Motor endplate‐targeted botulinum toxin injections of the gracilis muscle in children with cerebral palsy

Abstract

Aim Intramuscular botulinum toxin‐A (BoNT‐A) injections reduce spasticity by blocking neurotransmission at the motor endplate (MEP). The goal of this study was to assess the reduction in spasticity achieved by injecting BoNT‐A at different sites of the gracilis muscle. Method Thirty‐four gracilis muscles, in 27 children (10 females and 17 males, mean age of 8.6y [SD 2.5y]) with spastic cerebral palsy (unilateral and bilateral, Gross Motor Function Classification System [GMFCS] levels I–IV), were randomly assigned to one of two groups. In one group BoNT‐A was injected proximally (at a site 25% of the distance from the pubic tubercle and the medial epicondyle) and in the other it was injected at the MEP zones (half of the dose was administered at 30% of this distance and half at 60%). Spasticity was assessed before and after BoNT‐A injection using simultaneous measurements of surface electromyography (sEMG) and angular velocity during passive muscle stretch applied at different velocities. The primary outcome measure included the velocity‐dependent change in average root mean square electromyography (RMS‐EMG). Secondary outcome was assessed with the Modified Ashworth Scale (MAS) and Modified Tardieu Scale (MTS). Results Spasticity decreased more in MEP‐targeted muscles than in proximally injected muscles, as demonstrated by a larger reduction in average RMS‐EMG values (p=0.04), though this difference was not found with the MAS or MTS. Interpretation The results suggest that BoNT‐A injection of the gracilis at sites with a high concentration of MEPs is effective at reducing spasticity. These preliminary findings should be confirmed by larger studies. In the case of long muscles, such as the gracilis, the injection site is important.

Botulinum Toxin: Techniques Within Pediatric Physiatry

“…In terms of the technique performed to identify the site in the muscle for injection, 2 approaches are described in the literature: isolating the motor point or distributing the pharmaceutical throughout the muscle . Based on the results of this survey, the majority of pediatric physiatrists are distributing onabotulinumtoxinA throughout the muscle with a much smaller percentage trying to inject at the motor endplate or motor point.…”

Safe Needle Insertion Locations for Motor Point Injection of the Triceps Brachii Muscle: A Pilot Cadaveric and Ultrasonography Study

“…The area where the intramuscular endings are most dense was defined as the www.e-arm.org MoEP, the midpoint between the PLP and DLP, as mentioned in previous studies. Accurate administration of botulinum toxin with respect to the MoEPs is crucial for the best efficacy in the treatment of spasticity [8][9][10][11].…”

“…It is important to inject botulinum toxin at exact motor end plates to maximize its chemodenervation effect [7]. The efficacy of botulinum toxin injections to control spasticity was maximized by injection at a motor point, specifically where the zones of the intramuscular endings are reported to be most dense, known as the motor endplate zones (MoEPs) [8][9][10][11]. Triceps brachii muscles are especially associated with elbow extensor spasticity more than the anconeus muscle [12].…”

Experience of the Type a Botulinum Toxin Type (Onabotulinumtoxina) Drug in Treatment of Cerebral Palsy Patients

“…В последние годы все больше обсуждается вопрос о необходимости проведения инъекций препаратов БТА в те зоны мышцы, в которых имеется наибольшее скопле-ние двигательных концевых пластинок [39,40]. Выполнение инъекций именно в эти зоны на примере таких мышц, как тонкая (m. gracilis) и подвздошно-пояс-ничная (m. ilio-psoas), показало более высокую эффектив-ность БТА.…”

“…Сегодня известно точное расположение двига-тельных концевых пластинок большинства мышц-мишеней для БТА. Эти данные представлены в многочис-ленных публикациях [39][40][41][42]. Применение этого подхода в широкой клинической практике может позволить не только использовать более низкие дозы для каждой мышцы-мишени и тем самым уменьшить стоимость лече-ния, но и существенно снизить риски развития нежела-тельных побочных явлений.…”