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 pteryoid muscles, important masticatory muscles that is often hyperactive
in masticatory myofacial pain was not injected due to lack of palpable surface landmarks.
Ultrasound and 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 pteryoid.
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.