Cervical Plexus

CERVICAL PLEXUS (plexus cervicalis) is formed by a loop-like connection between the anterior branches of the first four cervical nerves C1-C4 (fig. 1). These connections are called ansae cervicales, three of which are present in the plexus itself - ansa cervicalis prima, s. atlantis, secunda, tertia; the fourth loop is not constant, it connects the plexus cervicalis with the plexus brachialis. The plexus cervicalis lies on the corresponding cervical vertebrae and on the muscles attached to the posterior tubercles of the transverse processes; it is covered by m. sternocleidomastoideus.

In addition to the brachial plexus, the cervical plexus connects: 1) C1 with the hypoglossus nerve, forming ansa hypoglossi, s. ansa cervicalis profunda; 2) C1 with the accessory nerve; 3) with the cervical ganglion sup. and with the sympathetic trunk. The cervical plexus gives off cutaneous and muscular branches. From the individual cervical nerves before the formation of the plexus, muscular branches emerge to mm. recti capitis ant. and lat., longus colli, longus capitis, intertransversarii, scalenus ant. and med., levator scapulae.

Figure 1. Formation of the cervical plexus and nerves arising from it: I-II-III-IV-V-VI nn. spinales cervicales: 1-n. for m. rectus capitis; 2 and 3-n. for m. long. capitis; 4-n. for m. intertransv.; 5-n. for m. long. capit. et colli; 6-n. for m. intertransv.; 7-n. for m. levator scapulae; 8-n. for m. long. colli; 9-n. for m. intertransv.; 10-n. for m. scalen. medius; 11-n. for m. long. colli; 12-n. for m. scalen. ant.; 13-n. for m. scalen. medius; 14-n. for m. rhomboideus; 15, 16-n. for m. levator scapulae; 17-nn. from m. trapezius to mm. supraclaviculares; 18-n. for m. trapezius; 19-ansa hypoglossi; 20-n. for m. trapezius; 21-n. cutaneus colli; 22-n. auricularis magnus; 23-ram. descendens n. hypoglossi; 24-n. occipitalis minor; 25-n. for m. rectus capitis; 26-n. hypoglossus.

From C3-C4-n. phrenicus (see Phrenicus nervus). From the cutaneous branches of the cervical plexus are known: n. occipitalis minor, n. auricularis magnus, n. cutaneus colli and n. supraclavicularis. N. occipitalis minor originates from ansa secunda and appears externally on the posterior edge of m. sternocleidomastoidei (fig. 2), then ascends upward and ends in the occipital region. N. auricularis magnus arises from C3, like the previous nerve, emerges externally at the posterior edge of m. sternocleidomastoidei, where it divides into 2 branches-anterior et posterior-and innervates the skin of the auricle and regio parotidomasseterica. N. cutaneus colli originates from C3; emerging at the posterior edge of m. sternocleidomastoidei, it curves around it and on the external surface proceeds toward the hyoid bone, dividing into branches: ramus sup. innervates the skin of regionis suprahyoideae, where it anastomoses with n. facialis, ramus inf. supplies the skin of regionis infrahyoideae. N. supraclavicularis arises from C4, upon external appearance it consists of several branches, which divide into nn. supraclaviculares anteriores, medii et posteriores and proceed forward, backward, and to the side, supplying the nerves to the skin of the neck, shoulder, and upper parts of the thoracic region (see Nerves).

Thus, the cervical plexus supplies: with sensory fibers the skin behind the ear, the skin of the auricle, occiput, neck, and shoulder; with motor fibers: a) short deep occipital muscles, of which two-mm. rectus capitis post. major et minor-pull the head back, two muscles-mm. obliquus capitis sup. et inf.-turn the head to the side and m. rectus capitis lat. tilt the head to the side; b) posterior muscles of the neck, of which three-mm. longus colli, longus capitis, rectus capitis ant.-tilt the head forward, mm. scaleni ant., medius, post. (these three muscles receive innervation simultaneously from the plexus brachialis) flex the cervical part of the spine; moreover, the cervical plexus competes with n. accessorius in the innervation of the muscles sternocleidomastoideus, trapezius, levator scapulae. The most important nerve of the cervical plexus is n. phrenicus, which goes to the diaphragm.

Figure 2. Cutaneous branches of the cervical plexus: 1-n. occipitalis; 2-n. auricularis post.; 3-n. auricularis post.; 4-glandula parotis; 5-rami n. facialis; 6-ram. colli n. facialis; 7-n. cutaneus colli; 8-v. jugularis ext.; 9-platysma; 10-m. omohyoideus; 11-nn. supraclaviculares ant.; 12-nn. supraclaviculares medii; 13-nn. supraclaviculares post.; 14-rami musculares for m. trapezius; 15-nn. supraclaviculares; 16-m. trapezius; 17-m. scalenus medius; 18-n. accessorius (ramus externus); 19-m. sternocleidomastoideus; 20-m. levator scapulae; 21-m. splenius capitis; 22-n. auricularis magnus; 23-n. occipitalis tertius; 24-n. occipitalis minor; 25-n. auricularis magnus; 26-n. occipitalis magnus.

Pathology of the cervical plexus. Lesions of the cervical plexus can be unilateral or bilateral; the latter form is more frequently observed and manifests as paralysis of the cervical muscles or their cramps, depending on the process, and neuralgia. In paralysis, the cervical muscles do not function-the patient's head powerfully tilts forward so strongly that the chin touches the sternum (fig. 3); the patient cannot lift the head upward. Paralysis of n. phrenicus leads to paralysis of the diaphragm. Cramps most often spread to mm. obliquus capitis, splenius and diaphragm. In unilateral clinical cramps, m. obliqui capitis inf. the head constantly turns to the affected side; in bilateral cramps the head turns in both directions-rotatory cramps of the head, s. tic rotatoire. In tonic cramps, the head freezes for some time in the turned position. In unilateral cramps of m. splenii, the head is tilted back and to the affected side. In the diaphragm, clonic cramps are more often observed, manifesting as hiccups.

Neuralgia is localized mainly in the area of nn. occipitalis major et minor (fig. 3). Position of the head in case of cervical plexus lesion. Neuralgia of n. auricularis magnus-neuralgia occipitalis, s. cervico-occipitalis. In neuralgias, pain is localized along the course of these nerves; objectively there is painful hyperesthesia, soreness on pressure on the plexus above the clavicle-supraclavicular point, syn. Erb's point. The cervical plexus can be affected in general infections, intoxications, but most often it suffers in processes in the surrounding tissues in the neck or in diseases of the upper cervical spine.

Treatment-depending on the etiological factor, as well as symptomatic: in paralysis-physiotherapy, in neuralgias-diathermy, counter-irritants.

E. Kononova.