IADR Abstract Archives
Temporo-Masseteric Nerve Block Impairs Efferent Conduction to Temporalis and Masseter
Objectives: The Twin block is a regional local anesthetic nerve block targeting the deep temporal and masseteric branches of the mandibular division of the Trigeminal Nerve, a mixed cranial nerve. The Twin block mediates expeditious and sustained pain relief in patients with chronic myofascial pain of masseteric origin, comparable to trigger point injections, for a period of over six months. Emerging data supports its efficacy in relieving acute myogenous face pain as well. It is important to elucidate whether sensory blockade by the local anesthetic injection alone can explain pain relief or whether motor blockade plays a role. The objective of this study was to characterize the Twin block by performing a Motor Nerve Conduction Study (NCS) and objectively assess the impact of the Twin block on the response to proximal nerve stimulation.
Methods: An injectable needle electrode was utilized both to deliver an electrical stimulus to the target site of the Twin block and to deliver 2% lidocaine with 1:100,000 epinephrine. Surface active, reference and ground electrodes were attached to the skin over the masseter, the mandible, and over the chin respectively to register compound muscle action potential (CMAP), before and after Twin block administration.
Results: Baseline delivery of a 6mA electric stimulus resulted in a typical biphasic response CMAP recorded over the masseter. Upon Twin block injection, the tracing showed complete conduction block with an absent response to the stimulation.
Conclusions: The Twin block local anesthetic injection resulted in a motor nerve block to the masseter muscle, consistent with the innervation of the masticatory muscles from the mandibular nerve branches being mixed nerves. This observation provides direct support and validates the technique for administering the Twin block. We speculate that pain relief from the Twin block results at least in part from its ability to block motor innervation to the masseter muscle.
Methods: An injectable needle electrode was utilized both to deliver an electrical stimulus to the target site of the Twin block and to deliver 2% lidocaine with 1:100,000 epinephrine. Surface active, reference and ground electrodes were attached to the skin over the masseter, the mandible, and over the chin respectively to register compound muscle action potential (CMAP), before and after Twin block administration.
Results: Baseline delivery of a 6mA electric stimulus resulted in a typical biphasic response CMAP recorded over the masseter. Upon Twin block injection, the tracing showed complete conduction block with an absent response to the stimulation.
Conclusions: The Twin block local anesthetic injection resulted in a motor nerve block to the masseter muscle, consistent with the innervation of the masticatory muscles from the mandibular nerve branches being mixed nerves. This observation provides direct support and validates the technique for administering the Twin block. We speculate that pain relief from the Twin block results at least in part from its ability to block motor innervation to the masseter muscle.