In endeavoring to localize transverse lesions of the cord, such as result from traumatism, tumors, etc., one must bear in mind that the spinal nerves originate from segments in the cord some distance above where they make their exit from the spinal foramina. Chipault (quoted by Starr) gives the following practical rule: "In the cervical region add one to the number of the vertebra, and this will give the segment opposite to it. In the upper dorsal region add two: from the sixth to the eleventh dorsal vertebra add three. The lower part of the eleventh dorsal spinous process and the space below it are opposite the lower three lumbar segments. The twelfth dorsal spinous process and the space below it are opposite the sacral segments." The spinal cord ends at the lower part of the first lumbar vertebra.

Fig. 486.   Diagram of distribution of cutaneous nerves, based on figures of Hasse and of Cunningham. On right side, areas supplied by indicated nerves are shown; on left side, points at which nerves pierce the deep fascia. V1, V2, V3, divisions of fifth cranial nerve; GA, great auricular; GO, SO, greater and smaller occipital; SC, superficial cervical; St, CI, Ac, sternal, clavicular, and acromial branches of supraclavicular (Sc/); Ci, circumflex: MS, musculospiral; IH, intercostohumeral; LIC, IC, lesser internal and internal cutaneous; EC, external cutaneous; IH, iliohypogastric; II, ilio inguinal; T12. last thoracic; GC, genitocrural; EC, external cutaneous; ML , middle cutaneous; IC internal cutaneous; P, pudic; SS, small sciatic; 0, obturator; C, T, L, and S, cervical, thoracic, lumbar, and spinal nerves. (Piersol).

Fig. 486. - Diagram of distribution of cutaneous nerves, based on figures of Hasse and of Cunningham. On right side, areas supplied by indicated nerves are shown; on left side, points at which nerves pierce the deep fascia. V1, V2, V3, divisions of fifth cranial nerve; GA, great auricular; GO, SO, greater and smaller occipital; SC, superficial cervical; St, CI, Ac, sternal, clavicular, and acromial branches of supraclavicular (Sc/); Ci, circumflex: MS, musculospiral; IH, intercostohumeral; LIC, IC, lesser internal and internal cutaneous; EC, external cutaneous; IH, iliohypogastric; II, ilio-inguinal; T12. last thoracic; GC, genitocrural; EC, external cutaneous; ML , middle cutaneous; IC internal cutaneous; P, pudic; SS, small sciatic; 0, obturator; C, T, L, and S, cervical, thoracic, lumbar, and spinal nerves. (Piersol).

The areas of cutaneous sensibility aid in determining the seat of the lesion. The nerves supplying these various areas are shown in Fig. 486.

Lesions above the fourth cervical nerve are very speedily fatal. The muscular paralyses, as guides to the seat of the lesion in the cervical region, are given by Thorburn as follows:

supraspinatus and infraspinatus...

Fourth cervical nerve.

Teres minor (?).........

Biceps..........

Fifth cervical nerve.

Brachialis anticus..........

Deltoid........

Supinator longus......

Supinator brevis (?)

Subscapularis........

Sixth cervical nerve.

Pronators.......

Teres major.......

Latissimus dorsi....

Pectoralis major.....

Triceps.......

Serratus magnus......

Extensors of the wrist.....

Seventh cervical nerve

Flexors the wrist......

Eighth cervical nerve.

Interossei..........

First dorsal nerve.

Other intrinsic muscles of the hand...

In fractures of the dorsal region Thorburn has shown that the lesion is usually two vertebrae higher than the nerve coming out from below the displaced vertebra. They cause paralysis of the abdominal muscles, legs, bladder, and rectum.

According to Starr, fractures in the region of the last two dorsal vertebrae cause anaesthesia up to Poupart's ligament, and if the patient recovers the thighs remain paralyzed. In fractures of the upper part of the lumbar region the paralysis may be limited to the legs below the knees but involves the bladder and rectum. Recovery leaves the patient with some power of getting about on crutches with the aid of apparatus to keep the ankles and knees firm, as the thighs are under voluntary control.

Lesions below the first lumbar, those of the cauda equina, give paralysis of the feet and peronei, loss of control of the bladder and rectum, and anaesthesia in the saddle-shaped area on the buttocks, about the anus, and on the posterior part of the genitals.

The diagnosis between lesions of the cauda equina and lower portion of the cord is not always possible. The prognosis of lesions of the cauda equina is, of course, much better than when the cord itself has been injured.