A double-blind, controlled, randomized trial to evaluate the efficacy of botulinum toxin for the treatment of lumbar myofascial pain in humans.

BACKGROUND: Among all the causes of chronic low back pain, myofascial pain syndrome of the spinal stabilizer muscles is one of the most frequent, yet underconsidered sources of pain. The purpose of this prospective, randomized, double-blind, controlled trial was to evaluate the efficacy of type-A botulinum toxin (BTX-A) in relieving myofascial pain in patients experiencing mechanical low back pain due to bilateral myofascial pain syndrome involving the iliopsoas and/or the quadratus lumborum muscles.

METHODS: Each of the 27 enrolled patients received a bilateral, fluoroscopically guided injection in the affected muscle(s) to randomly deliver BTX-A in one side of the low back and a control drug (randomly constituted by NaCl 0.9% or bupivacaine 0.25%) in the opposite side. To evaluate the effects of treatment on daily life activities and psychologic status, 5 different questionnaires were administered (Hospital Anxiety and Depression scale [HAD-A and HAD-D], Lattinen, Oswestry, and Spielberger State-Trait Anxiety Index).

RESULTS: BTX-A injection did not significantly reduce visual analog scale scores more than treatment with NaCl or bupivacaine in the contralateral side; furthermore, the treatments administered did not result in a significant improvement of patients' daily life activities or psychologic status. Although a trend toward a decrease in postintervention visual analog scale scores could be recognized in all low back sides, this trend was significant only in the sides treated with BTX-A.

CONCLUSIONS: BTX-A seems to provide significant postintervention pain relief. However, considering its high cost and the small differences compared with control treatments, its use should be reserved only for patients with pain refractory to other invasive treatments.