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Case Report

Clinical Pain 2023; 22(1): 52-56

Published online June 30, 2023 https://doi.org/10.35827/cp.2023.22.1.52

Copyright © Korean Association of Pain Medicine.

Clinical Effect of Selective Neuroablative Technique Using Radiofrequency on Spasticity in a Patient with Stroke

뇌졸중 환자에서 고주파를 이용한 신경절제술의 경직에 대한 임상적 효과

Hyo Jeong Lee1, Yeon-Jae Seong2, Yoon Ghil Park3

이효정1ㆍ성연재2ㆍ박윤길3

1Department of Rehabilitation Medicine, Bundang Jesaeng Hospital, Seongnam, 2Hafis Clinic, 3Department of Rehabilitation Medicine, Gangnam Severance Hospital, Rehabilitation Institute of Neuromuscular Disease, Yonsei University College of Medicine, Seoul, Korea

분당제생병원 재활의학과1, 하피스의원2, 연세대학교 의과대학 재활의학교실, 강남세브란스병원 재활의학과, 희귀난치성 신경근육병 재활연구소3

Correspondence to:박윤길, 서울시 강남구 언주로 211 ㉾ 06273, 연세대학교 의과대학 재활의학교실, 강남 세브란스병원 재활의학과, 희귀난치성 신경근육병 재활연구소
Tel: 02-2019-3493, Fax: 02-3463-7585
E-mail: drtlc@yuhs.ac

Received: January 27, 2023; Revised: April 29, 2023; Accepted: May 8, 2023

Radiofrequency energy, such as that used in neuroablation, has been applied in various medical and surgical fields. However, no consensus exists regarding neuroablation protocols using radiofrequency. This study aimed to report the effect of a radio-frequency neuroablative technique on spastic foot management in a patient with stroke and present its safety and persistence. A 59-year-old man with hemiplegic gait by the intracerebral hemorrhage had radiofrequency ablation of the motor nerve branch supplying the medial gastrocnemius. The patient’s subjective and objective measurements of the spastic limb improved after the intervention. The effect lasted for 3 months. Radiofrequency neuroablative technique may be beneficial for treating spastic gait in patients with stroke. The above technique must be used to verify patients with spasticity, and research should be investigated to determine appropriated parameters.

KeywordsSpasticity, Radiofrequency ablation

Spasticity is a common motor disorder that occurs after a stroke in approximately 30% of patients. This symptom is a component of the upper motor neuron sign and varies considerably with a velocity-dependent increase in tonic stretch reflexes and exaggerated tendon jerks. It limits the rehabilitation success rate; interferes with posture, sleep, and gait; and can be painful. Various management strategies, including physical therapy, oral medications, chemodenervation, and surgical procedures, have been suggested for spasticity [1]. However, oral medications act on the central nervous system, and chemodenervation has the risk of post-injection weakness includingneutralizing antibodies. Surgical procedures, such as surgical neurolysis, selective neurotomies, and rhizotomies, are usually performed in patients with consistent spasticity after non-surgical procedures.

Radiofrequency (RF) energy, which ablates the targeted nerves or tissues through frictional heating, has been used in various medical and surgical fields. The RF neuroablative technique has been used to reduce the gastrocnemius muscle (GCM) in healthy individuals for cosmetic purposes. The procedure preserves the skin except for a small incision, and ankle movement can be compensated by the soleus muscle [2]. RF energy at different frequencies, known as RF neuromodulation, has been reported to have favorable outcomes in the treatment of pain from an innervated structure [3]. RF, as neuroablation, has been intermittently used to treat intractable spasticity after spinal cord injury or cerebral palsy [4], as well as brain injury [5]. However, no consensus exists regarding neuroablation protocols using RF.

This case study aimed to investigate the effect of neuroablative thermocoagulation using percutaneous RF on spastic foot management in a patient with stroke and determine its safety and persistence.

This study was exempted from review by the Institutional Review Board (IRB) of a tertiary hospital (IRB No. 2020-0581-001). This was a prospective study, and a subject with subacute or chronic stroke was recruited by a clinician during the outpatient rehabilitation period after obtaining approval from the IRB. The inclusion criteria were as follows: 1) hemiplegia caused by unilateral stroke, 2) >3 months post-onset, 3) age >19 years, 4) Modified Ashworth Scale (MAS) score in the lower extremity >grade 1+, and 5) ability to express subjective gait discomfort. The exclusion criteria were as follows: 1) peripheral neuropathy or neuromuscular disease, 2) history of fracture or operation of the lower extremity, 3) history of chemical denervation within 3 months, 4) secondary bacterial infections of the dermatome, and 5) uncontrolled bleeding.

A 59-year-old man had a history of intracerebral hemorrhage in the left basal ganglia 15 years prior to presentation and hypertension and paroxysmal supraventricular tachycardia managed with oral medications. The patient had no cognitive impairment, and his body mass index (BMI) was 22.1 kg/cm2. His ankle plantar flexor spasticity was assessed as grade 2 using the MAS, and weakness was assessed using manual muscle examination. He had a history of alcohol injection into the lower extremity to reduce spasticity a few years ago and had been taking oral baclofen 10 mg for 5 years. He typically exhibited right hemiplegic gait, circumduction, hip spiking with compensated trunk lateral flexion, and claw toe when asked to walk outdoors with the UD-flex. No symmetric or rhythmic gait pattern was noted because of uncontrolled muscle hypertonia, although he could walk outdoors with a habituated pattern. Functional evaluation revealed gait disturbance with a score of 44 on the Berg Balance Scale (BBS) and 34 m in the 2-minute walk test (considering safety) (Table 1). The circumference of the calf, including the GCM, was estimated to be 337 mm at the infrapatellar 10 cm to confirm the hypotrophy induced by the neuroablative technique. The study was fully explained to the patient, and informed consent was obtained. Antiplatelet agents were skipped for 2 days before the intervention.

Table 1 Outcomes of the Subject at Baseline and Post-intervention

Outcome measuresRangeValues
Baseline1 Week4 Weeks14 Weeks
Passive range of motion (Rt.)Ankle dorsiflexion with knee extensionAngle0101010
Ankle dorsiflexion with knee flexionAngle20202020
Manual muscle test (Rt.)Knee extensorGoodGoodGoodGood
Ankle dorsiflexorFairFairFairFair
Ankle plantar flexorTracePoor -Poor -Poor -
Calf circumference (Rt./Lt.)Infra-patellar 10 cm (including gastrocnemius)mm337/355335/355320/355328/355
Modified Ashworth Scale (Rt.)GastrocnemiusGrade2221+
2-Minute walk testm34353330
Berg balance scaleScore44444444
Physician global assessment−4∼+4.320

Another experienced rehabilitation physician performing the neuroablative technique inspected the shape and contour of the medial head of the GCM by resisting the action of inducing maximum contraction of the muscle on the day of the procedure. In addition, the motor nerves innervating the medial GCM were examined using high-resolution ultrasonography (Accuvix V10c system, Samsung Medison Co., Seoul, South Korea) with a linear-array probe (5 to 12 MHz) and surface electromyography/stimulation device (Dantec CLAVIS, REF-9015A0012, Denmark). Mapping the surrounding structures, such as the medial sural cutaneous nerve, popliteal vein, and small saphenous vein of the right leg, was necessary before the intervention. The procedure was performed in the prone position to minimize interference from spasticity (Fig. 1-A). An RF probe connected to a 400-kHz electrical surgical unit (ITC-300D, ITC Co., South Korea) was inserted into the skin below the popliteal crease after administration of local anesthesia using 1% lidocaine (Fig. 2). The motor nerve branches that supplied the medial GCM were continuously ablated using conventional radiofrequency (CRF) (Fig. 1-B). A 120-mm- long, 17-gauge custom-designed bipolar RF-insulated needle probe (Dr. Oppel RF generator by Sometech Medical Co., South Korea and Double Impact by Neomedicals Co., South Korea) with a 7-mm-long exposed active tip facilitated precise ablation of nerve branches with minimal injury to adjacent tissues [2,6]. A temperature of greater than 70°C is produced by alternating current of 100 mA. The subject was administered oral antibiotics and nonsteroidal anti-inflammatory drugs for 5 days. No complications or adverse events were observed.

Figure 1.Intervention approaches. (A) Radiofrequency procedure after local anesthesia in the prone position. (B) The anatomy of the posterior aspect showing the nerve with the popliteal fossa. The motor nerve branch to the medial gastrocnemius was ablated with a radiofrequency probe. The sural cutaneous and communicating nerves run subfascially along the midline of the gastrocnemius bellies. Damage to the sensory nerves must be avoided. N: nerve, P: plantaris, G: gastrocnemius.

Figure 2.(A) Radiofrequency probe (black stick) was connected to a 400-kHz electrical surgical unit. (B) The probe was inserted through a small incision below the popliteal crease to motor nerve branch.

The patient was reported to be satisfied with the hypotonic muscle while walking in the first week of the procedure. He reported an overall lighter sensation in his right leg, and the rigidity caused by the hypertonic muscle was reduced. The physician global assessment, a scoring system from −4 to +4 used to measure the overall response to treatment as assessed by the physician, for change as a worsening, no change, or improvement, also showed +3 scores. The score represented an improvement in the patient’s life after the intervention [7]. The passive range of motion (PROM) of ankle dorsiflexion with knee extension improved to 10° at that time, and muscle weakness improved. The 2-minute walk test was estimated to be 35 m with a slightly smoother alternative step during the functional assessment. The MAS grade did not change. His claw toe was reduced during the walking test after 4 weeks. The PROM, manual muscle test (MMT), and MAS results were consistent. He reported that his feet felt heavier while walking after 14 weeks; however, his feet were still better than those before the procedure. The MAS score improved to grade 1+, and the claw toe was reduced. At rest, the inverted ankle improved slightly to a neutral position. The circumference of the calf was 328 mm at the infrapatellar 10 cm, and the PROM, MMT, and BBS were the same. However, the gait speed decreased in the 2-minute walk test (Table 1).

To the best of our knowledge, this is the first report on the effect of an RF neuroablative technique on spastic foot management in a patient with stroke as well as to present its safety and persistence.

The first selective neurotomy for the treatment of spastic deformities of the foot was reported by Stoffel in 1911 and was a surgical procedure involving partial resection of the motor nerve branches innervating the spastic muscles. In the 1990s, the neurosurgical team reintroduced the technique of electrical stimulation. After the extent of nerve sectioning, the sprouting process explains the recovery strength to baseline after 8 to 12 months. Biosignal transmission between the efferent (motor) innervation of extra- and intrafusal muscle fibers and the afferent (sensory) innervation of muscle spindles should be inhibited by selective peripheral neurotomy or neurolysis to decrease spasticity [1]. However, the anti-spastic effects of these procedures vary, and invasive procedures have considerable side effects such as paresthesia and pain.

To date, many studies have investigated the effects of RF on pain, cosmetic management, as well as spasticity [4,5,8]. Two ablation protocols exist: CRF and pulsed radiofrequency (PRF). In CRF application, a 420-kHz high-frequency alternating current of 90∼125 mA generates a temperature of 60°C to 80°C, which results in selective thermocoagulation of nerve fibers. In PRF, the same frequency alternating current at 200 mA produces a temperature below 45°C. Heat is dissipated by thermal conductance into the surrounding area by bursts and quiet phases [9]. However, PRF does not guarantee nonthermal lesions, and appropriate parameters can be determined by considering the relationship between the electric and thermal fields generated by RF [10].

In this study, our patient responded positively to the neuroablative technique of the motor nerve branch without side effects. The application protocol was different from that used in previous studies. In addition, previous studies have focused on deafferentation and targeted the sensory nerve fibers or the muscle itself [2,4,5]. Paresthesia, a common side effect of thermal lesions in CRF, was not believed to have occurred because the electric field was operated differently. The equipment was produced using impedance-dependent thermocouple monitoring [2] and not through a thermosensor on the electrode tip to prevent effective current delivery into the tissues. In addition, physicians must map the precise anatomy and electrical stimulation using US before procedure to avoid damage to the lateral sural nerve and saphenous vein.

The muscle itself with the same CRF parameters, was effective even after 3 months when targeting healthy people according to a previous study; however, a limit to the duration of the effect exists because the state was not tracked afterward [6]. Cryoneurolysis has been reported to be effective among the neuroablation methods even after 1 year in a case report of a patient with SCI. In addition, both CRF and PRF have different mechanisms in previous studies targeting pain; however, nerve regeneration can be explained [8]. Additional RF research on the motor nerves is required.

A previous study revealed that the volume reduction in calves for the same procedure, evaluated using ultrasonography, had an average of 2.5 cm and was consistently maintained after 6 months [2]. This study showed a volume reduction of 1.7 cm at 1 month, which was preserved for three months after the procedure. As his muscle tone was controlled, his ankle plantar flexors and PROM improved at 3 months. Accordingly, he experienced improvement in his symptoms; however, he did not experience much improvement in functioning. The patient with chronic stroke 15 years prior already had hypotrophied muscles, and his gait kinematics and muscle activity responded to dysfunction of the GCM when compared with the pre-procedure pattern. In addition, more elaborate outcomes, such as gait analysis or pedobarography, are needed for comparison before the procedure to identify subtle differences. Increased experience with RF and a better understanding should be investigated to determine optimal parameters.

Surgical treatment is not commonly used for the management of spasticity. However, to date, intraoperative monitoring, technical development, and novel techniques for modulation or ablation of the targeted nerves have been reported [1,6]. This study showed the effect of a neuroablative technique using RF on spasticity in a patient with chronic stroke, as well as its safety and persistence for 3 months. Further studies are required to compare it with conventional treatment during the subacute phase and for long-term follow-up after 3 months to achieve optimal outcomes of percutaneous RF.

No potential conflict of interest relevant to this article was reported.

  1. Thibaut A, Chatelle C, Ziegler E, Bruno M-A, Laureys S, Gosseries O. Spasticity after stroke: physiology, assessment and treatment. Brain Injury 2013;27:1093-105.
    Pubmed CrossRef
  2. Park YJ, Jo YW, Bang SI, Kim HJ, Lim SY, Mun GH, et al. Radiofrequency volume reduction of gastrocnemius muscle hypertrophy for cosmetic purposes. Aesthetic Plast Surg 2007;31:53-61.
    Pubmed CrossRef
  3. Oh TK, Kim NW, Yim J, Lim H, Park B, Kim DH. Effect of Radiofrequency thermocoagulation of thoracic nerve roots in patients with cancer and intractable chest wall pain. Pain Physician 2018;21:E323-9.
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  4. Reynolds RM, Morton RP, Walker ML, Massagli TL, Browd SR. Role of dorsal rhizotomy in spinal cord injury-induced spasticity. J Neurosurg Pediatr 2014;14:266- 70.
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  5. Herz DA, Looman JE, Tiberio A, Ketterling K, Kreitsch RK, Colwill JC, et al. The management of paralytic spasticity. Neurosurgery 1990;26:300-6.
    Pubmed CrossRef
  6. Park D, Seong YJ, Woo H, Yoo B, Shim D, Kim ES, et al. Paralysis of the gastrocnemius medial head differentially affects gait patterns and muscle activity during level and stair ascent locomotion. Gait Posture 2019;72:222-7.
    Pubmed CrossRef
  7. Standardized Assessments for the Management of Children with Motor Disorders. Physician Global Assessment [Internet]. Available from: http://assesschild.com/physician-global-assessment.
  8. Choi EJ, Choi YM, Jang EJ, Kim JY, Kim TK, Kim KH. Neural ablation and regeneration in pain practice. Korean J Pain 2016;29:3-11.
    Pubmed KoreaMed CrossRef
  9. Usmani H, Dureja GP, Andleeb R, Tauheed N, Asif N. Conventional radiofrequency thermocoagulation vs pulsed radiofrequency neuromodulation of ganglion impar in chronic perineal pain of nononcological origin. Pain Med 2018;19:2348-56.
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  10. Cosman ER, Jr., Cosman ER, Sr. Electric and thermal field effects in tissue around radiofrequency electrodes. Pain Med 2005;6:405-24.
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Article

Case Report

Clinical Pain 2023; 22(1): 52-56

Published online June 30, 2023 https://doi.org/10.35827/cp.2023.22.1.52

Copyright © Korean Association of Pain Medicine.

Clinical Effect of Selective Neuroablative Technique Using Radiofrequency on Spasticity in a Patient with Stroke

Hyo Jeong Lee1, Yeon-Jae Seong2, Yoon Ghil Park3

1Department of Rehabilitation Medicine, Bundang Jesaeng Hospital, Seongnam, 2Hafis Clinic, 3Department of Rehabilitation Medicine, Gangnam Severance Hospital, Rehabilitation Institute of Neuromuscular Disease, Yonsei University College of Medicine, Seoul, Korea

Correspondence to:박윤길, 서울시 강남구 언주로 211 ㉾ 06273, 연세대학교 의과대학 재활의학교실, 강남 세브란스병원 재활의학과, 희귀난치성 신경근육병 재활연구소
Tel: 02-2019-3493, Fax: 02-3463-7585
E-mail: drtlc@yuhs.ac

Received: January 27, 2023; Revised: April 29, 2023; Accepted: May 8, 2023

Abstract

Radiofrequency energy, such as that used in neuroablation, has been applied in various medical and surgical fields. However, no consensus exists regarding neuroablation protocols using radiofrequency. This study aimed to report the effect of a radio-frequency neuroablative technique on spastic foot management in a patient with stroke and present its safety and persistence. A 59-year-old man with hemiplegic gait by the intracerebral hemorrhage had radiofrequency ablation of the motor nerve branch supplying the medial gastrocnemius. The patient’s subjective and objective measurements of the spastic limb improved after the intervention. The effect lasted for 3 months. Radiofrequency neuroablative technique may be beneficial for treating spastic gait in patients with stroke. The above technique must be used to verify patients with spasticity, and research should be investigated to determine appropriated parameters.

Keywords: Spasticity, Radiofrequency ablation

INTRODUCTION

Spasticity is a common motor disorder that occurs after a stroke in approximately 30% of patients. This symptom is a component of the upper motor neuron sign and varies considerably with a velocity-dependent increase in tonic stretch reflexes and exaggerated tendon jerks. It limits the rehabilitation success rate; interferes with posture, sleep, and gait; and can be painful. Various management strategies, including physical therapy, oral medications, chemodenervation, and surgical procedures, have been suggested for spasticity [1]. However, oral medications act on the central nervous system, and chemodenervation has the risk of post-injection weakness includingneutralizing antibodies. Surgical procedures, such as surgical neurolysis, selective neurotomies, and rhizotomies, are usually performed in patients with consistent spasticity after non-surgical procedures.

Radiofrequency (RF) energy, which ablates the targeted nerves or tissues through frictional heating, has been used in various medical and surgical fields. The RF neuroablative technique has been used to reduce the gastrocnemius muscle (GCM) in healthy individuals for cosmetic purposes. The procedure preserves the skin except for a small incision, and ankle movement can be compensated by the soleus muscle [2]. RF energy at different frequencies, known as RF neuromodulation, has been reported to have favorable outcomes in the treatment of pain from an innervated structure [3]. RF, as neuroablation, has been intermittently used to treat intractable spasticity after spinal cord injury or cerebral palsy [4], as well as brain injury [5]. However, no consensus exists regarding neuroablation protocols using RF.

This case study aimed to investigate the effect of neuroablative thermocoagulation using percutaneous RF on spastic foot management in a patient with stroke and determine its safety and persistence.

CASE REPORT

This study was exempted from review by the Institutional Review Board (IRB) of a tertiary hospital (IRB No. 2020-0581-001). This was a prospective study, and a subject with subacute or chronic stroke was recruited by a clinician during the outpatient rehabilitation period after obtaining approval from the IRB. The inclusion criteria were as follows: 1) hemiplegia caused by unilateral stroke, 2) >3 months post-onset, 3) age >19 years, 4) Modified Ashworth Scale (MAS) score in the lower extremity >grade 1+, and 5) ability to express subjective gait discomfort. The exclusion criteria were as follows: 1) peripheral neuropathy or neuromuscular disease, 2) history of fracture or operation of the lower extremity, 3) history of chemical denervation within 3 months, 4) secondary bacterial infections of the dermatome, and 5) uncontrolled bleeding.

A 59-year-old man had a history of intracerebral hemorrhage in the left basal ganglia 15 years prior to presentation and hypertension and paroxysmal supraventricular tachycardia managed with oral medications. The patient had no cognitive impairment, and his body mass index (BMI) was 22.1 kg/cm2. His ankle plantar flexor spasticity was assessed as grade 2 using the MAS, and weakness was assessed using manual muscle examination. He had a history of alcohol injection into the lower extremity to reduce spasticity a few years ago and had been taking oral baclofen 10 mg for 5 years. He typically exhibited right hemiplegic gait, circumduction, hip spiking with compensated trunk lateral flexion, and claw toe when asked to walk outdoors with the UD-flex. No symmetric or rhythmic gait pattern was noted because of uncontrolled muscle hypertonia, although he could walk outdoors with a habituated pattern. Functional evaluation revealed gait disturbance with a score of 44 on the Berg Balance Scale (BBS) and 34 m in the 2-minute walk test (considering safety) (Table 1). The circumference of the calf, including the GCM, was estimated to be 337 mm at the infrapatellar 10 cm to confirm the hypotrophy induced by the neuroablative technique. The study was fully explained to the patient, and informed consent was obtained. Antiplatelet agents were skipped for 2 days before the intervention.

Table 1 . Outcomes of the Subject at Baseline and Post-intervention.

Outcome measuresRangeValues
Baseline1 Week4 Weeks14 Weeks
Passive range of motion (Rt.)Ankle dorsiflexion with knee extensionAngle0101010
Ankle dorsiflexion with knee flexionAngle20202020
Manual muscle test (Rt.)Knee extensorGoodGoodGoodGood
Ankle dorsiflexorFairFairFairFair
Ankle plantar flexorTracePoor -Poor -Poor -
Calf circumference (Rt./Lt.)Infra-patellar 10 cm (including gastrocnemius)mm337/355335/355320/355328/355
Modified Ashworth Scale (Rt.)GastrocnemiusGrade2221+
2-Minute walk testm34353330
Berg balance scaleScore44444444
Physician global assessment−4∼+4.320


Another experienced rehabilitation physician performing the neuroablative technique inspected the shape and contour of the medial head of the GCM by resisting the action of inducing maximum contraction of the muscle on the day of the procedure. In addition, the motor nerves innervating the medial GCM were examined using high-resolution ultrasonography (Accuvix V10c system, Samsung Medison Co., Seoul, South Korea) with a linear-array probe (5 to 12 MHz) and surface electromyography/stimulation device (Dantec CLAVIS, REF-9015A0012, Denmark). Mapping the surrounding structures, such as the medial sural cutaneous nerve, popliteal vein, and small saphenous vein of the right leg, was necessary before the intervention. The procedure was performed in the prone position to minimize interference from spasticity (Fig. 1-A). An RF probe connected to a 400-kHz electrical surgical unit (ITC-300D, ITC Co., South Korea) was inserted into the skin below the popliteal crease after administration of local anesthesia using 1% lidocaine (Fig. 2). The motor nerve branches that supplied the medial GCM were continuously ablated using conventional radiofrequency (CRF) (Fig. 1-B). A 120-mm- long, 17-gauge custom-designed bipolar RF-insulated needle probe (Dr. Oppel RF generator by Sometech Medical Co., South Korea and Double Impact by Neomedicals Co., South Korea) with a 7-mm-long exposed active tip facilitated precise ablation of nerve branches with minimal injury to adjacent tissues [2,6]. A temperature of greater than 70°C is produced by alternating current of 100 mA. The subject was administered oral antibiotics and nonsteroidal anti-inflammatory drugs for 5 days. No complications or adverse events were observed.

Figure 1. Intervention approaches. (A) Radiofrequency procedure after local anesthesia in the prone position. (B) The anatomy of the posterior aspect showing the nerve with the popliteal fossa. The motor nerve branch to the medial gastrocnemius was ablated with a radiofrequency probe. The sural cutaneous and communicating nerves run subfascially along the midline of the gastrocnemius bellies. Damage to the sensory nerves must be avoided. N: nerve, P: plantaris, G: gastrocnemius.

Figure 2. (A) Radiofrequency probe (black stick) was connected to a 400-kHz electrical surgical unit. (B) The probe was inserted through a small incision below the popliteal crease to motor nerve branch.

The patient was reported to be satisfied with the hypotonic muscle while walking in the first week of the procedure. He reported an overall lighter sensation in his right leg, and the rigidity caused by the hypertonic muscle was reduced. The physician global assessment, a scoring system from −4 to +4 used to measure the overall response to treatment as assessed by the physician, for change as a worsening, no change, or improvement, also showed +3 scores. The score represented an improvement in the patient’s life after the intervention [7]. The passive range of motion (PROM) of ankle dorsiflexion with knee extension improved to 10° at that time, and muscle weakness improved. The 2-minute walk test was estimated to be 35 m with a slightly smoother alternative step during the functional assessment. The MAS grade did not change. His claw toe was reduced during the walking test after 4 weeks. The PROM, manual muscle test (MMT), and MAS results were consistent. He reported that his feet felt heavier while walking after 14 weeks; however, his feet were still better than those before the procedure. The MAS score improved to grade 1+, and the claw toe was reduced. At rest, the inverted ankle improved slightly to a neutral position. The circumference of the calf was 328 mm at the infrapatellar 10 cm, and the PROM, MMT, and BBS were the same. However, the gait speed decreased in the 2-minute walk test (Table 1).

DISCUSSION

To the best of our knowledge, this is the first report on the effect of an RF neuroablative technique on spastic foot management in a patient with stroke as well as to present its safety and persistence.

The first selective neurotomy for the treatment of spastic deformities of the foot was reported by Stoffel in 1911 and was a surgical procedure involving partial resection of the motor nerve branches innervating the spastic muscles. In the 1990s, the neurosurgical team reintroduced the technique of electrical stimulation. After the extent of nerve sectioning, the sprouting process explains the recovery strength to baseline after 8 to 12 months. Biosignal transmission between the efferent (motor) innervation of extra- and intrafusal muscle fibers and the afferent (sensory) innervation of muscle spindles should be inhibited by selective peripheral neurotomy or neurolysis to decrease spasticity [1]. However, the anti-spastic effects of these procedures vary, and invasive procedures have considerable side effects such as paresthesia and pain.

To date, many studies have investigated the effects of RF on pain, cosmetic management, as well as spasticity [4,5,8]. Two ablation protocols exist: CRF and pulsed radiofrequency (PRF). In CRF application, a 420-kHz high-frequency alternating current of 90∼125 mA generates a temperature of 60°C to 80°C, which results in selective thermocoagulation of nerve fibers. In PRF, the same frequency alternating current at 200 mA produces a temperature below 45°C. Heat is dissipated by thermal conductance into the surrounding area by bursts and quiet phases [9]. However, PRF does not guarantee nonthermal lesions, and appropriate parameters can be determined by considering the relationship between the electric and thermal fields generated by RF [10].

In this study, our patient responded positively to the neuroablative technique of the motor nerve branch without side effects. The application protocol was different from that used in previous studies. In addition, previous studies have focused on deafferentation and targeted the sensory nerve fibers or the muscle itself [2,4,5]. Paresthesia, a common side effect of thermal lesions in CRF, was not believed to have occurred because the electric field was operated differently. The equipment was produced using impedance-dependent thermocouple monitoring [2] and not through a thermosensor on the electrode tip to prevent effective current delivery into the tissues. In addition, physicians must map the precise anatomy and electrical stimulation using US before procedure to avoid damage to the lateral sural nerve and saphenous vein.

The muscle itself with the same CRF parameters, was effective even after 3 months when targeting healthy people according to a previous study; however, a limit to the duration of the effect exists because the state was not tracked afterward [6]. Cryoneurolysis has been reported to be effective among the neuroablation methods even after 1 year in a case report of a patient with SCI. In addition, both CRF and PRF have different mechanisms in previous studies targeting pain; however, nerve regeneration can be explained [8]. Additional RF research on the motor nerves is required.

A previous study revealed that the volume reduction in calves for the same procedure, evaluated using ultrasonography, had an average of 2.5 cm and was consistently maintained after 6 months [2]. This study showed a volume reduction of 1.7 cm at 1 month, which was preserved for three months after the procedure. As his muscle tone was controlled, his ankle plantar flexors and PROM improved at 3 months. Accordingly, he experienced improvement in his symptoms; however, he did not experience much improvement in functioning. The patient with chronic stroke 15 years prior already had hypotrophied muscles, and his gait kinematics and muscle activity responded to dysfunction of the GCM when compared with the pre-procedure pattern. In addition, more elaborate outcomes, such as gait analysis or pedobarography, are needed for comparison before the procedure to identify subtle differences. Increased experience with RF and a better understanding should be investigated to determine optimal parameters.

Surgical treatment is not commonly used for the management of spasticity. However, to date, intraoperative monitoring, technical development, and novel techniques for modulation or ablation of the targeted nerves have been reported [1,6]. This study showed the effect of a neuroablative technique using RF on spasticity in a patient with chronic stroke, as well as its safety and persistence for 3 months. Further studies are required to compare it with conventional treatment during the subacute phase and for long-term follow-up after 3 months to achieve optimal outcomes of percutaneous RF.

CONFLICTS OF INTEREST

No potential conflict of interest relevant to this article was reported.

FUNDING

This study was supported by the Hafis Clinic.

Fig 1.

Figure 1.Intervention approaches. (A) Radiofrequency procedure after local anesthesia in the prone position. (B) The anatomy of the posterior aspect showing the nerve with the popliteal fossa. The motor nerve branch to the medial gastrocnemius was ablated with a radiofrequency probe. The sural cutaneous and communicating nerves run subfascially along the midline of the gastrocnemius bellies. Damage to the sensory nerves must be avoided. N: nerve, P: plantaris, G: gastrocnemius.
Clinical Pain 2023; 22: 52-56https://doi.org/10.35827/cp.2023.22.1.52

Fig 2.

Figure 2.(A) Radiofrequency probe (black stick) was connected to a 400-kHz electrical surgical unit. (B) The probe was inserted through a small incision below the popliteal crease to motor nerve branch.
Clinical Pain 2023; 22: 52-56https://doi.org/10.35827/cp.2023.22.1.52

Table 1 Outcomes of the Subject at Baseline and Post-intervention

Outcome measuresRangeValues
Baseline1 Week4 Weeks14 Weeks
Passive range of motion (Rt.)Ankle dorsiflexion with knee extensionAngle0101010
Ankle dorsiflexion with knee flexionAngle20202020
Manual muscle test (Rt.)Knee extensorGoodGoodGoodGood
Ankle dorsiflexorFairFairFairFair
Ankle plantar flexorTracePoor -Poor -Poor -
Calf circumference (Rt./Lt.)Infra-patellar 10 cm (including gastrocnemius)mm337/355335/355320/355328/355
Modified Ashworth Scale (Rt.)GastrocnemiusGrade2221+
2-Minute walk testm34353330
Berg balance scaleScore44444444
Physician global assessment−4∼+4.320

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Korean Association of Pain Medicine

Vol.22 No.2
December 2023

eISSN: 2765-5156

Frequency: Semi Annual

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