This is a chronic degenerative disease of the mid-and lower cervical spine that narrows the spinal canal and intervertebral foramina, causing compressive injury of the spinal cord and roots. The problem of central disc protrusion, discussed above, often contributes as one component of the narrowing of the canal. Because the main effects of cervical spondylosis are on the cord, this process is discussed in detail in Chap. 42, but cervical spondylosis is also a common cause of neck and arm pain, as described earlier. If minor signs of spinal cord and root involvement are present, a collar to limit movement of the head and neck may halt the progression and lead to improvement. Decompressive laminectomy or anterior excision of single spondylotic spurs and fusion are reserved for instances of the disease with advancing neurologic symptoms or intractable pain as discussed in Chap. 42. As with lumbar stenosis, success is not assured with surgery but can help prevent further progression of symptoms.
A number of anatomic anomalies occur in the lateral cervical region. These may, under certain circumstances, compress the brachial plexus, the subclavian artery, and the subclavian vein, causing muscle weakness and wasting, pain, and vascular abnormalities in the hand and arm. The condition is undoubtedly diagnosed more often than is justified, and the term has been applied ambiguously to a number of conditions, some of which are almost certainly nonexistent, comparable to the pyriformis syndrome in the buttock.
The most frequent of the abnormalities that cause neural compression, encompassed by the term thoracic outlet syndrome, is an anomalous incomplete cervical rib, with a sharp fascial band passing from its tip to the first rib; a taut fibrous band passing from an elongated and down-curving transverse process of C7 to the first rib; less often, a complete cervical rib, which articulates with the first rib; and anomalies of the position and insertion of the anterior and medial scalene muscles. Thus, the sites of potential neurovascular compression extend all the way from the intervertebral foramina and superior mediastinum to the axilla. Depending on the postulated abnormality and mechanism of symptom production, the terms cervical rib, anterior scalene, costoclavicular, and neurovascular compression have been applied. In addition, a droopy shoulder syndrome has been identified that purportedly stretches the brachial plexus and gives rise to similar symptoms; a majority of the patients have been young women with asthenic body habitus.
Variations in regional anatomy could explain these several postulated mechanisms, but to this day there is not full agreement about the validity of anterior scalene and costoclavicular syndromes. An anomalous cervical rib, which arises from the seventh cervical vertebra and extends laterally between the anterior and medial scalene muscles and then under the brachial plexus and subclavian artery to attach to the first rib, obviously disturbs the anatomic relationships of these structures and may compress them (Fig. 10-7). However, as an estimated 1 percent of the population has cervical ribs, usually on both sides, and only about 10 percent of these persons have neurologic or vascular symptoms (almost always one-sided), other factors must be operative.
The anterior and middle scalene muscles, which flex and rotate the neck, are both inserted into the first rib so that the subclavian artery and vein and the brachial plexus must pass between them. Hence abnormalities of insertion and hypertrophy of these muscles were once thought to be causes of the syndrome but sectioning them (scalenectomy) has so rarely altered the symptoms that this mechanism is no longer given credence.