Motor Branching Pattern of the Radial Nerve for Hyperselective Neurectomy: From Anatomy to Clinical Translation.

PURPOSE: Predominant or isolated spasticity of the triceps following upper motor neuron injury is rare and often unmasked once the spastic elbow flexors are addressed. The purpose of this study was to delineate the motor branching pattern of the radial nerve to determine the feasibility of hyperselective neurectomies (HSN) for triceps spasticity. METHODS: Dissections of the motor branch to each triceps head were performed on 11 upper-extremity specimens. The numbers of trunks, branching patterns, and muscle entry points were recorded in reference to the acromion to interepicondylar line. Based on anatomic studies, 10 patients underwent a combined fractional lengthening and HSN procedure for triceps spasticity. Patient demographics, time from diagnosis, and complications were recorded. Preoperative and postoperative Modified Ashworth Scale (MAS) and total active elbow arc of motion were compared. RESULTS: The first branch from the radial nerve was consistently a single trunk to the long triceps head. There were many variations in the branching pattern and number of trunks to the lateral and medial heads of the triceps with motor entry points between 31% and 95% of the acromion to interepicondylar line distance. Ten patients (six men and four women; mean age: 48.5 years) underwent the combined procedure. Mean total active elbow arc of motion improved from 78° before surgery to 111° after surgery, with a 17.5° increase in active elbow flexion. Compared with a mean preoperative triceps MAS of 2.75, nine patients had triceps MAS of 0 at a mean of 10.2 months of follow-up. There was no loss of functional elbow extension and no directly related complications. CONCLUSIONS: Given the variable motor entry points, HSN to each triceps head would require extensive dissection. Therefore, a combined approach consisting of fractional lengthening of the long head and lateral head with HSN of the triceps medial head is recommended to address triceps spasticity. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Anatomical study of the motor branches of the tibial nerve and incision design for hyperselective neurectomy.

PURPOSE: Selective tibial neurotomy (STN) is a surgical procedure for treating spastic equinovarus foot. Hyperselective neurectomy (HSN) of tibial nerve is a modified STN procedure, which was rarely discussed. This study aimed to describe the branching patterns of the tibial nerve and propose an optimal surgical incision of HSN for treatment of spastic equinovarus foot. METHODS: Sixteen lower limbs were dissected to determine the various branching patterns of the tibial nerve and categorized according to these branching patterns. The mean distances from the nerve entry points to the tip of femur's medial epicondyle were measured, as well as their percentage to the overall length of the leg. The surgical incision was designed according to the range of these nerve entry points. RESULTS: The tibial nerve sent out proximal and distal motor branches based on their position relative to the soleus muscle's tendinous arch. For proximal motor branches, the branches innervating the medial gastrocnemius, lateral gastrocnemius and proximal soleus were categorized into types I (9/16), II (5/16) and III (2/16). Measurements from the medial epicondyle to the nerve entry points into the medial gastrocnemius, lateral gastrocnemius and proximal soleus ranged from 14 to 33 mm (4-9% of leg length), 22-45 mm (6-12%) and 35-81 mm (10-22%), respectively. Distal motor branches including the distal soleus, posterior tibialis, flexor digitorum longus and flexor hallucis longus, were classified as types A (8/14), B (4/14) and C (2/14), with the distances from their respective terminal points to the medial epicondyle were 67-137 mm (19-39%), 74-125 mm (20-35%), 116-243 mm (33-69%) and 125-272 mm (35-77%). CONCLUSIONS: The motor branches of tibial nerve were classified into two groups and each subdivided into three types. Detailed location parameters may serve as an anatomical basis for designing incision of HSN.

Nerve-Targeted Surgical Treatments for Spasticity: A Narrative Review.

Spasticity is a potentially debilitating symptom of various acquired and congenital neurologic pathologies that, without adequate treatment, may lead to long-term disability, compromise functional independence, and negatively impact mental health. Several conservative as well as non-nerve targeted surgical strategies have been developed for the treatment of spasticity, but these may be associated with significant drawbacks, such as adverse side effects to medication, device dependence on intrathecal baclofen pumps, and inadequate relief with tendon-based procedures. In these circumstances, patients may benefit from nerve-targeted surgical interventions such as (i) selective dorsal rhizotomy, (ii) hyperselective neurectomy, and (iii) nerve transfer. When selecting the appropriate surgical approach, preoperative patient characteristics, as well as the risks and benefits of nerve-targeted surgical intervention, must be carefully evaluated. Here, we review the current evidence on the efficacy of these nerve-targeted surgical approaches for treating spasticity across various congenital and acquired neurologic pathologies.

Trends and insights review. Nerve procedures in the management of upper limb spasticity.

This article reviews the recent advances or nerve-oriented surgical procedures in the treatment of the spastic upper limb. The idea to intervene on the nerve is not recent, but new trends have developed in nerve surgery over the past few years, stimulating experiments and research. Specific surgical procedures involving the nerves have been described at different levels from proximal to distal: at the cervical spinal cord and the dorsal root entry zone (rhizotomy), at the level of the roots (contralateral C7 transfer) or in the peripheral nerve, within the motor trunk (selective neurectomy) or as its branches penetrate the muscles (hyperselective neurectomy). All of these neurosurgical procedures are only effective on spasticity but do not address the other deformities, such as contractures and motor deficit. Additional procedures may have to be planned in conjunction with nerve procedures to optimize outcomes.

Hyperselective neurectomy of thoracodorsal nerve for treatment of the shoulder spasticity: anatomical study and preliminary clinical results.

BACKGROUND: Hyperselective neurectomy is a reliable treatment for spasticity. This research was designed to quantify the surgical parameters of hyperselective neurectomy of thoracodorsal nerve for shoulder spasticity through anatomical studies, as well as to retrospectively assess patients who underwent this procedure to provide an objective basis for clinical practice. METHODS: On nine embalmed adult cadavers (18 shoulders), we dissected and observed the branching patterns of thoracodorsal nerve, counted the number of nerve branches, measured the distribution of branch origin point, and determined the length of the surgical incision. Next, we selected five patients who underwent this procedure for shoulder spasticity and retrospectively evaluated (ethic committee: 2022-37) their shoulder function with active/passive range of motion (AROM/PROM) and modified Ashworth scale (MAS). RESULTS: The anatomical study revealed that the main trunk of thoracodorsal nerve sends out one to three medial branches, with the pattern of only one medial branch being the most common (61.1%); there were significant variations in the branch numbers and nerve distributions; the location of thoracodorsal nerve branches' entry points into the muscle varied from 27.2 to 67.8% of the length of the arm. Clinical follow-up data showed significant improvement in shoulder mobility in all patients. AROM of shoulder abduction increased by 39.4° and PROM increased by 64.2° (P < 0.05). AROM and PROM of shoulder flexion increased by 36.6° and 54.4°, respectively (P < 0.05). In addition, the MAS of shoulder abduction (1.8) and flexion (1.2) was both significantly reduced in all patients (P < 0.05). CONCLUSION: Hyperselective neurectomy of thoracodorsal nerve is effective and stable in the treatment of shoulder spasticity. Intraoperative attention is required to the numbers of the medial branch of thoracodorsal nerve. We recommend an incision in the mid-axillary line that extends from 25 to 70% of the arm length to fully expose each branch.

Hyperselective neurectomy for the treatment of upper limb spasticity in adults and children: a prospective study.

Hyperselective neurectomy (HSN) procedures in the spastic upper limb aim to reduce tone by excising some branches of the involved peripheral motor nerves, at the point of entry of each motor ramus into the target muscle. In this prospective study, 42 patients with upper limb spasticity were treated by HSN for the muscles of elbow flexion, forearm pronation and wrist flexion and evaluated for their short-term results (average 6 months) and long-term outcomes (average 31 months). Results at both time points showed an effective reduction of the spastic tone, with no decrease of muscle strength in the operated spastic muscles. Comparison of results between the two time points showed durability of the improvement, which remained statistically significant despite a slight relapse in spasticity. The results of HSN compare favourably with the other techniques of partial neurectomy; however, the technique requires a detailed knowledge of upper limb motor anatomy.Level of evidence: II.

Hyperselective neurectomy in the treatment of elbow and wrist spasticity: an anatomical study and incision design.

OBJECTIVE: Hyperselective neurectomy is used to treat spastic arm paralysis. The aim of the study was to analyze the nerve branching patterns of elbow and wrist flexors/pronator to inform hyperselective neurectomy approached. METHODS: Eighteen upper extremities of fresh cadaver specimen were dissected. The number of motor branches from the musculocutaneous nerve to biceps brachii and brachialis, median nerve to pronator teres, flexor carpi radialis and ulnar nerve to flexor carpi ulnaris were counted. The origin site of each primary motor branch was documented. RESULTS: Either biceps or brachialis was innervated by one or two primary motor branches. Pronator teres was innervated by one to three motor trunks and the pattern for flexor carpi radialis was a common trunk with other branches. The origin of the biceps and brachialis nerve trunk was located approximately 30% to 60% of the length of the arm. The median nerve branched to pronator teres and flexor carpi radialis at the region about 34mm (SD 18.8mm) above and 50mm (SD 14.9mm) below the medial epicondyle. Flexor carpi ulnaris was innervated by one to three motor trunks and the mean distance from the medial epicondyle to the origin of flexor carpi ulnaris nerve on ulnar nerve was 18.7 mm (SD 6.5mm). CONCLUSION: Primary motor branches to elbow flexors, wrist flexors and pronators were various, while the regions of their origins were relatively settled. It was recommended the incisions be designed according to the location of the primary motor trunks.

Selective Neurectomy for the Spastic Upper Extremity.

Surgery is one element of the rehabilitative care of the spastic upper limb. Different surgical techniques have been advocated to address each of the common deformities and underlying causes, including muscle spasticity, joint contracture, and paralysis. Partial neurectomy of motor nerves has been shown to reduce spasticity in the target muscles. It is effective only for the spastic component of the deformity, which underscores the importance of a preliminary thorough clinical examination. Hyperselective neurectomy, which involves performing a partial division of each motor ramus at its entry point into the target muscle, results in improved selectivity, reliable partial muscle denervation, and durable results.

Spasticity and hyperselective neurectomy in the upper limb.

Spasticity is a complex pathology, both in terms of assessment and treatment. This article focuses on the clinical examination (objective, capacity, performance and function), which is key for choosing a treatment and can be helped by botulinum toxin injections. The treatment involves physical therapy, occupational therapy, medications and surgery. Neurectomy has been used in the upper limb since 1912 and is one of the therapeutic options for spasticity. This treatment is usually reserved for nonfunctional hands. Cadaver studies have helped us better understand nerve anatomy and improve the hyperselective neurectomy (HSN) technique. This article describes the history of neurectomy, how anatomical dissections apply to surgery, the HSN technique in the musculocutaneous nerve, median nerve and ulnar nerve and results of preliminary prospective studies. Spasticity, mobility, performance and function were evaluated a few months after HSN and about 12 months later to assess the permanence of the results in children and adult spastic patients. No matter the nerve or function targeted (elbow extension, wrist extension, or supination), spasticity was reduced with improvements in the functional House score and appeared stable at the last follow-up. HSN seems to be a good, reliable therapeutic option for spasticity, including functional hands.