CERVICAL RIB SYNDROME

The cervical rib usually arises from the seventh cervical vertebra and is the most common cause of neurovascular compression at the base of the neck (Fig. 4-3). The condition may be bilateral. The rib or its fibrous extension narrows the interval between the anterior and middle scalene muscles and produces a higher barrier over which the neurovascular structures must arch on their way into the arm. In older patients or those with muscular weakness, the shoulder may also sag more than normal, which further increases the tension on the neurovascular structures. The compression may also be increased by carrying a heavy object.

Fig. 4-3 A, Compression caused by a cervical rib (arrow). B, Abnormal scalene muscles that may cause compression at the cervicobrachial region (arrow).

In the absence of a cervical rib, compression can occur between the middle and anterior scalene muscles because of abnormal insertions or the presence of additional muscle slips in the interscalene interval (scalenus anticus syndrome).

The lowest components (C8, T1) of the plexus are most commonly involved because of their position against the rib. The symptoms therefore tend to be most noticeable in the hand and inner aspect of the forearm. Pain and paresthesias may develop along the distribution of the ulnar nerve. There may be weakness, numbness, or clumsiness in use of the hand. Coldness, Raynaud’s phenomenon, or even gangrene may be the initial symptom.

Clinically, the cervical rib may be palpable, and the brachial plexus is often tender. Weakness and atrophy of the muscles supplied by the lower trunk (interosseous, hypothenar muscles) are occasionally seen. Sensation may be diminished over the ulnar aspect of the forearm, arm, and the ulnar 1½ fingers. Swelling, coldness, cyanosis, trophic skin changes, and other signs of circulatory insufficiency are occasionally observed.

Provocative positioning tests are often described in the assessment of thoracic outlet syndromes. Adson’s test may be positive in cervical rib and scalenus anticus syndromes (Fig. 4-4). This test takes advantage of the fact that by tensing the scalene muscles the interval between them is decreased, and any existing compression of the subclavian artery is increased. The test is performed by having the patient breathe deeply, extend the neck, and turn the chin toward the affected side. When the test is positive, a decrease in the radial pulse is noted, and pain is reproduced. If the test is negative, it is repeated with the chin turned to the opposite side. Although a positive test result is suggestive of compression in the interscalene region, it is often positive in the normal population and is not necessarily diagnostic of cervical rib or scalenus anticus syndrome. Symptoms can also be reproduced occasionally by exercising the fingers with the arms elevated (Fig 4-5).

Fig. 4-4 Adson’s test. It should be repeated with the chin turned the opposite direction.

Fig. 4-5 Elevated arm stress test. With the arms held overhead, the hands are opened and closed. A positive test result is pain and fatigue within 30 seconds.

Roentgenographic examination may reveal an extra rib extending from the transverse process of the seventh cervical vertebra (Fig. 4-6). The rib may be fully developed or rudimentary, and it is often bilateral. Its presence does not necessarily imply that it is symptomatic, however, because cervical ribs are often present in asymptomatic individuals.

Fig. 4-6 Bilateral cervical ribs (arrows).

Electromyography and nerve conduction studies are not useful in the diagnosis of any of the thoracic outlet syndromes. Vascular studies are occasionally helpful if diminished pulsations and reproduction of the neurologic and/or vascular symptoms occur during one of the various maneuvers. They are required if the initial findings suggest venous or arterial compromise.

COSTOCLAVICULAR SYNDROME

The space between the clavicle and the first rib may be narrowed by downward and backward pressure on the shoulders for a prolonged period of time. Abnormalities of the clavicle, such as malunion or nonunion after fracture, may contribute to the narrowing.

The syndrome is occasionally seen in individuals who are required to carry heavy packs on their shoulders. Intermittent numbness and pain in the hand and arm are the most common symptoms. These symptoms may be reproduced by the costoclavicular maneuver (Fig. 4-7). In this test, the shoulders are drawn downward and backward, and any change in the radial pulse or reproduction of symptoms is noted.

Fig. 4-7 The costoclavicular maneuver. The radial pulse may be diminished in many normal individuals.

HYPERABDUCTION SYNDROME

Neurovascular symptoms may also follow prolonged assumption of the position of shoulder hyperabduction. This position is often assumed during sleep and in certain occupations such as overhead painting. The neurovascular structures are compressed as they pass under the coracoid process and pectoralis minor muscle with the arm in hyperabduction (Fig. 4-8). Numbness and paresthesias are common, but the pain tends to be less severe than that seen in the other compression syndromes. Wright’s test (diminution of pulse or reproduction of symptoms on hyperabduction of the arm) may be positive (Fig. 4-9).

Fig. 4-8 Hyperabduction of the upper extremity that may produce neurovascular compression.

Fig. 4-9 Wright’s test.

TREATMENT

Patients with vascular complications should be promptly referred. Otherwise, the initial treatment is conservative. Symptomatic relief may be obtained by resting the elbow of the affected side on the arm of the chair, thereby elevating the shoulder. A sling may serve the same purpose. Specific strengthening and stretching exercises for the shoulder girdle muscles taught by a knowledgeable physical therapist can help (Fig. 4-10). Faulty posture and poor body mechanics should be corrected, and positions that aggravate the condition should be avoided. General health factors should be addressed as well, especially deconditioning and obesity. If symptoms are worsened by certain work activities, a minor alteration in the position of the arms while working could help.

Fig. 4-10 Shoulder exercises for thoracic outlet syndrome. A, Neck retraction. The head is pulled straight back, keeping the jaw level. The position is held for 5 to 10 seconds. B, Shoulder rolls are performed by shrugging up, back, and down in a circular motion. C, Corner stretch. With the hands at shoulder height, the patient stands and leans into a corner until a gentle stretch is felt. This is held for 5 to 10 seconds. D, To strengthen the serrati, the weight is pushed upward so that the shoulders are lifted off the table. E and F, The trapezius is strengthened by raising and drawing the shoulders backward to bring the scapulae upward and together.

For hyperabduction syndrome, avoidance of the hyperabducted position is usually the only treatment necessary. A gauze strip tied to the wrist and attached to the foot of the bed to prevent hyperabduction at night may be temporarily necessary for those patients whose symptoms occur primarily at night.

The rare case of acute vascular involvement is an emergency and requires prompt referral to a vascular surgeon. Otherwise, operative treatment is considered only when conservative measures fail to obtain significant relief after 4 to 6 months. Removal of the first dorsal and cervical ribs combined with release of any abnormal scalene muscle insertions is performed. These procedures are all combined with vascular repair when indicated.

NOTE: Thoracic outlet syndrome is probably quite uncommon, although its actual incidence is difficult to assess. Unfortunately, the diagnosis is often used in an attempt to assign a diagnosis to subjective symptoms that are difficult to correlate with known neuroanatomic pathways. In addition, the standard physical tests (Adson’s, etc.) are also of somewhat questionable value, and except for those rare cases of vascular involvement, there are no good special studies that can be used to confirm the diagnosis. The results of surgery performed for pain relief alone are also quite variable, and surgery is associated with a significant complication rate.

ERB–DUCHENNE PARALYSIS

This is the most common type of obstetric paralysis. Damage to the upper roots (C5 and C6) leads to paralysis of the deltoid muscle, the external rotators of the shoulder, the elbow flexors, and the supinators of the forearm. Residual weakness of these muscles leads to the characteristic “waiter’s-tip” position in which the arm is held adducted and internally rotated and the forearm is pronated (Fig. 4-11). Wrist and finger function are usually normal.

Fig. 4-11 The “waiter’s-tip” position. After partial upper arm paralysis, the upper extremity is frequently shortened and slightly smaller, and the palm often faces backward at rest.

WHOLE-ARM PARALYSIS

The limb is often completely flaccid and without motor function in this uncommon type of birth palsy. The hand tends to be dry and atrophic, and extensive sensory loss is often present.

KLUMPKE’S PARALYSIS

Klumpke’s paralysis is quite rare. In this condition, the lower cervical and first thoracic roots are involved. The finger and wrist flexors are denervated along with the intrinsic muscles. A clawhand deformity often results. Horner’s syndrome may also be present. Sensory loss involves the affected dermatomes of the lower plexus. The upper part of the arm is frequently uninvolved.