Therapeutic outcome of onabotulinum toxin type A in patients with upper limb spasticity

Abstract

Onabotulinum toxin type A treatment for post-stroke upper limb spasticity was investigated to contribute to establishing a standard dosage for Japanese patients. A total of 100 patients participated in the study. The outcome one month (33.6 ± 6.5 days) after the treatment was assessed by the Modified Ashworth Scale (MAS) to estimate the mean effect with a 10-unit injection and the standard dosage expected to improve MAS 1 degree. Average improvement of 263 muscles treated with a higher concentration of 10 units diluted in 0.2 ml was 0.207 ± 0.414 degrees, and that of 231 muscles treated with a lower concentration of 10 units in 0.4 ml was 0.149 ± 0.244 degrees without significant difference among diluted concentrations. To improve MAS 1 degree, 64.6 ± 31.1 units were required for the pectoralis major, 51.2 ± 21.3 units for the teres major, 111.7 ± 48.0 units for the biceps brachii, 51.6 ± 26.8 units for the brachioradialis, 54.1 ± 23.2 units for the brachialis, 34.4 ± 10.7 units for the pronator teres, 64.6 ± 27.9 units for the flexor carpi radialis, 62.4 ± 26.8 units for the flexor carpi ulnalis, 58.5 ± 31.1 units for the flexor digitorum profundus, 69.7 ± 35.1 units for the flexor digitorum superficialis, 24.6 ± 13.4 units for the flexor pollicis longus, and 15.6 ± 11.3 units for the adductor pollicis. Although the results shown here had no significant differences among concentrations, increasing the volume would disturb injection into small muscles, so we considered that a lower volume with a higher concentration should assure larger benefits. It is difficult to make effective injections into all spastic muscles within the officially permitted health insurance dosage of 240 units. Hence, it is advisable to increase the applicable upper limit based on safely achieved cumulative experience.