Objectives Spasticity is a sensorimotor disorder resulting from upper motor neuron lesions. Conventional pharmacological and non-pharmacological treatments have been used for many years; however, they have notable limitations, including but not limited to the need for repeated botulinum toxin injections and surgical risks associated with more invasive approaches. These challenges highlight the need for a safer, longer-lasting treatment option. Emerging nerve-targeted interventions such as cryoneurolysis offer selective, reversible, and longer-lasting reductions in hypertonia. As an emerging field, there is a lack of educational materials to guide new adopters of this technique. In this study, we propose a precise and safe approach for identifying the intramuscular nerve branches in the legs to perform cryoneurolysis to manage spasticity. The objective is to describe the anatomical and sonoanatomical relevance of intramuscular nerve branches of the legs—particularly of the tibial nerve and common peroneal nerve—in guiding cryoneurolysis for spasticity management. Design A comprehensive literature review was conducted on the anatomy of the tibial nerves and common peroneal nerves of the leg, emphasizing intramuscular branches relevant to spasticity in the leg muscles. Ultrasound-guided techniques, procedural safety considerations, and recent evidence on cryoneurolysis were reviewed to evaluate clinical applications and outcomes. Results The tibial nerve and its motor branches—to the gastrocnemius, soleus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus—are key targets for focal spasticity management. Ultrasound guidance enhances procedural precision and safety by delineating nerve trajectories and avoiding vascular or sensory structures. Cryoneurolysis induces reversible axonal disruption, providing symptom relief lasting approximately 5–6 months. Reported outcomes demonstrate reduced hypertonia, improved range of motion, and enhanced gait function. Conclusions Detailed anatomical and sonoanatomical understanding of lower limb nerve branches optimizes nerve-targeted interventions. Ultrasound-guided cryoneurolysis represents a minimally invasive, effective, and durable option for spasticity management, warranting further clinical evaluation within rehabilitation medicine.
Objective To describe the anatomical and sonoanatomical relevance of intramuscular nerve branches of the leg—particularly of the tibial and common peroneal nerves—in guiding ultrasound-assisted cryoneurolysis for the management of spasticity of the leg muscles. Introduction Spasticity is a sensorimotor control disorder from upper motor neuron injury, characterized by intermittent or sustained involuntary muscle contractions. Leg muscle spasticity can lead to pain, stiffness, contractures, and gait abnormalities, reducing mobility and functional independence. Traditional treatment options, including oral medications, botulinum toxin injections, and chemical neurolysis, often provide incomplete or temporary relief. These interventions carry drawbacks such as systemic side effects and repeated procedures. Consequently, there is a growing need for more precise, safer, and longer-lasting management options.
Cryoneurolysis is a minimally invasive, ultrasound-guided intervention that interrupts motor nerve conduction through localized freezing at temperatures between –60°C and –88°C. The rapid temperature drop produces reversible axonal degeneration while preserving the nerve’s connective tissue framework, allowing regeneration over several months. This results in prolonged reductions in hypertonicity, typically lasting 5–6 months. Unlike chemical neurolysis or botulinum toxin, cryoneurolysis offers selective targeting, minimal systemic risk, and no cumulative dose limitation.
However, successful adoption of cryoneurolysis depends on detailed understanding of the relevant intramuscular nerve anatomy and real-time sonoanatomy. This study outlines key anatomical landmarks, ultrasound techniques, and use of e-stimulation to enhance accuracy and reproducibility of this emerging intervention.
Design A comprehensive literature review was performed focusing on the anatomy and sonoanatomy of the tibial and common peroneal nerves, emphasizing their intramuscular motor branches relevant to spasticity of the leg muscles. Published data from ultrasound imaging atlases and clinical experience in spasticity management were synthesized. The review examined optimal probe positioning, approaches for identifying motor branches, and strategies to improve visualization using vascular landmarks. Integration of e-stimulation and diagnostic nerve block (DNB) techniques were explored as adjuncts for confirming target accuracy.
Results Anatomical Overview The tibial nerve originates from the sciatic nerve and provides motor branches to the gastrocnemius, soleus, plantaris, tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles. It continues distally and divides at the ankle into the medial and lateral plantar nerves. The common peroneal nerve descends laterally around the fibular neck, dividing into the deep and superficial branches that supply the tibialis anterior, peroneus longus, and toe extensors. These intramuscular branches serve as potential focal targets for treating spasticity of the leg muscles.
Sonoanatomical Visualization Ultrasound guidance allows direct visualization of many of these branches, particularly to the gastrocnemius and soleus. Using a high-frequency linear transducer placed transversely over the popliteal fossa, the tibial nerve appears as a hyperechoic, honeycomb-like structure superficial to the popliteal vessels. The motor branches to the medial and lateral heads of the gastrocnemius emerge proximally and can be traced as they enter the muscle bellies.
The soleus branch is located deeper to the gastrocnemius and can be identified near the posterior tibial vessels. Tilting the probe slightly medially or laterally improves definition of the fascial interface. For the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, a more distal and medial approach along the deep posterior compartment enhances visualization. At the ankle, the tarsal tunnel serves as a landmark for identifying the distal bifurcation of the tibial nerve into the plantar branches.
Probe Placement and Strategies Optimal probe placement improves the likelihood of identifying motor branches. The proximal posterior leg provides reliable access to the tibial nerve and its early motor branches. Using the popliteal crease as a reference, short-axis scanning allows tracing of branches as they course through the fascial planes between muscle layers. Dynamic scanning along these planes can be used to confirm continuity from the nerve trunk to intramuscular branches.
Motor branches are frequently located near vascular structures. Doppler ultrasound assists in distinguishing arteries and veins within neurovascular bundles and serves as a guide to locate accompanying nerves. Maintaining the probe perpendicular to the nerve minimizes anisotropy and improves image clarity. Switching between short- and long-axis views allows continuous tracking of the nerve path.
E-Stimulation E-stimulation serves as an effective adjunct to ultrasound for confirming motor branch identity. Low-intensity stimulation ( < 1 mA) delivered via an insulated needle or stimulating probe elicits a visible muscle contraction, verifying accurate localization of the motor branch while avoiding unintended activation of adjacent sensory fibers. This approach is especially valuable in individuals with altered anatomy, fibrosis, or severe spastic deformities, where visual differentiation may be more challenging.
The combined use of ultrasound and e-stimulation provides both visual and functional confirmation, improving procedural accuracy and confidence prior to cryoneurolysis.
Safety and Technical Considerations Ultrasound guidance enhances safety by allowing continuous needle visualization and avoidance of critical vascular or sensory structures. Doppler imaging identifies nearby vessels, while real-time imaging ensures precise probe placement and freezing zone monitoring.
Performing a DNB before cryoneurolysis helps predict therapeutic response and guides the selection of target nerves. Additionally, maintaining the freezing zone within intramuscular branches minimizes the risk of sensory loss or unintended weakness in adjacent muscle groups.
Clinical Outcomes Published reports and preliminary clinical experiences demonstrate significant reductions in muscle tone, improved range of motion, and enhanced gait mechanics following cryoneurolysis of leg muscles affected by spasticity. The effects typically last between 5-6 months, with functional improvements reported in walking confidence and mobility. As the nerve regenerates, function gradually returns, allowing re-treatment if necessary.
Conclusions A detailed understanding of the anatomy and sonoanatomy of the tibial and common peroneal nerve branches is essential for performing cryoneurolysis safely and effectively in patients with spasticity of the leg muscles. Ultrasound guidance allows for direct visualization of intramuscular motor branches, particularly to the gastrocnemius and soleus, while the use of vascular landmarks enhances localization of deeper branches. Combining ultrasound with e-stimulation provides a reliable method for confirming target accuracy and minimizing complications. Cryoneurolysis offers a minimally invasive, selective, and reversible intervention that can provide durable symptom relief and improve functional outcomes.
As this field advances, further studies should focus on refining sonoanatomical mapping, standardizing procedural techniques, and validating clinical outcomes in larger populations.
