1338 - Oromandibular Dystonia: Diagnosis & treatment with phenol & bupivacaine injections

A 60-year-old woman was unable to open her mouth four years post-motor vehicle collision. Prior masseter muscle injections with onabotulinum toxin (BoNT) at doses of 150, 200, and 300 units provided no relief. Electromyography (EMG) identified continuous bursts in JC muscles at rest. Motor points (MP) in the masseter were stimulated at 0.7-1.0 mA, and 5% phenol was injected to treat JC dystonia. 0.1 ml phenol was injected at 5 sites. The left medial pterygoid was injected with 0.1 ml phenol when EMG bursts appeared. To rule out contractures, 0.5% bupivacaine was injected. The distance between patient’s teeth pre-injection was 5 mm; 15 mm post phenol; 28 mm post bupivacaine to the right medial pterygoid and temporalis muscles.

Discussions:

JC OMD may involve the bilateral masseter, temporalis, and medial pterygoid muscles; as such, dystonia must be identified with EMG. High doses of BoNT were not effective because dystonia existed in the temporalis and medial pterygoid. Furthermore, side effects with high doses of BoNT include 11% risk of dysphagia or dysarthria. Phenol MP injections can be performed with electrical stimulation for the masseter and temporalis muscles; the medial pterygoid muscles can be injected with phenol during bursts of EMG activity. Bupivacaine injections help rule out contractures.

Conclusions:

For JC OMD: EMG can identify dystonia for bilateral masseter, temporalis, and medial pterygoid muscles; injecting phenol into the masseter and temporalis muscle MP identified with electrical stimulation, and can be injected in the medial pterygoid muscles when EMG activity is pronounced. Bupivacaine injections serve a diagnostic role to rule out contractures, enhancing treatment precision.