Myofascial Pain and Botulinum Toxin

Myofascial pain syndrome (MPS) involves painful muscles with increased tone and stiffness. These muscles contain trigger points—tender nodules—and trigger point injections have been widely suggested as a treatment for MPS.

Botulinum toxin type A (BXTA) acts as a neuromuscular blockade, and affects human muscle tissue for 3 to 4 months. This team of researchers¹ compared the efficacy of BXTA to a normal saline solution when injected into the trigger points of MPS patients.

Thirty-three patients were involved in the study, and neck pain decreased equally when injected with either BXTA or saline. Within one week, the authors tested and saw a quick response to treatment. Yet after one injection, neither group was completely asymptomatic. 39% of the BXTA group decided to receive a second injection, and after the second injection, the authors found that 3 out of 4 patients experienced clinical improvement. The authors write:

"These results may indicate that follow-up injections of BXTA may alleviate TP pain, and the failure to find a significant BXTA effect may have resulted from the use of insufficient dosages. Further investigation using with higher dosages and sequential injections is needed to resolve this issue."

Side effects of the injections were noted. Two patients reported arm heaviness and numbness, which vanished after the first week. Five patients reported that the pain simply shifted to the opposite side of the body or to another muscular area, indicating that the treatment was simply treating the symptoms of the condition.
In an editorial following the study Fanciullo² critiques this study and the possible applicability of BXTA:

"Wheeler et al provide a useful trial, testing and comparing BTXA and saline trigger-point injections. They have shown in their pilot study that there is no statistically significant benefit of BXTA over placebo. Botulinum toxin type A is an extremely expensive intervention. One hundred units of BXTA at our institution cost $335.00, and the charge to the patient is $670.00. Despite its safety, BTXA, to date, offers no proven advantage over injection with local anesthetics or even dry needling. Although we should not close the door on the use of BTXA for MPS, currently there are no good supportive data to justify the routine use of this extremely expensive agent in the treatment of patients with MPS."

Wheeler AH, Goolkasian P, Gretz SS. A randomized, double-blind, prospective pilot study of botulinum toxin injection for refractory, unilateral, cervicothoracic, paraspinal, myofascial pain syndrome. Spine 1998; 23(15): 1662-1667.
Fanciullo GJ. Point of view. Spine 1998: 23(15): 1667.

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