external auditory meatus (tragus), (ii) in frontal view, the medial border of the pupil, (iii) the depth of the needle is guided by X-ray fluoroscopy to the level of the triangular plexus. Surgery should performed under fluoroscopy to be in accurate location (i.e., intersection of the clivus line and the upper petrous ridge).

(D-E): Schematic drawing and X-ray control (lateral view) for RF-Thermorhizotomy. Note the fibers from V1 division are located supero-medially, those corresponding to V3 division infero-laterally and those corresponding to V2 division between the two. The uninsulated tip of the electrode should be located in a somatotopic way according to the trigger-zone and pain territory. Location is guided by evoking paresthesia to electrical stimulation of the root while the patient as awake and/or eliciting trigemino-facial reflexes (especially the blink-reflex) in the corresponding facial muscles. Then thermolesion is done under brief general anesthesia to provide analgesia (tested by pinprick) without complete loss of tactile sensation of skin and mucosa and decrease in corneal reflex (tested by cottonoid contact).

(F-G): Schematic and X-ray control (lateral view) for balloon compression of the Gasserion ganglion and triangular plexus. Note the pear-shaped aspect of the inflated balloon, which testifies of the ideal location inside the Meckel’s cave and the trigeminal cistern.

(H-I): Schematic drawing and X-ray control (AP view) for Glycerol injection in the trigeminal cistern. An iodine contrast should ensure that needle is located within the trigeminal cistern; then the glycerol solution is injected with patient awake.

Difficulty to target the proper fibres and to achieve an optimal degree of hypoesthesia
Excessive lesioning may aggravate the background of burning pain in atypical TN and may also produce keratitis

Should the corneal reflex be lost, patients are informed to check their eye daily for redness and are encouraged to wear glasses when they go outdoors, especially if it is windy.
Anaesthesia dolorosa:

Numbness combined with persistent nerve damage pain
Most likely to occur after radiofrequency thermocoagulation (approximately 6 patients in every 1000 after RFT