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

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:

• V1: Baseline visit, week 0
• V2: Injection visit, week 5-7
• V3: Follow-up visit, week 10-12:
• 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.

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.