Table 2.

Change in muscle structure with botulinum neurotoxin A (BoNT-A).

First Author, Date	Population	Intervention	Assessment	Change in Muscle Structure with BoNT-A
Battaglia, 2021	53 patients with spastic hemiparesis following stroke	Patients had received toxin (dosing not reported), mean treatment cycles 6 (range 4-8). Time of stroke to first treatment mean 1.1 years	Structural ultrasonographic differences between medial gastrocnemius and soleus in affected and unaffected limb. Assessed: cross sectional area, muscle thickness, pennation angle and mean gray value	• No relevant influence of BoNT-A in contributing to tissue degeneration in spastic muscles
Mathevon, 2015	Systematic review of 21 articles (involving humans and animals)		Muscle measures (N=9) – balance, optical microscopy, histochemistry; Imaging (N=10) – B-mode ultrasound, MRI, elastography; Biomechanical measurements (N=3) – passive torque	• Muscle atrophy • Reduction in muscle thickness • Reduced pennation angle • Decreased fast type IIb fibers in favour of type IIa/slow type I • Myosin heavy chains reduced
Picelli, 2020	21 chronic stroke patients	BoNT-A injection into affected gastrocnemius medialis and lateralis (dose not reported)	Ultrasonographic characteristics at one-month post-injection (i.e. Muscle echo, thickness, pennation angle, achilles tendon thickness and hardness)	• No significant effect of BoNT-A injection on ultrasound characteristics
Schroeder, 2009	Two healthy adult male volunteers (47 and 31 years)	Single dose 74 units to lateral gastrocnemius (3 sites/muscle), Saline of 2 m: into contralateral limb lateral gastrocenmius	MRI imaging at 3, 6, 9 and 12 months after injection; Signal intensity alternations, cross-sectional area; Histopathology; Electron microscopy	• Denervation of neuromuscular junction on electron microscopy • High signal intensity pattern on STIR sequence in injected muscles persistent at 12 months post-injection. • Neurogenic fiber atrophy with some compensatory fiber hypertrophy
Valentine, 2015	10 patients with cerebral palsy (mean age 11.6 years)	Onabotulinum toxin in 2-4 sites per gastrocnemius muscle	Open muscle biopsy from medial gastrocnemius and vastus lateralis (control)	• Neurogenic atrophy in medial gastroscnemius between 4 months to 3 years post BoNT-A • Type I fiber loss with type II predominance