Effect of Botulinum Toxin on Clonus: A Systematic Review.

[OBJECTIVE] To conduct a systematic review of the literature that examined the effect of botulinum toxin type A on clonus.

[DATA SOURCES] A literature search of multiple databases (PubMed, Cochrane, Google Scholar, Embase) was performed to identify articles published in English in the past 30 years (1986-2016).

[STUDY SELECTION] Two reviewers independently applied the following inclusion criteria: (1) any adult patients older than 18 years with upper motor lesion; (2) any location and duration of clonus; and (3) subjective and objective measurements of clonus tested at least 2 weeks after botulinum toxin injection.

[DATA EXTRACTION] Two reviewers independently extracted the data and assessed the methodological quality. A consensus method was used to solve disagreements.

[DATA SYNTHESIS] The systematic review resulted in 164 articles, of which 14 met the inclusion criteria: 3 were randomized controlled trials, 1 was nonrandomized, and 6 were case series and 3 case studies. All studies (181 patients) showed improvement in clonus: 6 of 14 results were statistically significant. Different scales were used for clonus measurement, such as clonus score, patient diaries, clonus spasm score, and electromyogram duration.

[CONCLUSIONS] Overall, there was preliminary evidence indicating improvement in clonus after botulinum injection. The major drawback with studies reviewed here was a large variation in the type of clonus assessment tools, which also lacked validity, reliability, and sensitivity to small changes in clonus.