Pilot Study on Muscle, Tendon, and Neural Changes Post-Botulinum Toxin Injections in Post-stroke Spastic Equinovarus

Exploratory, Longitudinal Study to Define Changes in Muscle, Tendon and Neural Properties After Botuline Neurotoxin Type A (BoNT) Treatment of Spastic Equinovarus in First-ever Stroke Patients: a Pilot Study.

Poststroke spasticity significantly impairs function, particularly through the development of pes equinovarus. Botulinum toxin A (BoNT) injections into the medial gastrocnemius (MG) are a first-line treatment. Treatment outcomes and long-term responses to interventions can vary significantly between individual patients. Additionally, there is increasing concern about potential adverse effects on muscle morphology. Further research is essential to optimize treatment strategies and improve long-term outcomes in this population. Three-dimensional freehand ultrasound (3DfUS) and instrumented spasticity assessment (ISA) are two recently developed techniques that enable the evaluation of changes in muscle, tendon, and neural properties following BoNT injections for post-stroke spastic equinovarus. These methods hold promise for providing new insights into treatment effects. Before implementing these techniques in large-scale studies, a pilot study is required for accurate sample size calculations for a prospective observational study. This study includes a protocol for a non-blinded, non-randomized open-label longitudinal pilot study. The study was approved by the European Medicines Agency ( EU CT Number 2024-513158-32) by the University Hospitals Leuven ethical committee (ID S68672). Standard deviations and effect sizes of outcome measures obtained longitudinally with 3DfUS and ISA before and after BoNT injection into MG will inform sample size calculations for future research.

Study Overview

• Status: Recruiting
• Conditions: Stroke; Spasticity; Equinovarus Foot
• Intervention / Treatment: Diagnostic test: threedimensional freehand ultrasound and instrumented spasticity assessment

Detailed Description

TRIAL RATIONALE:

To conduct a pilot study as guidance for a future observational study to evaluate changes in muscle, tendon and neural properties after botulinum neurotoxin-A (BoNT) treatment of spastic equinovarus in first-ever stroke patients by using Three Dimensional freehand Ultrasound (3DfUS) and Instrumented Spasticity Assessment (ISA) with the aim of optimizing treatment algorithms and long-term response in this population.

TRIAL DESIGN:

Non-blinded, non-randomized open label, longitudinal pilot interventional clinical trial.

In total, 4 visits will be organised:

1. V1: Baseline visit, week 0
2. V2: Injection visit, week 5-7
3. V3: Follow-up visit, week 10-12:
4. V4: End of study visit , week 18-30

4 visits are organized according to the biological functioning of BoNT. These 4 visits also correspond to the standard clinical visits as they currently proceed when a patient is treated with BoNT. At baseline visit (week 0) and injection visit (week 6) we do not expect any changes in outcome parameters since no BoNT has been injected yet. The effect of BoNT has peak effects after 4-6 weeks and a duration of action between 2 and 6 months. At follow-up visit (week 10-12) and end-of-study visit (when BoNT is clinically elaborated, week 18-30) we expect corresponding changes in outcome parameters, respectively.

At each visit, 3DfUS measurements and ISA measurements will be performed on two muscles of both legs: 1) medial gastrocnemius muscle and 2) tibialis anterior muscle. The majority of US literature in the lower limb has focused on medial gastrocnemius. Additionally, these muscles are obvious candidates because of their functional importance in locomotion. Moreover, the medial gastrocnemius is a frequently injected muscle with BoNT, whereas tibialis anterior muscle is not. From a methodological perspective, both medial gastrocnemius and tibialis anterior are superficial and can be easily tracked by means of conventional US probes and EMG electrodes.

During visit 2, a pregnancy test will be conducted prior to the injection of Botulinum toxin. If the test is positive, the study will be discontinued, and the patient will not be treated with Botulinum toxin A.

Total duration of one visit will be 1.5 to 2 hours. All measurements of one visit take place on the same day. Measurements will be performed at the University Hospital Leuven.

For this study, stroke patients treated with BoNT for spastic equinovarus will be included. In particular stroke patients are patients that are being treated at the University Hospital, Leuven. The annual number of stroke patients seen in UZ Leuven is approximately 600 per year.

• Study Type: Interventional
• Enrollment (Estimated): 12
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Fabienne Schillebeeckx, MD, PI; Phone Number: 0032 - 16338714; Email: fabienne.schillebeeckx@uzleuven.be
• Study Contact Backup: Name: Fabienne Schillebeeckx, MD,PI; Phone Number: 0495100300; Email: fabienne.schillebeeckx@uzleuven.be

Study Locations

• Belgium
  • Leuven, Belgium, 3000
    • Recruiting
    • UZ Leuven
    • Contact: Fabienne Schillebeeckx, MD, PhD; Phone Number: 0495100300; Email: fabienne.schillebeeckx@uzleuven.be

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Voluntary written informed consent of the participant or their legally authorized representative has been obtained prior to any screening procedures
• 2. At least 18 years of age at the time of signing the Informed Consent Form (ICF)
• 3. Use of highly effective methods of birth control; defined as those that, alone or in combination, result in low failure rate (i.e., less than 1% per year) when used consistently and correctly; such as implants, injectables, combined oral contraceptives, some IUDs, true sexual abstinence (i.e. refraining from heterosexual intercourse during the entire period of risk associated with the Trial treatment(s)) or commitment to a vasectomised partner.
• 4. Pes equinovarus due to spasticity
• 5. Clinical need for BoNT injection at the lower leg
• 6. Any previous injection of BoNT into the muscles to be investigated was at least 3 months ago
• 7. First-ever, unilateral stroke

Exclusion Criteria:

• Musculoskeletal or other neurological problems affecting the lower limb
• Presence of spinal cord pathology that could lead to spasticity, ataxia, dystonia
• Cognitive problems that impede measurements
• Severe co-morbidities
• Irritated skin or open wounds where ultrasound will be placed
• Pregnancy
• Profound atrophy of the muscles in the target area(s) of injection
• Participation in an interventional Trial with an investigational medicinal product (IMP) or device
• The effect of botulinum toxin A can theoretically be potentiated by agents affecting neuromuscular transmission, such as aminoglycoside antibiotics (e.g., gentamicin, tobramycin), lithium salts, cholinesterase inhibitors and tubocurarine-like muscle relaxants ((cis)atracurium, rocuronium, suxamethonium, vecuronium). Therefore, patients on whom these medications are started during the course of the trail will be excluded.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Other: stroke patients treated with Botulinum toxine injections for spastic equinovarus; This study involves a single-arm, exploratory, longitudinal design focusing on first-time stroke patients with spastic equinovarus deformity. Participants will receive Botulinum Neurotoxin Type A (BoNT-A) injections targeting medial and lateral gastrocnemius muscle as well ass soleus muscle. The intervention aims to assess changes in muscle, tendon, and neural properties before and after treatment by using instrumented spasticity assessment and threedimensional freehand ultrasound

Diagnostic test: threedimensional freehand ultrasound and instrumented spasticity assessment; To conduct a pilot study as guidance for a future observational study to evaluate changes in muscle, tendon and neural properties after botulinum neurotoxin-A (BoNT) treatment of spastic equinovarus in first-ever stroke patients by using Three Dimensional freehand Ultrasound (3DfUS) and Instrumented Spasticity Assessment (ISA) with the aim of optimizing treatment algorithms and long-term response in this population.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
sample size calculation	To estimate the number of subjects to calculate an appropriate sample size for assessing changes in muscle, tendon and neural properties after BoNT treatment of spastic equinovarus in first-ever stroke patients by using 3DfUS and ISA in a future observational study. To calculate standard deviation and effect sizes of outcome measures obtained with 3DfUS and ISA in these patients.	2 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
muscle changes	Secondary outcome parameters measured by 3DfUS include muscle belly length for medial gastrocnemius muscle	2 years
neural changes	Secondary outcome parameters measured by ISA for slow stretch measured by ISA : maximal velocity of performance (Vmax [deg/s])	2 years
functional changes	Medical baseline data including age, gender, body mass index, time since stroke, stroke etiology, National Institute Health Stroke Scale [15], affected side, oral medication and adverse events will be collected at each visit from the patients medical file as they are part of standard of care:	2 years
muscle changes	Secondary outcome parameters measured by 3DfUS include tendon length for medial gastrocnemius muscle	2 years
muscle changes	Secondary outcome parameters measured by 3DfUS include mid-belly cross-sectional area for medial gastrocnemius muscle	2 years
muscle changes	Secondary outcome parameters measured by 3DfUS include muscle belly length for tibial anterior muscle	2 years
muscle changes	Secondary outcome parameters measured by 3DfUS mid-belly cross-sectional area for tibial anterior muscle	2 years
muscle changes	Secondary outcome parameters measured by 3DfUS include mean Echo Intensity for tibial anterior muscle	2 years
muscle changes	Secondary outcome parameters measured by 3DfUS include mean Echo Intensity for medial gastrocnemius muscle	2 years
neural changes	Secondary outcome parameters measured by ISA for slow stretch measured by ISA : range of motion [deg]	2 years
neural changes	Secondary outcome parameters measured by ISA for slow stretch measured by ISA: stiffness [Nm/deg]	2 years
neural changes	Secondary outcome parameters measured by ISA for slow stretch measured by ISA work [J] (area under the power-time curve).	2 years
neural changes	Secondary outcome parameters measured by ISA from the fast stretch: maximal velocity of performance (Vmax [deg/s])	2 years
neural changes	Secondary outcome parameters measured by ISA from the fast stretch: joint angle of catch [deg]	2 years
neural changes	Secondary outcome parameters measured by ISA from the fast stretch: angle of EMG threshold [deg]	2 years
neural changes	Secondary outcome parameters measured by ISA from the fast stretch: intensity of catch (power [W]; torque times angular velocity).	2 years
functional changes	Modified Asworth Scale	2 years
functional changes	Tardieu scale	2 years
functional changes	Barthel Index	2 years
functional changes	Functional Ambulation Categories	2 years
functional changes	the Rivermead Mobility Index	2 years
functional changes	Functional Independence Measure	2 years
functional changes	Fugl-Meyer scale	2 years
functional changes	Modified Rankin Scale	2 years
functional changes	5 Meter Timed Walking Test	2 years
functional changes	Motricity Index	2 years
functional changes	Five-Times Sit-to-Stand Test	2 years
functional changes	Gait analyses	2 years

Collaborators and Investigators

• Sponsor: Universitaire Ziekenhuizen KU Leuven
• Investigators: Principal Investigator: Fabienne Schillebeeckx, MD, UZ Leuven campus Pellenberg, secretariaat fysische geneeskunde en revalidatie blok 5

Publications and helpful links

General Publications

• Hanssen B, De Beukelaer N, Schless SH, Cenni F, Bar-On L, Peeters N, Molenaers G, Van Campenhout A, Van den Broeck C, Desloovere K. Reliability of Processing 3-D Freehand Ultrasound Data to Define Muscle Volume and Echo-intensity in Pediatric Lower Limb Muscles with Typical Development or with Spasticity. Ultrasound Med Biol. 2021 Sep;47(9):2702-2712. doi: 10.1016/j.ultrasmedbio.2021.04.028. Epub 2021 Jun 8.

Study record dates

Study Major Dates

• Study Start (Actual): May 2, 2025
• Primary Completion (Estimated): May 31, 2027
• Study Completion (Estimated): December 31, 2027

Study Registration Dates

• First Submitted: December 27, 2024
• First Submitted That Met QC Criteria: January 3, 2025
• First Posted (Actual): January 10, 2025

Study Record Updates

• Last Update Posted (Actual): April 29, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: stroke; Botulinum Toxins; Medial Gastrocnemius Muscle; Skeletal muscle morphology; muscle composition
• Additional Relevant MeSH Terms: Neurologic Manifestations; Musculoskeletal Diseases; Cerebrovascular Disorders; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Vascular Diseases; Cardiovascular Diseases; Muscular Diseases; Muscle Hypertonia; Neuromuscular Manifestations; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Muscle Spasticity; Stroke
• Other Study ID Numbers: S68672; Trial number 2024-513158-32-00 (Other Identifier: European Medicines Agency)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No