Outcome of selective motor fasciculotomy in the treatment of upper limb spasticity

Abstract

Objective:

The objective was to assess the outcome of selective motor fasciculotomy in relieving upper limb harmful resistant spasticity and thereby to improve motor functions in persons with cerebral palsy.

Materials and Methods:

Twenty people having cerebral palsy (12 females and 8 males) with age ranging from 5 to 35 (mean 12.85) years with upper limb resistant spasticity due to spastic hemiplegia (n=7), triplegia (n=6), and quadriplegia (n=7) were assessed using Modified Ashworth Scale, Selective Voluntary Control Grade, Wee FIM Scale and hand function evaluation. Selective motor fasciculotomy was performed on the musculocutaneous nerve (n=13) for elbow flexors spasticity, median nerve (n=24) for pronators and radial wrist flexors spasticity and ulnar nerve (n=3) for ulnar wrist flexors spasticity. Pre- and post-op therapeutic exercises were performed.

Results:

Statistical analysis using the Wilcoxon Signed Ranks test showed significant reduction in spasticity and improvement in selective voluntary control, hand functions (grasp to hold a 2 inch rod), and Wee FIM (self-care domain in particular). There was no recurrence in spasticity and complications following surgery.

Conclusions:

The selective motor fasciculotomy of musculocutaneous, median, and ulnar nerves significantly reduces spasticity in the affected muscle groups and thereby improves the self-care (motor) functions in selected people with cerebral palsy who have harmful resistant spasticity without any organic shortening of the muscles. The procedure is safe and the spasticity does not recur.

INTRODUCTION

Upper limb spasticity and dystonia in nonprogressive neurological disorders are at times challenging to treat because these impairments restrict activities of daily living, hamper vocational skills, produce pains and complications; and are cosmetically unacceptable. Treatment modalities like therapeutic exercises, botulinum toxin, etc. may not permanently relieve these impairments.[1–5] Such resistant cases may improve with surgical procedure like selective motor fasciculotomy (SMF), in which the nerve supplying the spastic/dystonic muscles is exposed close to the muscle and the component fascicles are stimulated.[6–14] The fascicles found carrying excessive impulses, are ablated, but not more than three-fourth, thereby permanent relief in harmful spasticity and dystonia is obtained without losing control and balance.

Materials and Methods

Study design

This prospective study included 24 patients who underwent selective motor fasciculotomy (SMF) for the treatment of spasticity in upper limbs due to cerebral palsy (nonprogressive neurological disorder) from January 2008 to December 2009.

Exclusion criteria

1. Poor motor control in upper limbs.

2. Moderate to severe contractures in upper limbs.

3. Severe mental subnormality.

Preoperative evaluation

All the patients having upper limb spasticity due to cerebral palsy were evaluated for muscle spasticity and control by using Modified Ashworth's Scale and Selective Voluntary Control Grading [Tables 1 and 2] respectively.[15–18] The limb functions were evaluated using Wee FIM Scale [Table 3] and by measuring opposition, pinch, and grasp. Each limb function was classified into good, fair, and poor, where good was near normal function, fair was impaired function but still the function was possible and poor when the patient could not attempt the function.

Table 1.

Modified ashworth scale

Table 2.

Selective voluntary control grade

Table 3.

Functional independence measure scale (FIM)

Following development of resistance to nonablative therapies, patients were taken up for SMF. The goals of surgery and further treatment including the need to continue therapeutic exercises were discussed in detail with the parents prior to surgery. They were also explained regarding the possibility of second-stage surgery which included more ablation of the same nerve or the ablation of another nerve of the affected muscle group in cases who have residual spasticity and if that hampers further improvement.

All patients who were planned for SMF were admitted and routine blood investigations were performed. Patients were kept fasting 6 hours prior to surgery. On the day of surgery thorough bath was given and the limbs were wrapped in povidone iodine gauge bandages.

Surgery

Intravenous line was placed in nonoperative limb and antibiotics were given. The patient was positioned supine with arms abducted by 45° and placed over sidearm rest. Single low dose of vecuronium was given during induction of general anesthesia. Reassessment of the contractures was performed. Operative limb was cleaned with povidone iodine scrub and solution, and the body was draped keeping operative limb fully exposed so that the movements of the limb can be observed well during electrostimulation of the nerve. Intradermal infiltration of lignocaine mixed with adrenalin (1 in 200,000) was used to raise a peau-de-orange patch along the line of incision. Care was taken to avoid injecting the drug into the deeper plains so as to prevent infiltration of the underlying nerve, which may otherwise lead to erroneous muscle contraction findings during the stimulation of the nerve.

Musculocutaneous nerve

The skin was incised at a point 2 ± 1 cm distal to the tendinous lateral-most end of the anterior axiliary fold and carried up to 6 ± 4 cm distally. The skin, subcutaneous tissue, superficial and deep fascia were incised along the line of incision and glistening aponeurosis of the biceps brachii was exposed. It was incised longitudinally and the muscle was split along the long axis of its fibers (muscle splitting approach) with the help of artery forceps and right angle retractors. The index finger was also used to split the muscle and palpate the nerve which feels like a cord. The nerve was found underneath the biceps brachii and over the brachialis. The nerve was further dissected along its long axis with the help of peanut size cottonoids. The epineurium was incised along the long axis of the nerve. The branches were dissected till their entry into the muscles.

Median nerve

A horizontal skin crease incision was given in the cubital fossa. Skin, subcutaneous tissue superficial, and deep fascia were incised along the line of incision, and bicipital aponeurosis was exposed. It was incised transversely toward the medial aspect up to the pronator teres muscle leaving the main tendon intact. The nerve was found between the two heads of pronator teres. It was further dissected along its long axis with the help of peanut size cottonoids. The epineurium was incised along the long axis of the nerve. A proximal branch exiting from the main trunk proximal to the transverse elbow line, running medially and entering into the muscle, was split into its component fascicles and a distal branch running along the ventral aspect of the main trunk, which could be easily lifted away from the main trunk, was found disappearing at the distal end of the wound under the muscles of the forearm, and was also dissected into its component fascicles [Figure 1].

Figure 1.

Median nerve exposed in the elbow by transverse skin crease incision. Fascicles supplying Pronator Teres are dissected from the median nerve

The wrist flexor branch(s) exiting medially from the main trunk, distal to the transverse elbow crease, was also dissected into its component fascicles.

Ulnar nerve

The skin was incised longitudinally, one-fourth above and three-fourth below the transverse elbow line, in the groove between the medial epicondyle and olecranon process. The subcutaneous tissue, and superficial and deep fascia were incised along the line of the incision. The ulnar nerve was dissected in between the two heads of flexor carpi ulnaris. The epineurium was incised along the long axis of the nerve. The dissection was performed from the trunk of the nerve along its branches till its ramification as fascicles into the muscle. The branch at the site of its entry into the muscle was found as the ideal site for dissection, as the natural process of separation into fascicles was observed clearly at this site.

Each fascicle was stimulated using bipolar current starting from 0.1 mA, gradually increasing by 0.1 mA, up to 2 mA. Fascicles which showed intense contraction with a lower threshold and correlating clinically with severity of spasticity and voluntary control were considered for ablation. About one-third (1/3) to three-fourth (3/4) of the fascicles of the dissected branches were ablated. The proximal stump was clipped using a silver clip. All the dissected neural tissue, prior to coagulation, was dipped in saline to avoid heat dissipation and then the sectioned proximal stumps were coagulated using bipolar coagulation to make the stump brown colored. If the stump is undercoagulated (white) it may regenerate and if the stump is over coagulated (black) then it may get auto amputated and may regrow. Clipping of the stump was performed to identify the dissected branches in cases of re-exploration and probably may also help in decreasing the incidence of the re growth. The limb was immobilized using slab across the joint. The slab was applied for a period of 2 weeks and gradual active exercises were begun later.

Results

A total of 24 patients were operated from January 2008 to December 2009 among whom 4 patients did not complete 6 months of follow-up. Therefore, the results of remaining 20 patients were analyzed using SPSS 16 and are as follows:

Age and gender distribution

Number of patients under and above 18 years of age were 17 and 3 respectively [age ranging from 5 to 35 (mean – 12.85) years]. The male to female ratio was 8:12 [Figures 2 and 3].

Figure 2.

Age distribution

Figure 3.

Gender distribution

Eleven patients underwent SMF of the musculocutaneous nerve for elbow flexor spasticity, among whom two patients have undergone bilateral SMF of this nerve. Twenty patients underwent SMF of the median nerve for pronator spasticity, among whom four patients underwent bilateral SMF of this nerve. Nineteen patients underwent SMF of the median nerve for wrist flexor spasticity, among whom four patients underwent bilateral SMF of the median nerve. Three patients in the same group also underwent SMF of the ulnar nerve.

The results on spasticity of various targeted muscles, selective voluntary control and functions have been shown in Table 4 and in Figures 4–9.

Table 4.

Outcome

Figure 4.

Results on elbow flexor spasticity

Figure 9.

Results on selective voluntary control of wrist flexors

Figure 5.

Results on selective voluntary control of elbow

Figure 6.

Results on pronators spasticity

Figure 7.

Results on selective voluntary control of pronators

Figure 8.

Results on wrist flexor spasticity

Results of SMF on functional evaluation

Wee FIM Scale was impaired in 11 children. The mean pre-op and post-op Wee FIM scores were 105.7 and 110.5 respectively. The mean increase in score was 4.85 (P = 0.001). Self-care domain of Wee FIM scale was also analyzed to meet with the objectives of the study. The mean pre-op and post-op scores of this domain were 32.15 and 35.45 respectively. The mean increase in score was 3.3 (P = 0.0015)[Figure 10].

Figure 10.

Self-care domain

The functions of the intrinsic muscles of the hand (opposition, pinch, and grasp) were evaluated. There was improvement in opposition and pinch functions in second and third fingers. However, it did not reach statistical significance. The P value for the ability to grasp a 2” rod was significant (0.016). The ability to grasp a rod lower than 2” diameter was not significant (P = 0.062 for 1 inch rod and P = 0.25 for half inch rod) [Figure 11].

Figure 11.

Results on hand functions

Discussion

In general the recommended treatment of spasticity is to try first nonablative measures like therapeutic exercises, use of splints and orthotics, usage of medications, nerve blocks, and muscle injections to produce helpful muscle tone. However, the surgical measures (the ablative procedures) like soft tissue release and neural fasciculotomies (neurotomies) are necessary only when the spasticity does not respond to these modalities. All patients in the study were planned for surgery when they showed no further reduction in harmful spasticity to nonablative measures.

In this series (n=20) all patients had spasticity due to cerebral palsy. Most of the patients were under 18 years of age. Many of them have come late (later than 4- to 6-year age) because of late referrals and various social, economical, educational, and geographic constraints. All patients in this series had normal intelligence or minimal mental sub normality.

Spasticity outcome

Elbow flexor spasticity

The reduction in elbow flexor spasticity following SMF of the musculocutaneous nerve (n=13) was significant in all the patients (n=11) with five developing normotonia. All patients had improvement in selective voluntary control and cosmetic appearance. There were associated benefits of surgery on shoulder joint movements. There was relief in elbow flexion dynamic (on activity) spasticity (n=5) which manifested during activities like walking.

Garland et al. performed complete musculocutaneous neurectomy in adult patients with stroke by which they produced complete denervation of biceps and brachialis. They showed improvements in spasticity, cosmetic appearance, and personal hygiene. In recent studies, preoperative planning and perioperative electrostimulation helped to quantify the fascicular ablation rather than complete neurectomy to achieve better results. The senior author of the present series had reported 36% of residual spasticity following musculocutaneous nerve SMF with limited (50% or less) fascicular ablation. In the present series we report greater reduction in spasticity (mean postoperative Modified Ashworth's Scale – 0.73) which was comparable with Marrawi et al. (mean postoperative Ashworth's Scale – 0.8) following more fascicular ablation as seen in Tables 5 and 6.

Table 5.

Comparative study of Marrawi et al. and present series

Table 6.

Comparative analysis of upper limb selective motor fasciculotomies

Pronator spasticity

The reduction in pronator spasticity following SMF of the median nerve (n=24) was significant in all the patients (n=20), however, not to the extent of elbow flexor spasticity reduction. The mean postoperative spasticity on Modified Ashworth's Scale was 1.46, which was higher when compared to that of Marrawi et al. (Ashworth's Scale was 0.6) [Table 5]. Even then there was improvement in selective voluntary control and self-care domain on Wee FIM Scale in the present series.

Wrist flexor spasticity

The reduction in wrist flexor spasticity following SMF of the median (n=23) and ulnar nerves (n=3) was significant in all the patients. The mean postoperative spasticity on Modified Ashworth's Scale was 0.74 (whereas on Ashworth's Scale 0.48 in Marrawi et al. series) [Table 5]. This has resulted in improvement in selective voluntary control and self-care domain of Wee FIM Scale, i.e., eating, dressing, grooming, toileting, and bathing.

None of the patients needed soft tissue release surgery.

Functional outcome

Hand functions

Distal effects of surgery on the pronators and wrist flexors were seen in the form of improved hand functions like opposition, pinch, and grasp. Grasping to large objects improved more than other functions. Improvements were noted more often in the index and the middle finger (median nerve) than the ring and the little finger (ulnar nerve). This could be explained because we have performed median nerve SMF more often than both median and ulnar nerves together.

Functional activities

The self-care activities improved following surgery in all patients. Thirty-three percent of patients showed improvement from dependence to complete independence in performing self-care activities.

Cosmetic outcome

All patients improved cosmetically following the reduction in spasticity. They were having better look of the limb while performing self-care activities, walking and during leisure time.

The operative scars of musculocutaneous nerve SMF were cosmetically acceptable as they were hidden under the arm sleeves.

In the present series the SMF of the median nerve was performed by a horizontal skin crease incision unlike the linear incision parallel to long axis of the limb carried across the joint as described in other series. There was hardly any visible scar in most of the patients of the present series.

Follow-up

There was no recurrence during the mean follow-up period of 10 months (ranging from 6 to 24 months) despite ablating the fascicles close to the muscle.

Complications

The incisions and the tissue (including neural) handling techniques described earlier prevented development of any scar contractures and wound complications.