Comparison of Phenol Block and Botulinus Toxin Type A in the Treatment of Spastic Foot After Stroke: A Randomized, Double-Blind Trial.

Kirazli Y, On AY, Kismali B, Aksit R (Department of Physical Therapy and Rehabilitation, Ege University Medical School, Izmir, Turkey), Am J Phys Med Rehabil. 1998;77:510-515.

This randomized, double-blind study compared the short-term effects (at 2, 4, 8, and 12 weeks) of phenol and botulinus toxin type A (BOTOX-A) injections on plantar-flexor spasticity in a small sample of 20 subjects. Patients were included in the study if they had had a cerebrovascular accident at least 6 months prior to start of the study.

As the authors explained, the mechanisms of action of these 2 agents differ. Phenol is injected into the nerve and supposedly causes nonselective denaturation of proteins, which ultimately results in the destruction of gamma efferent fibers. Loss of gamma efferent activity reduces spasticity by decreasing the sensitivity of the muscle spindle. Accuracy of the injection is very important. In this study, 30% of the subjects who had been injected with phenol developed dysesthesia that was uncomfortable enough to reduce walking for 2 to 4 weeks. Two patients who were obese developed peroneal nerve palsy, which was possibly the result of the injection hitting the sciatic nerve before its bifurcation.

Botulinus toxin, on the other hand, reduces spasticity by interfering with release of acetylcholine at the neuromuscular junction, thus causing muscle weakness. In this study, BOTOX-A was injected into several sites of the posterior calf muscles proximal to motor points. The subjects in the BOTOX-A injection group showed no significant adverse side effects.

Subjects had received physical therapy prior to the study but did not have formal physical therapy sessions during the course of the study other than continuing with home programs.

Outcomes measured in this study included active and passive range of motion, Ashworth score (for dorsiflexion and eversion), ambulation velocity over a distance of 25 ft, clonus duration, and score on the Global Assessment of Spasticity Scale (patient's subjective response to treatment).

Results indicated that the Ashworth dorsiflexion scores improved significantly from baseline in both groups at weeks 2, 4, and 8. The amount of improvement, however, was significantly greater in the BOTOX-A group compared with the phenol group at weeks 2 and 4. Ashworth scores for eversion improved significantly from baseline at weeks 2 and 4 in only the BOTOX-A group, and the improvement at week 2 was significantly better in the BOTOX-A group compared with the phenol group. Ambulation velocity in the BOTOX-A group increased significantly from baseline at each follow-up visit, whereas ambulation velocity in the phenol group did not change significantly from baseline at any follow-up measurement. Clonus duration was significantly greater in the BOTOX-A group compared with the phenol group at week 2. Global assessment scores were significantly better in the BOTOX-A group compared with the phenol group at weeks 2, 4, and 8.

The authors concluded that both treatments were effective in reducing plantar-flexor spasticity. Treatment with BOTOX-A, however, generally produced better results than a phenol block at the 2- and 4-week follow-up measurements. The authors also noted that further study is needed to assess the long-term effects of these treatments on functional gains in patients who exhibit moderate to severe spasticity following a stroke.

Renate Powell, PT Portland, Ore