A Functional Approach to Median Nerve Entrapment: A Case Report

A Functional Approach to Median Nerve Entrapment: A Case Report

Davis, Ardee Frizzell

Abstract

Objective: To discuss the case management of a patient with an upper extremity repetitive stress disorder that resulted from median nerve entrapment. The case was successfully treated with a functional approach, using manipulation/mobilization, an officeand home-based rehabilitative system, and nutritional intervention.

Clinical Features: A 42-year-old woman presented with a recurrent episode of forearm pain and carpal tunnel-like symptoms radiating into her right wrist, hand, and fingers. The onset of symptoms was approximately 3 years prior to presentation with episodic exacerbations related to repetitive stress activity to the affected area. Needle electromyography and nerve conduction velocity studies were positive for confirming the carpal tunnel diagnosis. There was also a grip strength deficit on the dominant right side.

Intervention and Outcome: The patient was treated for her initial condition and subsequent recurrences with muscle relaxants, analgesics, and corticosteroids. She also utilized a wrist splint to reduce pain and provide support. The patient reported that she had several unpleasant side effects with medications and discontinued usage. She reported minimal improvement of her condition with the physical therapy regimen (primarily passive therapies such as ultrasound). Patients suffering from median nerve entrapments are seldom referred for rehabilitation. Her complaints were dramatically improved after a 6-week active-care rehabilitation program, which included chiropractic manipulation/mobilization, office-home rehabilitative exercises, and nutritional intervention.

Conclusion: This case highlights the importance of conducting a thorough examination to differentiate the exclusive diagnosis of carpal tunnel syndrome from other potentially concomitant median nerve entrapment syndromes. Following a comprehensive examination, the pronator teres was also implicated in the patient’s symptoms. A multi-dimensional approach using chiropractic care, an office-home rehabilitation system, and nutrition contributed to the successful outcome objectives of reducing symptoms, restoring function, reducing reliance on medication, and preventing possible surgery. In addition, the patient received knowledge specific to her condition, home equipment, and documentation guidelines to track and maintain post-treatment progress.

Key words: Median nerve entrapment, repetitive stress syndrome, chiropractic, rehabilitation

Introduction

Carpal tunnel syndrome occurs when the median nerve becomes entrapped in the area of the volar wrist canal beneath the flexor retinaculum.1 Pronator teres syndrome occurs with entrapment of the median nerve as it courses through the pronator teres muscle or the arch formed by the two heads of the flexor digitorum superficialis.2 Both median nerve entrapment disorders can cause neural symptoms to the hand, wrist, and upper extremity.1,2 The neural symptoms can be described as paresthesias, which are increased sensations like pins and needles. The patient can also report a feeling of numbness or a loss of sensation called hypoesthesias (Fig. 1).

The median nerve possesses both sensory and motor fibers. It is formed along the lateral wall of the axilla by the confluence of the medial (C5-C7) and lateral (C8-T1) cords of the brachial plexus.1 Motor innervation includes the thenar region, the elbow joint, anterior forearm, intrinsic muscles of the hand, and the first two lumbrical muscles. The sensory innervation includes the dorsal and palmar area of the thumb, index, and middle finger, along with the radial side of the ring finger.3-7

Carpal tunnel and pronator teres syndrome are specific diagnoses that can result from repetitive stress to the median nerve and contiguous anatomical structures that are kinetically affected. They are two disorders that can also be classified as repetitive stress, overuse, and cumulative trauma disorders.3 In fact, of the 12 million repetitive stress injuries each year, it is estimated that 60% involve carpal tunnel syndrome.8 According to the U.S. Department of Labor, carpal tunnel syndrome is a chief occupational hazard and leading cause of lost work days, costing industry over $100 billion per year.8 Although nerve conduction velocity and needle electromyography are considered the gold standard for confirming a carpal tunnel diagnosis,2 other nerve entrapment and tendon-related disorders should also be considered when evaluating the upper extremity. Since the upper extremity contains numerous muscles, ligaments, blood vessels, and nerves, it is imperative that these structures receive adequate consideration in an evaluation before settling exclusively on a carpal tunnel syndrome diagnosis. Typical management of carpal tunnel syndrome, pronator teres syndrome, and other repetitive stress conditions includes analgesics, anti-inflammatory medications, corticosteroids, and even surgery if conservative management is unsuccessful. The objective of this case report is to delineate common muscular and kinetic chain imbalances that occur in the forearm and wrist and contribute to median nerve entrapment syndromes. If the correct anatomical structures are identified, a comprehensive treatment approach can be developed to provide appropriate functional restoration.

Case Report

A 42-year-old woman, height 5’5″, weight 145 lbs., reported an acute recurrence of forearm and carpal tunnel pain that radiated from the mid-section of her forearm and into the thenar eminence and first three fingers. Carpal tunnel syndrome is more common in women and is bilateral in 50% of cases.9 Unlike carpal tunnel syndrome alone, however, her symptoms developed approximately mid-forearm and traveled distally to her fingers. The symptoms were steady in intensity throughout the day, but worsened at night. This finding is consistent with carpal tunnel patients who report nocturnal symptoms 95% of the time.9 In comparison, patients with pronator teres syndrome usually do not report nocturnal symptoms, as much as symptoms initiated by repetitive pronation and supination of the forearm.

Several years prior to presentation, the patient’s symptoms were mild in nature. Shaking her wrists and hands would provide relief; however, over the past year, she reported no relief with hand movements. In carpal tunnel cases, patients will commonly report relief with rapid hand movements. This test is descriptive of the Flick sign and is specific to carpal tunnel patients in 93% of cases.” The patient reported perceived weakness of her dominant right side, although the dominant side is usually 10 to 15% stronger than the non-dominant side.10 Strength loss by areas supplied by the median nerve is a common occurrence with both carpal tunnel and pronator teres syndrome.11 Follow-up examination of her right wrist revealed a 30% decrease in grip strength when compared with her left side.

As a laboratory microbiologist for 9 years, the patient used her right upper extremity extensively to transfer pharmaceuticals into test tubes for drug trials. Although her condition began insidiously, a recent project involving repetitive pronation and wrist flexion caused a heightening of the irritation and symptoms in the affected areas. The patient was provided with a wrist cock-up splint at work, but reported little relief with usage. She received an ergonomie evaluation of her worksite and job responsibilities; however, the alterations had no favorable impact on her condition. The patient’s primary care physician referred her to a neurologist for a nerve conduction velocity study and needle electromyography. The findings were consistent with the diagnosis of right-sided carpal tunnel syndrome.

The patient’s family, medical, and social histories were non-contributory to her current condition. She presented with swelling and spasms of the right forearm and wrist and mild atrophy of the right thenar eminence. On a visual analog pain scale, she rated her symptoms as 8/10. The initial carpal tunnel syndrome questionnaire indicated severe impairment/disability. There was no evidence of skin changes or warmth in the wrist or forearm region.

Examination of the cervical, thoracic, and upper extremity was performed. Orthopedic tests, such as Phalen’s, Tinel’s, and carpal compression, were positive for carpal tunnel syndrome. These tests are good indicators for carpal tunnel syndrome, but are not completely reliable. The electrodiagnostic tests of nerve conduction velocity and needle electromyography are more specific for confirmation of the carpal tunnel syndrome diagnosis.12 There was a positive Tinel’s sign over the volar surface of the wrist and the pronator teres muscle. The biceps, brachioradialis, and triceps reflexes were graded at 2/2 bilaterally. Muscle strength in the upper extremities was 5/5 bilaterally. Grip strength evaluated with the Jaymar dynamometer was decreased 30% on the right side. Decreased sensation by pinwheel testing was evident in the right forearm, thenar region, and first 3 fingers. All other cervical, thoracic, and extremity orthopedic and neurological tests were negative.

Plain films of the cervical spine and a bilateral wrist series were performed. Cervical imaging revealed a loss of the cervical lordosis and disc space narrowing at C4-5, C5-6, and C6-7 with mild degenerative changes along the vertebral endplates. The bilateral wrist series was normal. Erythrocyte sedimentation rate, C-reactive protein, and rheumatoid factor laboratory tests were within normal limits.

The patient was normal in gross appearance; however, there was a bilateral gothic shoulder presentation and a forward-drawn head posture. Static and motion palpation of the spine and upper extremity revealed decreased ranges of motion at multiple levels of the cervical spine and of the right wrist particularly in flexion and extension, compared with the left. There was hypomobility of the right hamate bone with motion palpation. Further examination revealed decreased thumb adduction and right thenar atrophy.

The acute inflammatory phase of treatment started with sequential electrical muscle stimulation and ice therapy for the first 72 hours. The goal was to reduce muscle spasms and inflammation and produce endorphins necessary to combat pain. The next step included continuous ultrasound, massage, and heat. Grade I mobilization of the wrist and forearm was performed to improve ranges of motion and to reduce active trigger point activity. During all phases of care, spinal and upper extremity manipulation was performed based on static and motion palpation findings through diversified adjusting techniques. George’s Test was performed to rule out any vertebrobasilar insufficiency prior to cervical spine adjusting.12

Following the anti-inflammatory phase of care (weeks 1 and 2), the patient was introduced to the Wristiciser-PROplus(TM) Treatment System. This rehabilitation system is specific to the upper extremity with progressive exercise protocols, user-friendly equipment, and documentation guidelines to monitor progress. It utilizes weight bags and elastic tension bands of varying resistance to perform stretching and strengthening of key muscle groups. Recent research has shown that one of the primary objectives in achieving muscle balance in the forearm can be obtained through strengthening the posterior forearm muscles and stretching the anterior forearm muscles.” Wrist flexion, uncontrolled and/or beyond normal parameters, decreases the space available to the median nerve; wrist extension increases the space available to the median nerve.3-7

The first phase of care is called the stretching phase. The patient was treated with 4 targeted exercises: the wrist rock and stretch (Fig. 2), transverse carpal ligament stretch, the thumb/wrist press and turn, and the dual thumb press.11 These exercises help to re-establish the kinetic link between the median nerve and the surrounding musculature. The wrist rock and stretch allows for gliding of the median nerve in the carpal tunnel through the anterior forearm and between the heads of the pronator teres, beginning with wrist flexion, and progressing to wrist extension as warranted. This controlled rocking motion lessens irritation and inflammation of the median nerve. The transverse carpal ligament stretch is designed to take advantage of the viscoelastic nature of the ligament itself and provide it with gentle controlled stretching. This is significant because the transverse carpal ligament and the semi-circular arrangement of carpal bones define the boundaries of the carpal tunnel.6 The thumb/wrist press and turn stretches the pronator and supinator muscles, thereby improving ranges of motion. Since repetitive supination and pronation of the forearm can initiate pronator teres symptoms, stretching the pronator and supinator muscles helps to re-establish balance between these agonist and antagonist muscles and reduce the likelihood of irritation. The dual thumb press (Fig. 3) stretches the anterior compartment of the forearm and the transverse carpal ligament.

The remaining exercises in this phase of care involve stretching the posterior forearm muscles and allowing for the median nerve to glide through the various compartments of the forearm. Since irritation to the median nerve can cause carpal tunnel and/or pronator teres syndromes, reducing it remains an important objective throughout the course of treatment.

The next phase of care is called the strengthening the phase. It begins at approximately week 3 and transitions beyond patient discharge into the maintenance home care program. Prior to advancing to this phase of rehabilitation, the patient is prescribed a home unit. This allows the patient to receive supervised office visit instruction and to continue the customized program at home. Most of the exercises are performed for 1 to 3 sets for a count of 5 to 10 seconds. Between sets, there is a 1- to 2-minute rest and the protocols are prescribed 2 to 3 times daily. All exercises are performed within the patient’s pain-free ranges of motion and are not intended to exceed the patient’s abilities and tolerance. In addition, the system allows for documentation of the patient’s response to care and establishes benchmarks for advancing to more challenging exercises.

There are 6 targeted strengthening exercises in the Wristiciser System for carpal tunnel and pronator teres syndromes including thumb flexion, adduction and opposition strengthening, pronator/supinator strengthening, wrist flexion curls, wrist extension curls, and broomstick exercises palm up and palm down.11 These exercises are designed to re-establish kinetic balance between the pronator and supinator muscles, the wrist flexors and extensors, and the thenar muscles (Fig. 4). In addition, these exercises are designed to improve carpal-metacarpal joint range of motion and grip strength, improve circulation, and reduce pronator teres trigger point activity. The remaining supportive exercises further strengthen the pronator and supinator muscles, as well as the antagonistic extensor muscles of the forearm, and help prevent the lumbricals from being pulled into the carpal tunnel with finger flexion. In addition, these exercises improve grip, biceps, and finger strength, and dexterity. Treatment is performed until the patient’s symptoms resolve, pain-free full range of motion is obtained, or progress reaches a plateau. Since carpal tunnel and pronator teres syndromes are often repetitive stress conditions, patients are encouraged to continue their supportive and preventive home care exercise program, even in the absence of symptoms.

The patient was encouraged to supplement daily with vitamin B6 and B-complex vitamins because these supplements have been shown to aid in nerve function and repair.13,14 The patient’s forward-drawn head posture was also addressed through chin retraction exercises-she was asked to retract her head into a small gym ball. This motion was helpful in strengthening the deep neck flexors and relaxing the tight suboccipital muscles of the neck. The patient was also instructed in postural reinforcement exercises by having her perform the Brugger relief position 3 to 5 times daily. The patient was asked to sit comfortably in a chair, feet a shoulder width apart, and breathe forcefully through the abdomen while retracting the scapula in a medial and downward direction, with the palms facing forward and thumbs pointing backward. Proper posture is essential in stabilizing the upper thoracic muscles like the overactive trapezius and the inhibited/weak levator scapula muscles commonly seen with a gothic shoulder presentation.

Muscular imbalances often occur in conjunction with median nerve entrapment syndromes. As soon as one muscle group predominates, it neurologically inhibits and weakens the opposing muscle group. Janda et al. explained that the basis for most muscle imbalances comes from our predictable response to stressful environmental demands (constrained postures, repetitive tasks, gravity stress, and inactivity.)10 According to Sherrington’s Law of Reciprocal Inhibition, when 1 muscle is shortened from overuse, as in the case of repetitive stress injuries, it will also mechanically reduce the range of motion of its antagonist muscle and neurologically inhibit it.10 This combination of biomechanical and neurophysiologic influences strongly stimulates the creation and maintenance of muscular imbalances. Neuromuscular re-education is an important goal in correcting the abnormal motor learning patterns and recruitment resulting from impaired sensory and motor information. A Wristiciser-ProPlus System helps to re-establish the development of normal motor learning patterns and muscle recruitment. Some of the benefits include improving range of motion and proprioception, correcting muscle imbalance, and normalizing movement patterns (Fig. 5).

The goal of the rehabilitation prescription is to activate inhibited muscles, stretch tight muscles, strengthen weakened muscles, and eliminate active trigger points. Proprioception and coordination exercises were also incorporated with the Wristiciser by establishing motor control and kinesthetic awareness. The patient moved the Wristiciser unit in the standing position in different planes of motion to improve proprioception, balance, and coordination. This movement was further challenged by adding weight bags and by performing these exercises with and without visual input. After the patient successfully completed this level, she performed these exercises on the rockerboard and round board for 2 minutes initially with the eyes open and then with the eyes closed. This level of challenge allowed for co-contraction of stabilizing and accessory muscles involving both the upper and lower extremities. Cross-training exercises were then introduced for both the upper and lower body providing challenge to the total body and thereby increasing strength and endurance. Following 6 weeks of active rehabilitation care, the patient’s reevaluation revealed normal grip strength measurements, improved postural biomechanics, and no pain/paresthesias in the forearm or wrist.

Discussion

The patient was initially diagnosed with a unilateral carpal tunnel syndrome. The pronator teres, however, was overlooked. Since entrapment of the median nerve in the wrist and pronator teres muscle produces similar symptoms, it is critical to evaluate both structures, especially for patients involved with repetitive stress occupations. Carpal tunnel release surgery is one of the most frequently performed surgical procedures in North America.1 In cases where an inaccurate diagnosis is made, the patient is left with a failed surgical result and a persistent symptomatic condition. Even though carpal tunnel syndrome is more commonly encountered than other median nerve entrapment syndromes, it remains overly diagnosed, misdiagnosed, or incompletely diagnosed.16 In fact, a recent study suggests that many patients with carpal tunnel syndrome have been found to have a nerve compression at a higher, more proximal level, such as the elbow.16 This finding supports the rehabilitation prescription as a viable option in the management of median nerve entrapments because the localization of compression is often elusive. In such cases, correcting muscle imbalances, re-establishing normal motor learning patterns, and improving ranges of motion may offer relief to many and reduce the need for surgery.

The clinical presentation of carpal tunnel and pronator teres syndrome are very similar. They include pain in the wrist and forearm regions, weakness of the thenar muscles, and numbness/paresthesias of the radial three and a half fingers. If the patient has pronator teres syndrome exclusively, there is generally no nocturnal pain, no nerve conduction delay at the wrist location, and examination of the wrist reveals a negative Tinel’s sign. Provocative testing of the pronator teres and palpation of the forearm are also beneficial in isolating the level or levels of compression. Provocative testing is performed by having the patient resist pronation with the forearm in a neutral position as the elbow is gradually extended or with repeated pronation/supination movements. Palpation of the forearm generally reveals tenderness and firmness over the pronator teres muscle. Needle electromyography and nerve conduction velocity studies may also differentiate the level of median nerve entrapment.

Other differential diagnoses that should be considered include cervical radiculopathy, thoracic outlet syndrome, double-crush syndrome, brachial plexus neuropathy, and polyneuropathy. The patient’s vascular system should also be evaluated to rule out Raynaud’s Phenomenon. Raynaud’s Phenomenon is usually brought on by cold or stress and is treated with warmth or, in severe cases, medications to dilate blood vessels. A thorough history is important to rule out carpal tunnel symptoms resulting from pregnancy, contraceptive use, hormonal or endocrine disorders, or an array of other non-biomechanical etiologies. Laboratory tests may help if rheumatoid arthritis, lupus, and gout are suspected because these conditions may contribute to median nerve neuropathies. Thoracic outlet orthopedic tests may help to distinguish any neural or vascular causes for the presenting symptoms. The presentation and physical findings of median nerve entrapments require a keen eye because not all results are “classic,” and laboratory and electrophysiologic results are often equivocal.

The anterior interosseous nerve should also be evaluated because it is a branch of the median nerve that affects the thumb, index, and middle finger. Anterior interosseous nerve syndrome manifests as paresis/paralysis commonly affecting pinch strength. This often leaves the patient complaining of difficulty with writing or picking up small objects. Other orthopedic tests to consider include Finkelstein’s test to rule out stenosing tenosynovitis of the abductor pollicis muscle and Froment’s sign to rule out weakness of the adductor pollicis muscle or ulnar nerve paralysis.

Conclusion

The carpal tunnel diagnosis rarely exists exclusively. It is usually part of a larger repetitive-use syndrome that can result from muscle imbalances. These muscle imbalances often perpetuate the carpal tunnel and pronator teres symptoms because there is a range-of-motion deficit, repetitive stress, and irritation to anatomical structures. It is, therefore, critical that the diagnostician approach carpal tunnel symptoms with a more inclusive assessment that evaluates the entire upper extremity and cervical spine. Accuracy in this evaluation can lead to a prescription of office-home rehabilitation exercises that aim to restore function and limit disability. This treatment approach may reduce unnecessary surgeries and help to rehabilitate the post-surgical patient who has scar tissue, decreased ranges of motion, and faulty movement patterns. In addition, successful case management requires patient compliance through active participation in all phases of care.

Acknowledgment

The author thanks George Petruska, DC, DACRB, and Sidney Maycock, Jr., DC for their support and use of clip art in the preparation of this case report.

References

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Ardee Frizzell Davis, DC

Private Practice, Somerset, New Jersey

Copyright American Chiropractic Association Nov 2004

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