gms | German Medical Science

Objective: Radiofrequency thermocoagulation (RT) for the treatment of trigeminal neuralgia (TN) is a well-established technique. This procedure is usually performed in awake patients to localize the involved trigeminal branches. It is often a painful experience for the patient, which diminishes the reliability of the patient’s response. Therefore, we applied a sleep-awake technique with placement of the RT canula under intraoperative monitoring, which might be a good alternative. We present our case series to investigate the feasibility und outcome of this technique.

Methods: We reviewed five cases of patients suffering from pharmacoresistent TN, whopreviously underwent a microsurgical decompression of the trigeminal nerve at least once. For RT, the patient underwent a short general anesthesia using a laryngeal tube in the supine position. Pairs of EMG-needles were implanted subdermally near the supraorbital, infraorbital, and mental foramina. Insertion of the radiofrequency cannula was done using typical anatomical landmarks under x-ray guidance. The trigeminal nerve roots were stimulated through the foramen ovale with the tip of the radiofrequency canula at 0.5 V, and antidromic sensory evoked responses were recorded from the 3 divisions of the trigeminal nerve as well as the mandibular muscle in the face. Repositioning of the cannula was performed until the desired nerve divisions could be stimulated. Afterwards, anesthesia was stopped, the laryngeal tube was removed and the stimulation was repeated (0.05-0.15V) to obtain a verbal response from the patient. Lesioning was performed with radiofrequency for 90 seconds at an intensity of 75°C.

Results: Antidromic sensory evoked potentials of all trigeminal nerve branches could be obtained in all five patients and repositioning of the cannula under stimulation enabled localizing of the desired branches (V2 and V3 in 3 patients and V2 in 2 patients). After awaking, patients confirmed the effect of stimulation at the face. Radiofrequency lesioning resulted in an immediate pain relief in all patients. Temporary hypalgesia in the territory of the lesioned branches occurred in all patients, but recovered during hospital stay.

Conclusion: In TN, RT of trigeminal nerve under neuromonitoring guidance in a sleep-awake modus is feasible and could be an alternative for uncooperative, anxious or even all patients. Antidromic sensory evoked potentials allowed an accurate localization of the involved branches of the trigeminal nerve.