Changes in contractile properties of muscles receiving repeat injections of botulinum toxin (Botox)

The effects of botulinum toxin injection frequency on calf muscle growth in young children with spastic cerebral palsy: A 12-month prospective study

“…Our results provide some There were no significant differences in the baseline or follow-up measures for MG muscle volume, fascicle length or PCSA between the SCP1 and SCP3 groups D diplegia, H hemiplegia, L left, R right, GMFCS Gross Motor Function Classification System, AFO ankle-foot orthoses, NO no orthosis, HNGD hinged orthosis, SLD solid orthosis, B bilateral, Dose total BoNT-A dose (U) to the involved leg (SCP1 = 1 9 6 U/kg, SCP3 = 3 9 6 U/kg), PCSA physiological cross-sectional area, MAD median absolute deviation, r effect size a Significant within-group difference from baseline to 12 months follow-up (p \ 0.01) J Child Orthop (2013) 7:425-433 429 preliminary support for the view that repeated intramuscular injections may not have compounding effects on muscle growth in young children. These findings are in contrast to previous studies performed in animals reporting large reductions in muscle size and strength in response to BoNT-A injection [13]. The reasons for the disparity between our findings of muscle growth in young children and those of animal studies that indicate substantial muscle atrophy in response to lower relative BoNT-A dose are difficult to reconcile, but would be expected to be multifactorial.…”

“…Such concerns are, in part, based on animal studies that report reductions in the size and strength of the injected muscle [12][13][14], as well as adjacent muscles [15], following BoNT-A injection. For example, Fortuna et al [13] reported a 95 % reduction in rabbit hind limb muscle strength and up to 80 % reductions in muscle contractile material at up to 6 months post-injection. In the only human studies that have assessed muscle growth, BoNT-A injections have been shown to induce significant atrophy in the muscles of two healthy volunteers [16], as well as one child with spastic CP [17].…”

Is Botulinum Toxin Type A a Valuable Adjunct During Femoral Lengthening? A Randomized Trial

“…Using a pain questionnaire, each patient was asked to record pain VAS at each leg and to describe the location of the pain (anterior or posterior thigh). Because the BtX-A injection may cause muscle atrophy or a decrease in muscle mass [8,23], the maximal thigh circumference (in mm) was measured manually with a tape measure to investigate the changes of muscle mass. Then, the side-to-side differences were analyzed at each followup.…”

Atrophy and hypertrophy following injections of botulinum toxin in children with cerebral palsy

“…However, a more insidious and silent problem may be post-injection muscle atrophy, reported by Williams et al 2 In contrast to the alarming reports from animal studies, which include substantial reductions in muscle mass and force generation, 3 the results in children with CP are quite different and broadly reassuring. Williams et al report a study of 15 children, aged 5 to 11 years with spastic diplegia, at Gross Motor Function Classification System levels I and II, who received injections of BoNT-A to the gastrocnemius muscles in both lower limbs, and in some patients to the medial hamstring muscles when clinically indicated.…”