Arm and Neck Pain

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Chapter 29 Arm and Neck Pain

Evaluation of the patient with arm and/or neck pain is based on a careful history and clinical examination. Diagnosis of the common causes and a treatment plan can almost always be accomplished in the office before laboratory investigation, but further study may be required if the patient fails to improve or has other specific indications for imaging or electrical studies.

A useful approach is to consider the diagnosis in terms of pain-sensitive structures in the neck and upper limbs. These structures may be part of the nervous system or may involve joints. Neurological causes should be considered in terms of the innervation of the neck and arm, and non-neurological causes are based on dysfunction of the other anatomical structures of the arm or neck. Because nerve root irritation generates neck muscle spasm, this type of pain is usually lumped into the “neurological” category. Some essentially non-neurological conditions have neurological complications and are grouped in this chapter as “in-between” disorders.

Clinical Assessment

History

Neurological Causes of Pain

Plexus Pain

Peripheral pathology may involve the brachial plexus (Fig. 29.1) or individual nerves extending to the hand. Infiltrative or inflammatory lesions of the brachial plexus produce severe brachialgia radiating down the upper limb and also spreading to the shoulder region. Radiation to the ulnar two fingers suggests that the origin is in the lower brachial plexus, and radiation to the upper arm, forearm, and thumb suggests an upper plexopathy. Patients with a thoracic outlet syndrome complain of brachialgia and numbness or tingling in the upper limb or hand when working with objects above the head.

image

Fig. 29.1 Brachial plexus: schema.

(Netter illustration from www.netterimages.com © Elsevier Inc. All rights reserved.)

Examination

The physical examination is designed to localize a neurological deficit related to spinal cord, nerve roots, or peripheral nerves. Evaluation for non-neurological pathology is required because rheumatological problems often complicate a primarily neurological problem. A detailed knowledge of motor and sensory neuroanatomy is required for accurate localization.

Motor Signs

The examination begins with inspection. Particular attention is paid to atrophy of muscles of the shoulders, arms, and the small muscles of the hands. Fasciculations are often due to anterior horn cell disease, but they may be part of the neurology of cervical spondylosis and radiculopathy. Significant sensory signs would argue against anterior horn cell degeneration.

Muscles in the various myotomes must be tested individually. When there is unilateral weakness, the contralateral side can act as a control, but some standard measure of strength is necessary for accurate evaluation when bilateral weakness is present. If one can overcome the action of a patient’s muscle by resisting or opposing its action close to the joint it moves, using an equivalent equipotent muscle of the examiner (fingers test fingers, whole arm tests biceps), then that muscle in the patient is, by definition, weak. The degree of weakness can be graded, and the 5-point (Medical Research Council [MRC]) grading scale is often used. Grade 5 represents normal strength. Grade 4 represents “weakness” somewhere between normal strength and the ability to move the limb only against gravity (grade 3). Grade 4 covers such a wide range of weakness that it is usually expanded. One simple expansion is into “mild, moderate, or severe.” When the muscle can move the joint with the effect of gravity eliminated, it is graded at 2, and grade 1 is just a flicker of contraction.

The lower limbs must always be examined, even when the patient complains of symptoms only in the upper limbs. Evidence of a myelopathy as evidenced by the finding of sensory or motor dysfunction in the lower limbs, when combined with the presence of radicular signs in the upper limbs, indicates a spinal cord lesion in the neck.

The distribution of weakness is all important in localizing the problem to nerve root, plexus, peripheral nerve, muscle, or even upper motor neuron (central weakness). It is useful to use a simplified schema of radicular anatomical localization when evaluating nerve root weakness because overlap of segmental innervation of muscles can complicate the analysis (Table 29.1).

Table 29.1 Segmental Innervation Scheme for Anatomical Localization of Nerve Root Lesions

Segment Level Muscle(s) Action
C4 Supraspinatus First 10 degrees of shoulder abduction
C5 Deltoid Shoulder abduction
  Biceps/brachialis/brachioradialis Elbow flexion
C6 Extensor carpi radialis longus Radial wrist extension
C7 Triceps Elbow extension
C7 Extensor digitorum Finger extension
C8 Flexor digitorum Finger flexion
T1 Interossei Finger abduction and adduction
  Abductor digiti minimi Little finger abduction

The thoracic outlet syndrome, or brachial plexus entrapment, is an overdiagnosed condition. Maneuvers designed to test for compromise of the neurovascular structures passing through the thoracic outlet are often difficult to interpret. In these maneuvers, the arm is extended at the elbow, abducted at the shoulder, and then rotated posteriorly. The examiner palpates the radial pulse while listening with a stethoscope over the brachial plexus in the supraclavicular fossa. The patient takes a deep inspiration and turns the head to one or the other side. Many normal individuals lose their radial pulse, but the emergence of a bruit does suggest at the least vascular entrapment (Adson test). The patient then exercises the hands held above the head with extended elbows—numbness, pain, or paresthesias, often with pallor of the hand, support the diagnosis (Roos test).

A distribution of weakness that does not conform to a clearly defined anatomical distribution of a single peripheral nerve in the upper limb suggests plexopathy. Upper plexus lesions cause mainly shoulder abduction weakness, and lower plexus lesions will affect the small muscles of the hand.

Pathology and Clinical Syndromes

Spinal Cord Syndromes