Mandibular nerve block for peri‐operative pain relief using a peripheral nerve stimulator

Mandibular nerve block provides good peri-operative pain relief for mandibular and intra-oral surgery. We report the use of a peripheral nerve stimulator for mandibular nerve block by the lateral extra-oral route in patients undergoing surgery over the mandibular region. A 14-year-old, 40-kg female, with congenital micrognathia and unilateral temporomandibular joint ankylosis, was scheduled for corrective osteotomy and distraction of the left mandible under general anaesthesia. Following written informed consent for the block, we administered 1 mg midazolam and 80 μg fentanyl intravenously. Under strict asepsis and after infiltration with lidocaine 1%, we inserted a 22-G, 10-cm insulated short-beveled needle (Stimuplex A, B. Braun, Melsungen, Germany), with a guard at 6 cm, via the lateral extra-oral approach [1]. We set the initial current at 1.3 mA, with a frequency of 2 Hz (Stimuplex DIG, B. Braun, Melsungen, Germany). We placed the ground electrode on the anterior border of the ipsilateral masseter. Once we achieved a motor response from the temporalis and masseter muscles resulting in a jaw jerk, we reduced the current gradually to a threshold of 0.6 mA. After negative aspiration and confirming loss of motor response on initial injection, we slowly injected 5 ml bupivacaine 0.25% with fentanyl 50 μg. We then induced general anaesthesia and the surgery proceeded uneventfully. We did not administer further analgesics during the three-hour intra-operative period. Postoperatively, the patient’s visual analogue score remained below 3 out of 10 for the next eight hours. We have since performed the block in this manner in three further patients with similar efficacy. Ptosis, due to involvement of the facial nerve, was noted in one of these, which resolved spontaneously over the next 24 hours. Blockade of the mandibular nerve by the extra-oral landmark approach has a reported success rate of approximately 90% [2, 3]. Failure may be due to poor operator technique or anatomical variations [4, 5]. The use of other methods of nerve location such as ultrasound or fluoroscopy would be technically difficult in the shadows of the bone surrounding this deep nerve. Although a motor response from the masseter or the temporalis muscle resulting in a jaw jerk is an easily visible endpoint of mandibular nerve stimulation, the use of a peripheral nerve stimulator to block the mandibular nerve in humans has not been described. We would recommend the use of nerve stimulation during mandibular nerve block to improve accuracy and possibly to reduce the risk of intravascular and intraneural placement.