What is the role of botulinum toxin (BTX) in the treatment of low back pain?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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The use of BTX in the management of chronic low back pain remains controversial but has been investigated. In a randomized, controlled study involving 31 patients with chronic low back pain, Foster and colleagues studied the effect of 200 U of BTX-A (5 sites in the paravertebral levels L1-L5 or L2-S1, 40 U per site) compared with placebo injections. [68] Pain and extent of disability were noted at baseline and at 3 and 8 weeks using a VAS and the Oswestry Low Back Pain and Disability Questionnaire. At both 3 and 8 weeks, more patients who had received BTX injections (73.3% and 60%, respectively) experienced 50% or more pain relief compared with the placebo treated group (25% and 12.5%, respectively). At 8 weeks, less disability was noted in the BTX-treated group compared with the placebo-treated group.

Knusel and colleagues treated patients with low back pain associated and painful muscle spasm with different doses of BTXA and noted that only those treated with the highest doses (240 U) experienced significantly greater relief than placebo-treated patients. [69]

Two randomized, prospective studies, one double-blind and one open label, were performed to evaluate the long-term efficacy and safety of BTX-A in 31 and 75 patients with chronic low back pain, respectively. Both studies used a novel injection technique, with placement of 40-50 U of BTX-A by injection into the erector spinae muscles at each of 5 levels from L1-L5. [70] Jabbari reported significant (p < 0.05) reduction of pain intensity and improvement in performance of activities of daily living in 60% and 53% of the patients, respectively. A second study also demonstrated safety with repeated injection sessions over 14 months. The author suggests that BTX-A should be considered when treatment of low back pain fails other more standard management approaches.

A prospective study by Jabbari et al was also performed to study the short-term and long-term effects of BTX-A on refractory chronic low back pain. [71] Seventy-five patients received BTX-A injections into paraspinal muscles at 4-5 levels between L1-S1 unilaterally or bilaterally. Dose per site ranged from 40-50 U, whereas the total dose per session ranged from 200-500 U. Reinjection of BTX-A was performed at 4 months if pain returned over the study duration of 14 months. Outcome data collection included VAS scores, pain frequency (eg, number of pain days), and self-perceived functional status using the Oswestry Disability Questionnaire (ODQ).

Participants were assessed at baseline, 3 weeks, and then at 2, 4, 6, 8, 10, 12, and 14 months. Forty patients at 3 weeks (53%) and 39 patients at 2 months (52%) reported significant pain relief. Changes in VAS, ODQ scores, and pain frequency were consistent with patient improvements and were statistically significant when the 2-month data were compared with baseline at 2 months and then after each injection period (p < 0.005). Among initial responders, 91% continued to show improvement over the length of the study. Three patients (4%) experienced a probable adverse event consisting of a mild flulike reaction that lasted 2-5 days following an initial injection session. The number of responders and durations of chronicity is unclear. Any associated therapies were not noted. Therefore, agreeing with the authors when they suggest that a favorable initial response to BTX-A predicts subsequent responsiveness is difficult.

The same authors performed an open label prospective study on 60 patients with chronic low back pain. [72] Patients received 40-50 U per paraspinal level with multiple levels injected. A maximum dose was 500 units of BTX-A per an injection session. Study participants with a beneficial clinical response received a second treatment at 4 months. Pain and clinical status were assessed by VAS, modified OLBPQ, and a CLBPQ at baseline, 3 weeks, 2 months, 4 months, and 6 months after the first treatment. Participants included 18 women and 42 men, aged 21-79 years (mean, 46.6 y), with chronic low back pain over a mean duration of 9.1 years.

Significant improvement in back and radicular pain occurred at 3 weeks in 60% and at 2 months in 58% of the cohort. Again, the authors found that a beneficial clinical response to the first injection predicted the benefit of a second reinjection response, which was indeed measured determined to be 94%. A significant minority of patients had a sustained beneficial effect from the first injection at 4 months (16.6%) and 6 months (8.3%). Two patients experienced an adverse event described as a transient flulike reaction after the initial treatment. Ney et al concluded that BTX-A is a reasonable therapy for seeking improvement in patients with refractory chronic low back pain.

A beneficial clinical response can be predicted within the first 2 months following treatment. An early positive response from BTX-A treatment also predicts the high likelihood that the benefit is sustained with a second treatment. Furthermore, BTX-A demonstrates a low incidence of mild and transient side effects.

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