Efficacy of Botulinum Toxin Versus Lidocaine in Treating Masticatory Myofascial Face Pain Using Ultrasound and EMG Guided Techniques

Botulinum toxin-A (BTX-A) prevents the release of acetylcholine in presynaptic terminals of the neuromuscular junction. It has been proposed to be effective in spastic conditions of the head and neck including oromandibular dystonias, bruxism, and muscular hypertrophy (1,2,3,4). However, only one randomized, double-blinded, placebo controlled trial has been completed involving 20 patients demonstrating both objective and subjective improvement in the BTX-A treated group over those treated with saline at one week, one month, and six months (5).

Currently, in most orofacial pain practices, when the diagnosis of masticatory myofascial pain in the head region is made, patients are treated with a standard myofascial protocol. This protocol involves stretching, application of moist heat, spray and stretch, and lidocaine trigger point injections into the masticatory muscles. This is considered the standard of care among most orofacial pain practioners.

There have been no randomized, double-blinded, head-to-head trials comparing BTX-A injections to lidocaine injections in the treatment of masticatory myofacial pain. Moreover, in all studies, muscles were targeted using surface landmarks with no confirmatory tests to guarantee the medication was administered to the intended muscle. In previous studies, the medial and lateral pterygoid muscles, important masticatory muscles that is often hyperactive in masticatory myofacial pain was not injected due to lack of palpable surface landmarks. Ultrasound and electromyography (EMG) guidance will help us locate these muscles.

The purpose of this study is to objectively measure functional improvement in patients with masticatory myofascial pain injected with lidocaine versus BTX-A. A pilot study enrolling 20 patients is proposed. 20 patients will be randomized to receive either BTX-A or lidocaine injections into the bilateral temporalis, masseter, and medial and lateral pterygoid. Objective and subjective clinical parameters will be measured. These include pain at rest and with chewing, maximum non-assisted and assisted mouth opening, protrusive and laterotrusive jaw movements, subjective efficacy of treatment, and side-effects of treatment. Patients will be assessed at baseline, one week, one month, and three months after the procedure.