Nerve Entrapment Syndrome

8/3/2019 Nerve Entrapment Syndrome

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Increased pressure on a nerve as it traverses a closed space causes an

entrapment neuropathy. The mechanism of nerve damage is not completely understood but

includes pressure, friction and ischemia. There are three major manifestations of nerve

entrapment:

1. Pain

2. Paresthesia3. Weakness distal to the site of entrapment

RADIAL NERVE ENTRAPMENTS The radial nerve can be compressed at several

locations:

--The axilla

--The spiral groove

--The elbow

--Below the elbow

High radial nerve palsy Compression of the radial nerve in the axilla (eg, by pressure with

the arm hanging over the back of a chair) causes weakness of all the muscles supplied bythe nerve, including the triceps. Thus, patients typically display weakness of wristextension,

stiffness in the dorsal arm and forearm, and an inability to extend the little finger. Sensory

changes are very mild and localized to a small area on the back of the hand between the

thumb and index finger. The condition is usually transient and does not require

therapy; surgical exploration and decompression should be considered if

triceps weakness persists and EMG studies reveal denervation of this muscle group.

However, surgical results are often poor.

'Saturday night palsy' is a term sometimes used to refer to radial nerve compression that

results from binge drinking of alcohol and the subsequent prolonged immobility associated

with alcohol-induced stupor. Such patients typically have an injury to the nerve as ittraverses the spiral groove.

Transient compression has been described in tennis players and may occur from entrapment

by the lateral head of the triceps. Features are similar to radial

tunnel syndrome with weakness of wrist extension, stiffness in the dorsal arm and forearm,

and inability to extend the fifth digit against resistance. Electrodiagnostic studies reveal

denervation of the triceps in this setting. Surgical decompression may be necessary

when weakness is detected. In contrast, injuries in the spiral groove spare the triceps since

it is supplied more proximally.

Radial tunnel syndrome

The radial nerve pierces the lateral muscular septum wherecompression may cause pain and tenderness in the area of the lateral epicondyle (the radial

tunnel syndrome). Other symptoms include sensations of popping, paresthesia, and paresis.

In one series of 79 patients the most common symptoms were 'deep aching' in the forearm,

radiation of pain to the neck and shoulder, and a 'heavy' sensation of the affected arm.


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True neurogenic radial tunnel syndrome is an uncommon condition caused by entrapment of

the radial or posterior interosseous nerve in the radial tunnel and is usually easily

identifiable by focal motor weakness in the distribution of the posterior interosseous nerve.

The term "radial tunnel syndrome" is best reserved for the truly neurogenic cases.

Causes of radial nerve entrapment in the elbow region include congenital anomalous

structures, trauma, compression within a fibrous arcade of Frohse, compression by the

supinator muscle, or compression against a bony prominence. A study carried out in three

factories in France compared 21 patients with controls selected from workers in the same

plant associated radial tunnel syndrome with tasks that required full extension of the elbow,

a twisted posture of the forearm, or hard manual labor that required forceful and repetitive

movements involving elbow extension and forearm pronation and supination. Personal

activities, household chores, and sport and leisure activities were not contributory factors

Several maneuvers may suggest the diagnosis of radial tunnel syndrome:

--The pain may be reproduced by passive stretching or resisted extension of the middle

finger, or by resisted forearm supination with an extended elbow

--Palpation may generate intense tenderness over the posterior interosseous nerve under

the proximal edge of the superficial head of the supinator muscle, approximately 5 cm distal

to the lateral epicondyle

--Application of a tourniquet above the area of pain may produce pain and paresthesias

--Tapping over the radial head just distal to the lateral epicondyle may produce tingling

along the course of the nerve (Tinel's sign)


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Electrodiagnostic tests are often normal when the compression is intermittent. In one series

that included 79 affected limbs, no consistent imaging findings were noted to be

diagnostically helpful

Most patients recover with rest and gentle exercise. The results of surgery areunpredictable, being successful in from less than one-half of cases to providing good to

excellent results in 97 percent. In one study, the results were worse in patients receiving

workers' compensation or pursuing litigation

As a diagnostic maneuver, I have injected the supinator region with local anesthetic. For

those who have symptomatic improvement, a glucocorticoid injection may provide longer-

term relief.

Below the elbow The purely motor posterior interosseous branch of the radial nerve

supplies the extensors of the wrist and fingers; it can be compressed from forceful

supination-pronation tasks or from carrying objects with the elbow fully extended. Amongathletes, those involved in racket sports and elite bodybuilders are at increased risk of

this neuropathy. Involvement is suggested by the inability to extend the little finger, with

sparing of the extensor carpi radialis longus so that the wrist can still be extended.

In addition to symptoms and electromyographic findings, ultrasonography may assist in

diagnosis. The deep branch of the radial nerve within the supinator muscle was were

significantly larger in anteroposterior and transverse diameter in four symptomatic patients

than in healthy volunteers

MEDIAN NERVE ENTRAPMENTS

The median nerve proper, or its motor branch theanterior interosseous nerve (which branches off below the elbow), can be compressed in the

elbow region.

--Median nerve entrapment by the pronator teres muscle (called the pronator

teres syndrome) may result in diffuse arm pain, weakness of wrist pronation, and

paresthesias along the median nerve distribution. The pronator teres muscle lies in the

antecubital fossa medially. The patient with nerve entrapment in this area typically

complains of an aching pain in the proximal forearm which may begin insidiously. It is

reproduced by resistance to pronation of the forearm and flexion of the wrist, or by a

tourniquet test over the pronator teres muscles with compression for 30 seconds.


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--Patients with anterior interosseous involvement do not experience sensory

loss; weakness is confined to the pronator quadratus, flexor pollicis longus, and the flexor

digitorum profundus to the middle and index fingers. Thus, the typical pattern is loss of

distal flexion of the thumb and index finger, giving a characteristic flattened pinch sign.

Nerve entrapment in this region typically is due to elbow trauma, repetitive elbow flexion, or

supination and pronation of the forearm. Occasionally compression is caused by aberrant or

accessory muscles, a fibrous band beneath the pronator teres, or pressure from an enlarged

bicipital bursa. In one case entrapment was due to a peripherally inserted central catheter

(PICC).

The differential diagnosis for these syndromes includes carpal tunnel syndrome which can

cause retrograde paresthesia into the forearm, and occasionally to the shoulder.

Electrodiagnostic studies may aid in the distinction in difficult cases

Rest, splinting the elbow, avoidance of repetitive forearm motions, and work simplification

are often sufficient treatment for median nerve entrapment. Nonsteroidal antiinflammatory

drugs also may provide pain relief. Injection into the tender sites of the pronator teres

muscle with a corticosteroid and local anesthetic agent (10 to 20 mg of methylprednisolone

acetate, and 1 mL of 1 percent lidocaine hydrochloride using a #23 or #25 needle) is useful

if pain persists. Surgical decompression is helpful if the disability persists for several months

despite these measures, and if the site of entrapment is established.

LATERAL ANTEBRACHIAL CUTANEOUS NERVE ENTRAPMENT Entrapment of the

lateral antebrachial cutaneous nerve can be induced by trauma; compression occurs within

the biceps tendon and brachialis muscle. Patients usually present with pain and paresthesia

from the elbow crease to the thenar eminence, along the radial side of the forearm.

Patients often experience symptom relief after injection of lidocaine hydrochloride into the


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region of the bicipital tendon and the elbow crease; this is a useful diagnostic test. Sensory

nerve conduction confirms the neuropathy. Surgical decompression is recommended

ULNAR NERVE ENTRAPMENT Ulnar nerve compression may occur at the elbow within

the epicondylar groove or just distal to that site in the cubital tunnel. At either of theselocations symptoms of ulnar nerve palsy include pain and paresthesia along the medial

forearm, wrist, and 4th and 5th digits. Associated muscle weakness can progress to muscle

atrophy of the intrinsic muscles of the hand, and flexion contracture of these two digits

(ulnar claw hand).

Compression in the epicondylar groove The most common site of compression is at the

epicondylar groove. Leaning on elbows at work, when driving, or using the elbow to push up

when arising from the bed are frequent causes. Simply altering arm position alleviated the

problem in 12 of 24 patients followed for one year

Other causes include compression by ganglions; ganglions associated with osteoarthritis of

the elbow joint; or constricting bands. Patients with end-stage renal disease receiving

hemodialysis appear to have a high prevalence of ulnar neuropathy; multiple factors

including pre-existing polyneuropathy and dialysis-related arm positioning may play a

causative role.

Perioperative ulnar neuropathy due to positioning may occur. In a prospective series of 203

consecutive patients undergoing orthopedic surgery, three percent developed ulnar

neuropathy. The incidence was six percent in patients having total hip arthroplasty. Therewas a highly significant association between a tilted body position on the operating table

and development of ulnar neuropathy on the contralateral side. This position rotates the

arm internally and places the ulnar nerve at risk for direct compression.

Compression at the cubital tunnel The cubital tunnel is a fibroosseus canal formed by

the medial condyle, ulnar collateral ligament, and flexor carpi ulnaris muscle. Elbow flexion

decreases the volume of the channel. Compression of the ulnar nerve as it traverses the

elbow may be a complication of repeated local trauma, or constriction and entrapment in

the cubital tunnel, the cubital tunnel syndrome.

The entrapment is due to a structural narrowing of the tunnel, often following a direct blowto the upper limb (not necessarily the elbow alone) combined with excessive elbow

compression caused by chronic pressure over the ulnar groove. The latter can be due to

occupational stress, unusual elbow positioning, or using the elbow to arise from bed or a

chair. Subluxation of the nerve, which commonly occurs in otherwise normal individuals,

may predispose to scar tissue in the tunnel. In addition, repetitive movements with elbow

flexion and extension (eg, hammering) may cause compression at the humeroulnar arcade,

a dense fibrous archway joining the two heads of the flexor carpi ulnaris muscle


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Antecedent trauma is very common. As an example, in one series of 145 operated patients,

over 80 percent followed a causative event . Also notable in this study was a 4.5 to 1 male

to female ratio, the presence of an elbow flexion contracture in 52 percent, and firm ulnar

nerve adhesions in 73 percent of those undergoing surgery.

Cubital tunnel syndrome presents with paresthesias along the lateral forearm, wrist, and

fourth and fifth digits; it may be bilateral. A positive Hoffman-Tinel test (tapping over the

nerve) helps locate the site of entrapment, often at the ulnar groove. Pain also may be

reproduced by directly palpating the nerve.

Many patients have atrophy of the intrinsic muscles, weakness in pinch and grasp, and

sensory loss at the ulnar side of the fifth finger. There also may be wasting of the

hypothenar muscles and flexion contracture of these digits.

Compression at the wrist Compression of the ulnar nerve may occur at the wrist in

Guyon's canal. While symptoms may be similar, the distal location of the neuropathy sparesthe deep flexors of the 4th and 5th digit flexors.

Management Conservative therapy is the initial approach in the absence of significant

motor weakness. Avoidance of prolonged elbow flexion and compression may be sufficient.

If the patient needs to change the manner of getting up in bed, suggest a rope tied to the

foot of the bed, carried up over the covers, with a loop on the end so the patient can use

this to pull up and avoid pushing with the elbow.

Local corticosteroid injection along the ulnar groove may be effective, particularly if

compression is due to inflammatory lesions such as rheumatoid synovitis. Using a No. 25

3/4-inch needle, a mixture of 1 mL lidocaine hydrochloride and steroid (methylprednisolone20 to 40 mg) is injected cautiously into the groove, parallel with the nerve. The patient

should be asked if there are any sensations of nerve penetration when the needle is inserted

so that injection into the nerve trunk can be avoided.

Electrodiagnostic study is valuable to establish the site of compression if conservative

measures fail; the readily accessible location of the entrapment area permits direct testing

of sensory and motor conduction across the cubital tunnel. Radiographs may reveal

osteophytes impinging on the area. MR imaging of this area can be useful, although it is

often difficult to interpret and is expensive

Significant disability or weakness often are indications for surgery. Several procedures areavailable, with the choice depending upon the severity of compression. Surgery should not

be delayed since the results are less satisfactory when the condition has persisted for one

year or longer

Surgical decompression with endoscopal assistance may be the preferred procedure. One

study evaluated the results in 76 patients in whom 85 elbows were subjected to the

procedure. At a mean follow-up of 32 months, results were excellent, good, fair, or poor in


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42, 45, 11, and 2 percent, respectively. Recurrence occurred in 3 elbows, and there were no

serious complications. The procedure is recommended for patients with mild to moderate

symptoms. Preoperative absence of ulnar sensory action potential and the presence of long-

standing cervical disease were associated with poorer outcomes in one study; persistent

postoperative pain, paresthesia, and impaired two-point discrimination were more frequent

in patients with these risk factors.

Functional recovery is generally good following surgery. This was illustrated in a series of

460 patients who underwent a variety of decompressive procedures; 92 percent had a

'good' functional outcome.

Nerve Entrapment Syndrome

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