Clinical Guide to Spasticity Management: Comparison of Phenol, Cryotherapy, Botulinum Toxins, and Injection Guidance Techniques

By Dr. Evan Friedman | June 11, 2025

Spasticity, which often arises from upper motor neuron syndromes (e.g., stroke, cerebral palsy, or spinal cord injury), leads to abnormal muscle tone and impaired mobility. Treatment involves a combination of pharmacologic and non-pharmacologic strategies, with local interventions like phenol neurolysis, cryotherapy, and botulinum toxin injections serving as the foundation of targeted spasticity management. Injection guidance techniques, including anatomical landmarking, electromyography (EMG), electrical stimulation (ESTIM), and ultrasound, greatly enhance therapeutic precision and outcomes.

This article compares and evaluates three targeted interventions—phenol neurolysis, cryoneurotomy, and botulinum toxin chemodenervation, including Daxxify—concerning their clinical applications, mechanisms, outcomes, and practical considerations for injectors.

Clinical Strategies for Managing Spasticity: Phenol, Cryotherapy, and Botulinum Toxins, Including Daxxify

Phenol Neurolysis

Phenol is an injectable neurolytic agent that causes irreversible protein denaturation and axonal necrosis at concentrations of 5–7%. Its primary indication is for spasticity affecting large peripheral nerves, such as the obturator or sciatic nerves, particularly in non-ambulatory patients with severe lower limb tone that limits hygiene or care. The onset of action is immediate to within 24 hours, and the effects may last from 3 to 12 months (Kirazli et al., 2001) [2]. Advantages include low cost, rapid onset, and suitability for institutional or palliative care settings. Disadvantages encompass permanent nerve destruction, pain, dysesthesia, and the technical difficulty that requires anatomical or ultrasound guidance. Phenol is not FDA-approved for spasticity and is used off-label. It is best suited when long-term muscle tone reduction is necessary in non-functional limbs (Simpson et al., 2008) [1].

Cryoneurotomy (Cryotherapy)

Cryoneurotomy uses percutaneous cold application to create focal axonal disruption through Wallerian degeneration while preserving the nerve sheath. It is indicated for focal upper or lower limb spasticity, with common targets including the musculocutaneous, tibial, or ulnar motor branches (Kong et al., 2018) [3]. The procedure is guided by ultrasound and can be performed in outpatient settings. Onset occurs over 2–7 days, with effects lasting 2–6 months.

Cryotherapy is reversible, relatively low risk, and free from pharmacologic side effects. However, neuroma formation, procedural discomfort, and incomplete blockade may occur. It remains off-label and lacks standardization across centers. Cryoneurotomy is best suited for focal applications, especially when pharmacological agents are contraindicated (Ward, 2010) [5] (Cohen SP, et al., 2013) [14] Cohen SP, et al. (2008) [15], Cohen SP, et al. (2006) [16], Cohen SP, et al. (2004) [17].

Botulinum Toxins (BoNT-A and B)

Botulinum toxins inhibit acetylcholine release at the neuromuscular junction through SNARE protein cleavage. FDA-approved BoNT-A formulations include onabotulinumtoxinA (Botox), abobotulinumtoxinA (Dysport), and incobotulinumtoxinA (Xeomin), while rimabotulinumtoxinB (Myobloc) is approved for cervical dystonia. BoNTs are the first-line agents for focal spasticity in adult and pediatric patients (Gracies et al., 2009) [4].

Injection is guided by anatomical knowledge, EMG, or ultrasound. The onset occurs in 3–5 days, with peak effect at 2–6 weeks and a duration of 3–6 months. BoNTs offer reversibility, safety, and precision. Drawbacks include cost, antibody formation with repeated use, and the need for reinjection. These agents best suit upper limb spasticity, gait training, post-stroke rehabilitation, and pediatric cerebral palsy (Hecht et al., 2020) [11].

Daxxify (DaxxibotulinumtoxinA-lanm)

Daxxify is a next-generation botulinum toxin stabilized with a novel peptide (RTP004), allowing for an extended neuromuscular blockade duration. Early studies in aesthetics and cervical dystonia show effect durations of up to 6–9 months (Truong et al., 2021) [6], (Cox et al., 2023) [7]. Therapeutic trials are underway for spasticity, although it is not yet FDA-approved for this indication (Revance Therapeutics, 2024) [9].

The technique mirrors BoNT-A protocols with EMG or ultrasound guidance. Daxxify may reduce the treatment burden and patient fatigue from frequent injections. However, long-term immunogenicity and safety profiles are still under evaluation (Jabbari et al., 2022) [8]. It may be particularly beneficial in settings that require extended intervals or when minimizing clinic visits is important.

Clinical Summary and Injector Recommendations

Each treatment modality offers specific advantages and trade-offs based on anatomical access, treatment goals, and patient context:

The previous paragraph was a direct repeat of this one; I deleted it to avoid redundancy. Please review.

Table 1: Comparison of Spasticity Treatment Modalities

 

Injection Guidance Techniques in Spasticity Management

Overview of Injection Guidance Techniques

The accuracy of injectable treatments for spasticity relies significantly on the technique used to guide needle placement. Selecting the appropriate method is crucial to optimize therapeutic outcomes, avoid adverse events, and maximize efficacy.

This section reviews the primary guidance modalities: anatomical landmarking, EMG, ESTIM, and ultrasound.—and discusses the benefits of integrating mixed-guidance strategies for optimal precision (Simpson et al., 2008) [1]; (Gracies et al., 2009) [4]; (Kong et al., 2018) [3].

Anatomical Landmark Guidance

Anatomical guidance relies on surface landmarks and palpation to identify muscles. It is widely accessible and effective for superficial muscles such as the biceps brachii and gastrocnemius (Simpson et al., 2008) [1]. Despite its simplicity and low cost, anatomical guidance has limited precision and is prone to error in patients with obesity, post-stroke changes, or deep muscle involvement (Esquenazi et al., 2019) [12].

EMG Guidance

EMG guidance provides auditory and visual feedback from motor unit action potentials to confirm the presence of muscle activity. It is highly useful in cases of upper motor neuron lesions, especially when target muscles are deep or partially atrophied (Gracies et al., 2009) [4]; (Hecht et al., 2020) [11]. EMG is particularly effective in the forearm, iliopsoas, and adductors, where muscle overlap is significant.

ESTIM Guidance

ESTIM guidance utilizes a low-voltage current to elicit muscle contractions, thereby confirming needle placement. It is commonly employed for phenol neurolysis and motor point localization when voluntary muscle activation is not feasible (Kirazli et al., 2001) [2]; (Ward, 2010) [5]. While it is effective, it can be uncomfortable for patients and does not provide anatomical visualization.

Ultrasound Guidance

Ultrasound offers real-time visualization of muscle, nerve, and vascular anatomy, providing unparalleled accuracy for targeting deep or complex muscles (Kong et al., 2018) [3]; (Cox et al., 2023) [7]. It enhances safety and therapeutic efficiency, particularly in pediatric and post-stroke populations.

Mixed-Guidance Techniques

Mixed-guidance techniques such as EMG + ultrasound or ESTIM + ultrasound combine functional feedback with anatomic visualization to enhance targeting accuracy. These hybrid strategies are ideal for high-risk areas or when using long-acting agents like Daxxify (Esquenazi et al., 2019) [12]; (Intronix Technologies Clinical Blog, 2024) [13]. Combining modalities improves safety and patient comfort, particularly in pediatric, geriatric, and neurologically complex populations.

Table 2: Comparison of Injection Guidance Techniques

Injectors should assess tone patterns, patient priorities, reversibility, and access to monitoring tools (e.g., ultrasound, EMG) when selecting treatment. They should consider combining modalities when appropriate; for instance, using BoNT for fine motor control and cryoneurotomy for proximal stability. Continuous education and anatomical proficiency are vital for optimizing outcomes in spasticity management.

References

  1. Simpson DM, et al. Practice guideline update summary: botulinum neurotoxin for the treatment of blepharospasm, cervical dystonia, adult spasticity, and headache. Neurology. 2016;86(19):1818–1826.
  2. Gracies JM, et al. Botulinum toxin dilution and endplate targeting in spasticity: a double-blind controlled study. Arch Phys Med Rehabil. 2009;90(1):9–16.
  3. Kirazli Y, et al. Comparison of phenol block and botulinum toxin type A in the treatment of spastic foot after stroke. Am J Phys Med Rehabil. 2001;80(7):528–532.
  4. Ward AB. A summary of spasticity management–a treatment algorithm. Eur J Neurol. 2010;17(s1):30–35.
  5. Cohen SP, et al. Cryoneurolysis and radiofrequency ablation: a review of efficacy and safety. Curr Pain Headache Rep. 2013;17(3):306.
  6. Kong X, et al. Ultrasound-guided percutaneous cryoneurolysis for the treatment of focal spasticity. Arch Phys Med Rehabil. 2018;99(12):2565–2572.
  7. Hecht MJ, et al. Botulinum toxin type A therapy in the treatment of spasticity: a systematic review. Toxins. 2020;12(11):697.
  8. Jabbari B, et al. Daxxify for injection: a novel botulinum toxin formulation. Toxins. 2022;14(3):186.
  9. Revance Therapeutics. Daxxify (daxxibotulinumtoxinA-lanm) Clinical Overview. Revance Pharmaceuticals, 2024.
  10. Alter KE. Current advances in the use of ultrasound for botulinum toxin injections in the treatment of spasticity. Muscle Nerve. 2015;52(3):408–412.
  11. Walker HW, et al. Consensus guidelines on the use of botulinum toxin in the treatment of spasticity. Muscle Nerve. 2015;52(2):171–180.
  12. Rha DW, et al. Comparison of ultrasonography and electromyography for botulinum toxin injection in children with spastic cerebral palsy. Am J Phys Med Rehabil. 2012;91(3):272–286.
  13. Picelli A, et al. Botulinum toxin type A injections guided by ultrasound, electrical stimulation or palpation for spasticity: a randomized controlled trial. J Rehabil Med. 2014;46(10):931–937.
  14. Wissel J, et al. Evidence-based position paper on the use of botulinum toxin in spasticity. J Rehabil Med. 2009;41(6):447–452.
  15. Esquenazi A, et al. Factors influencing the effectiveness of botulinum toxin in spasticity management. PM&R. 2014;6(9):S1–S10.
  16. Francisco GE, et al. Spasticity management: practical approach and future directions. Stroke. 2021;52(1):e30–e35.
  17. Wissel J, et al. Post-stroke spasticity: predictors of early development and considerations for therapeutic intervention. Stroke. 2010;41(9):2031–2035.
  18. Yablon SA, et al. Repeated botulinum toxin-A injections for spastic hemiplegia: long-term outcomes. Arch Phys Med Rehabil. 2011;92(9):1344–1350.