Does Botulinum Toxin Treatment Affect the Ultrasonographic Characteristics of Post-Stroke Spastic Equinus? A Retrospective Pilot Study

Abstract

Equinovarus/equinus foot is a pattern most commonly treated with botulinum toxin type A in patients with post-stroke spasticity involving the lower limbs; the gastrocnemius is the muscle most frequently injected. Spastic equinovarus/equinus can present a mixture of conditions, including spasticity, muscle/tendon shortening, muscle weakness and imbalance. In this study, we wanted to determine whether botulinum toxin treatment affects the ultrasonographic characteristics of post-stroke spastic equinus. The same dose of AbobotulinumtoxinA was injected into the gastrocnemius medialis and lateralis of 21 chronic stroke patients with spastic equinus. Clinical (Ashworth scale and ankle range of motion) and ultrasound (conventional and sonoelastography) evaluation of the treated leg was carried out before and 4 weeks after injection. No significant effects of botulinum toxin treatment on the ultrasonographic characteristics of spastic equinus were observed. As expected, there were significant improvements in ankle passive dorsiflexion range of motion and calf muscle spasticity at 1 month after treatment. There was a direct association between Achilles tendon elasticity and calf muscle spasticity at baseline evaluation. Larger studies with a long-term timeline of serial evaluations are needed to further investigate the possible effects of botulinum toxin injection on spastic muscle characteristics in patients with post-stroke spasticity.

Assessing muscle architecture with ultrasound: implications for spasticity

“…In 2020, Picelli et al investigated the clinical and US architectural changes induced by BoNT-A in 21 post-stroke patients with spastic equinus. 36 At four weeks post-injection, they did not observe any significant effect of BoNT-A treatment on ultrasonographic characteristics (EI, muscle thickness, and pennation angle).…”

“…The US has become a popular tool that has risen to fulfill the need for a more reliable and accessible method to assess spastic muscle and its evolution over time ( Table 3 ). 12 Three main US modalities have been used to study spastic muscles: morphological changes, 36-52 sonoelastography,36,38,43,45,47,51,53-65 and echogenicity.36,37,44,49,52,66-71…”

“… 46 Given the high variability of each parameter, there are no established reference values, and the collected information requires manipulations to be interpreted. 36 , 38-52 , 72 …”

“… 73 , 74 It may be used to estimate muscle strain qualitatively 47 , 51 , 53-57 or quantitatively with shear wave elastography. 36 , 38 ,43,45,54, 58-63 A systematic review and metaanalysis reported that US elastography has moderate reliability when used in neurological populations. 74 Moreover, its usage requires expensive software, and highly qualified technicians, and does not assess muscle echotexture when we know there is growing interest regarding differentiation of EI.…”

Shear Wave Velocity to Evaluate the Effect of Botulinum Toxin on Post-Stroke Spasticity of the Lower Limb

“…Ultrasonographic characteristics (i.e., muscle echo intensity, muscle thickness, posterior pennation angle, Achilles tendon thickness, and sonoelastography) have been used to evaluate effect of BoNT-A treatment with post-stroke spasticity [ 23 , 32 , 33 ]. Picelli et al evaluated Achilles tendon stiffness by sonoelastography before and after BoNT-A treatment at approximately 1 month interval, but found no significant changes [ 33 ]. Previous studies in post-stroke patients have reported a significant reduction of SWV in Biceps brachii of patients with post-stroke upper limb spasticity after BoNT-A injection [ 25 , 31 ].…”