Botulinum toxin (BTX, botox) injections benefit patients with localized but not referred myofascial pain in the temporomandibular (TMJ) area.
Muscular pain in the head and neck region, particularly in the temporo-mandibular joint (TMJ) area, is a potentially debilitating condition. Numerous disorders (infection, injury, poor dentition, among others) can cause localized inflammation of the muscles involved in chewing or mastication; and when these conditions become chronic in nature, muscles can spasm and further magnify the pain experienced. Eating becomes a painful process; in some instances, the mere act of opening or closing one’s mouth can be quite excruciating. When this inflammation goes beyond the muscle and begins to involve the surrounding fibrous capsule (fascia), it is classified as myofascial.
Physicians have traditionally treated myofascial TMJ pain conservatively, by managing the painful symptoms through non-surgical means while trying to identify and treat the root cause of the condition. Oral pain relievers and muscle relaxants are usually prescribed as first-line therapies, often combined with other interventions like relaxation therapy or lifestyle changes. Unfortunately, a significant portion of patients remain unresponsive to these strategies, prompting the search for more radical approaches.
Produced by the bacteria species Clostridium botulinum, the botulinum toxin (BTX) acts on the muscle tissue by interfering with the release of the neurotransmitter acetylcholine. Deprived of acetylcholine, the muscle cannot contract and relaxation or even paralysis result. BTX is popularly used to remove wrinkles and furrows in the face, which are essentially due to contracting forehead or jowl muscles.
By inducing relaxation, BTX may limit the muscle spasms associated with TMJ myofascial pain. However, previous research has yielded conflicting evidence regarding the use of BTX injection for the treatment of myofascial pain. A recent study attempts to clarify this.
In a retrospective study published in the International Journal of Oral and Maxillofacial Surgery, 25 patients with TMJ chronic myofascial pain were followed over a 2-year period. Treatment for their TMJ myofascial pain consisted of localized BTX injections to muscle areas identified as most painful. Evaluation of pain (or its relief) over the course of treatment was recorded. The results suggest that BTX was indeed effective in alleviating pain over these most tender muscle areas; but for patients suffering from referred pain, where the reported symptoms extended beyond the involved muscles, injections yielded little value.
The results of the study may explain the discrepancies in reported success of BTX therapy in the head and neck area. More significantly, the study shows that the distinction between localized and referred pain may be crucial in determining whether treatment might be of value.
Pain management remains a very challenging frontier for clinicians, but identifying which patients can benefit from particular modes of therapy is indeed significant. This provides an additional treatment option for some, while highlighting the value of targeted therapies and the need for additional research aimed at identifying new treatments.
Written By: Jay Martin, M.D.