Triceps Surae Muscle Characteristics in Spastic Hemiparetic Stroke Survivors Treated with Botulinum Toxin Type A: Clinical Implications from Ultrasonographic Evaluation

Abstract

Equinovarus foot is one of the most commonly spasticity related conditions in stroke survivors, leading to an impaired gait and poor functional performances. Notably, spastic muscles undergo a dynamic evolution following typical pathophysiological patterns. Botulinum Neurotoxin Type A (BoNT-A) is the gold standard for focal spasticity treatment, and ultrasound (US) imaging is widely recommended to guide injections and monitor muscle evolution. The role of BoNT-A in influencing muscle fibroadipose degeneration is still unclear. In this study, we analyzed medial gastrocnemius (MG) and soleus (SOL) US characteristics (cross-sectional area, muscle thickness, pennation angle, and mean echo intensity) in 53 patients. MG and SOL alterations, compared to the unaffected side, depend on the spasticity only and not on the BoNT-A treatment. In functionally preserved patients (functional ambulation classification, FAC > 3; modified Ashworth scale, MAS ≤ 2), the ultrasonographic changes of MG compared to ipsilateral SOL observed in the paretic limb alone seems to be due to histological, anatomical, pathophysiological, and biomechanical differences between the two muscles. In subjects with poor walking capability and more severe spasticity, such ipsilateral difference was found in both calves. In conclusion, BoNT-A does not seem to influence muscle degeneration. Similar muscles undergo different evolution depending on the grade of walking deficit and spasticity.

Assessing muscle architecture with ultrasound: implications for spasticity

“…In 2021, Battaglia et al investigated the effects of BoNT-A by conducting a cross-sectional observational study on 53 spastic hemiparetic stroke survivors. 37 They concluded that BoNT-A does not seem to influence muscle degeneration and that EI increase appears to be primarily related to spastic muscle evolution and functional impairment. Interestingly, in subjects with preserved walking capability and lower spasticity grade, an increase in EI of the medial gastrocnemius was observed in the paretic limb alone, but in patients with impaired gait and more severe spasticity, similar US changes were observed in both calves.…”

“… 75 Echogenicity can also be assessed qualitatively 36 , 44 ,49,67-71, 76 or quantitatively with software-generated gray-scale score and pixel analysis. 37 , 41 ,52,61,69, 75 Brightness or B-mode US can be used to visualize tissues with varying sonoacoustic properties; these properties in turn determine the number of echoes returning to the transducer. Structures will appear bright or hyperechoic when they are highly reflective of sound waves, whereas they will appear dark or hypoechoic when they reflect few sound waves to the transducer.…”

“… 33 Although these changes can be translated into a decrease in muscle thickness and an increase in EI on US images, its effects on long-term functional outcomes are unknown and researchers have yet to consistently show a deleterious effect of BoNT-A injections on the treated spastic muscle with this modality. 33 , 36 , 37 Histopathological studies are less consistent in humans, and outcomes of post-BoNT-A treated muscle biopsies are less predictable. 33 , 35 , 37 There is a need for more robust research in this area.…”

“… 33 , 36 , 37 Histopathological studies are less consistent in humans, and outcomes of post-BoNT-A treated muscle biopsies are less predictable. 33 , 35 , 37 There is a need for more robust research in this area.…”

Clinical efficacy of botulinum toxin type A in patients with traumatic brain injury, spinal cord injury, or multiple sclerosis: An observational longitudinal study

“…BoNT-A provides transient and reversible presynaptic chemodenervation on the neuromuscular plate. Moreover, BoNT-A shows an optimum safety profile and effectiveness in reducing pain, improving walking ability, mobility, nursing procedures, activities of daily living, and ultimately QoL ( 14 ), without significantly altering muscle quality ( 15 ). However, the current literature is mainly based on post-stroke spasticity (PSS) ( 16 , 17 ), whereas it is still limited in case of other clinical conditions related to non-stroke spasticity (NSS), such as SCI, TBI, and MS, even though spasticity is a major concern for rehabilitation in these patients.…”