J. Anat. (1994) 185, pp. 439-442, with 3 figures Printed in Great Britain 439 Short Report

The cutaneous branch of the human suprascapular

M. L. AJMANI Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India

(Accepted 5 April 1994)

ABSTRACT The cutaneous branch of the suprascapular nerve was studied bilaterally in 34 adult cadavers. In 5 the suprascapular nerve derived its fibres from the ventral rami of the 4th, 5th and 6th cervical . The cutaneous branch was observed in 14.7 % of the 68 limbs examined. In 3 cadavers the cutaneous branch arose from the upper branch to the supraspinatus muscle and in 1 case from the stem of the suprascapular nerve just above the transverse scapular ligament. In 1 case the cutaneous branch arose deep to the transverse scapular ligament. The cutaneous branch was present bilaterally in 3 and unilaterally in 2 cadavers. Every suprascapular nerve with a cutaneous branch had a normal course. After passing deep to the acromioclavicular ligament, the cutaneous branch bent forward near the tip of the process and pierced the close to its origin and came to lie deep to the deep fascia. In the subcutaneous tissue, it divided into 3-4 twigs and supplied the proximal third of the lateral aspect of the arm within the territory of the axillary nerve. Presumably in normal human arms the cutaneous component of the suprascapular nerve is contained within the axillary nerve.

closely and firmly to the under surface of the deltoid. INTRODUCTION It was therefore decided to establish the normal range The sensory nerve supply of the skin over the tip of of variation in distribution of the suprascapular nerve the and the lateral aspect of the arm is in an Indian population. variable. The area is normally supplied by the lateral supraclavicular nerves and the upper lateral cutaneous nerve of the arm (Fig. 1). Of the current texts MATERIAL consulted, none mentioned a cutaneous branch from The observations were made on both upper limbs the suprascapular nerve in man. Yamada (1968) from 30 male and 4 female cadavers available in the described such a branch in Japanese and named it the Department of Anatomy, All India Institute of 'Nervus cutaneus subacromialis'. Later Horiguchi Medical Sciences, New Delhi over a period of 6 y, (1980) also found a cutaneous offshoot from a ranging in age from 18 to 55 y. The origin, course and suprascapular nerve in a Japanese cadaver. A cu- branches of the suprascapular nerve were examined taneous branch of the suprascapular nerve is well by dissection in the paravertebral, scapular and recognised in lower primates (Bolk, 1902). It is shoulder region. possible that the occurrence of a cutaneous branch of the suprascapular nerve has been neglected in man OBSERVATIONS because (1) the nerve is likely to be damaged when the deltoid is divided near its origin in the course of In most of the cadavers (25), the ventral rami of the routine dissection; (2) the cutaneous branches of the 5th and 6th cervical nerves joined to form the upper axillary nerve pierce the deltoid at variable points and trunk of the brachial plexus. In 5 cadavers, the could be confused with the nerve in question; and (3) suprascapular nerve derived its fibres from the ventral the difficulty in dissecting the nerve as it adheres rami of the 4th, 5th and 6th cervical nerves and

Correspondence to Dr M. L. Ajmani, Department of Anatomy, All India Institute of Medical Sciences, New Delhi- 110029, India. 440 M. L. Ajmani

plexus did not receive fibres from the ventral ramus of the 4th cervical nerve; the suprascapular nerve emerged from the lateral aspect of the upper trunk near its bifurcation. In 2 cadavers the suprascapular nerve arose from the lateral aspect of the upper trunk formed by the union of the 5th and 6th cervical nerves but the plexus was of postfixed type. After arising from the upper trunk of the brachial plexus the suprascapular nerve pursued a normal course in all cases. Having entered the supraspinous fossa, as normally it supplied upper and lower branches to the supraspinatus muscle and filaments to the capsule of the acromioclavicular and shoulder joints; it then descended through the spinoglenoid notch, under cover of a loose fascial band that stretches across it, to end in the infraspinatus muscle. The cutaneous nerve in question was seen only in male cadavers, but there were only 4 females in the Anterior Posterior sample, and was encountered in 14.7 % of the 68 limbs examined. In 8.8 % of limbs, it received fibres from Fig. 1. Anterior and posterior views of the upper limb. SCN, ventral rami of the 5th and 6th cervical nerves whereas supraclavicular nerve; CSSN, cutaneous branch of suprascapular nerve; IBN, intercostobrachial nerve; PCNA, posterior cutaneous in 5.9 %, in addition to these nerves, it also received a nerve of arm; LLCA, lower lateral cutaneous nerve of arm; PCNF, contribution from the ventral ramus of the 4th cervical posterior cutaneous nerve of forearm; LCNF, lateral cutaneous nerve. In 6 limbs the cutaneous branch arose from the nerve of forearm; MCNF, medial cutaneous nerve of forearm. upper branch to the supraspinatus muscle and in 2 limbs from the stem of the suprascapular nerve 3 mm emerged from the lateral aspect of the upper trunk. above the transverse scapular ligament (Fig. 2). In 2 This was classified as a prefixed type of brachial limbs the cutaneous branch arose deep to the plexus. In 2 cadavers, the upper trunk of the brachial transverse scapular ligament (Fig. 3). Whatever the

Fig. 2. Origin of the cutaneous branch (CSSN) from the upper branch (UB) of the suprascapular nerve (SSN). LB, lower branch of suprascapular nerve; TSL, transverse scapular ligament; SS, supraspinatus muscle. Human suprascapular nerve 441

Fig. 3. Origin of the cutaneous branch (CSSN) from the main trunk of the suprascapular nerve (SSN) deep to the transverse scapular ligament (TSL). UB, upper branch of suprascapular nerve; UT, upper trunk; SS, supraspinatus muscle; D, deltoid muscle. source oforigin, the cutaneous branch turned upwards border of the deltoid, continuing as the upper lateral and laterally along the upper part ofthe supraspinatus cutaneous nerve of the arm and supplying the skin muscle. It then passed deep to the acromioclavicular over the lower part of the deltoid muscle. The area of ligament where it gave a filament to the acromiocla- distribution of the cutaneous branch of the supra- vicular joint. In its further course, it tended to bend scapular nerve appears to be the lateral aspect of the forward near the tip of the acromion process and proximal third of the arm close to and encroaching pierced the deltoid muscle close to its origin from the the area supplied by the upper lateral cutaneous nerve tip of the acromion. The cutaneous branch of the of the arm. suprascapular nerve was present bilaterally in 3 and unilaterally in 2 cadavers. The peripheral distribution of the cutaneous branch DISCUSSION of the suprascapular nerve was dissected out bi- The diagnosis of the site of a nerve injury depends laterally in 3 cadavers. Near the acromion process, it on knowing the distribution of the individual cu- pierced the deltoid muscle and came to lie deep to the taneous nerves and their approximate site of origin deep fascia. In the subcutaneous tissue, it divided into from the main nerves, although the nerve fibres may 3-4 twigs and supplied the lateral aspect of the sometimes pass to their destinations by unusual routes proximal third of the arm. In all 3 cases, the most and hence modify the expected clinical effects of anterior filament communicated with a branch of the destruction of a particular nerve. Normally the lateral supraclavicular nerve. The main trunk of the brachial plexus and each of its branches contains cutaneous nerve descended in the subcutaneous tissue nerve fibres from more than one ventral ramus. Thus on the upper part of the lateral aspect of the middle the area of skin which loses sensation as a result of third of the arm. destruction of a ventral ramus is not the same as that The area supplied by the cutaneous branch of the which results from destruction of a branch of the suprascapular nerve was bounded proximally by the plexus (Romanes, 1984). Also, it should be appreci- lateral supraclavicular nerves, distally by the lower ated that cutaneous nerves supplying adjacent areas lateral cutaneous nerve of the arm, anteromedially by of skin share a considerable area by the overlapping of the medial cutaneous nerve of the forearm, and their fine terminal branches which sometimes cannot posteriorly by the upper lateral cutaneous nerve of the be followed by dissection. arm. Normally the posterior branch of the axillary In the present study the suprascapular nerve arose nerve pierces the deep fascia low on the posterior from the upper trunk of the brachial plexus as normal 29 ANA 185 442 M. L. Ajmani

Table Details of subjects with cutaneous branches of suprascapular nerve

Percentage of Total no. Sex Side Nerve fibres involved upper limbs No. of of upper Age with a cutaneous cases limbs Male Female (y) Right Left C 4,5 C 4,5,6 C 5,6 branch

Horiguchi 5 6 4 1 57-90 3 3 1 3 1 (1980) Present 5 10 5 18-55 5 5 4 6 14.7 study near the confluence of the ventral rami of the 5th and (Bolk, 1902), except that in monkeys the cutaneous 6th cervical nerves except in 5 cadavers in which it also branch winds around the anterior border of the received a contribution from the 4th cervical nerve. deltoid to become subcutaneous. The branches of the All the cases studied by Murakami et al. (1977) plexus supplying adjacent areas of skin overlap with showed that the suprascapular nerve arose from a each other. Thus the distribution of the cutaneous normal brachial plexus near the confluence of the branch of the suprascapular nerve to the skin ventral rami of the 5th and 6th cervical nerves. In 4 of coincides with that of the axillary nerve in the arm. the cases studied by Horiguchi (1980) the supra- Bolk (1902) observed that in prosiminians and New scapular nerve derived fibres from the ventral rami of World monkeys, the relevant skin area was supplied the 4th, 5th and 6th cervical nerves (see Table). by the suprascapular nerve, but in Old World The cutaneous branch was seen in 14.7 % of upper monkeys it was supplied by the axillary nerve. He limbs. The presence of this branch of the supra- ascribed it to the shift of the sensory fibres from the scapular nerve had no relation to variations in the 'prozonal' suprascapular nerve to the closely related brachial plexus. The cutaneous branch was observed 'metazonal' axillary nerve. Probably in normal in 2 cases (4 upper limbs) with a prefixed type of human arms the cutaneous component of the supra- brachial plexus and in 3 cases (6 upper limbs) with a scapular nerve is contained within the axillary nerve. normal brachial plexus. Similar findings were reported in Japanese subjects by Horiguchi (1980). The cu- REFERENCES taneous branch of the suprascapular nerve was found BOLK L (1902) Der Plexus cervico-brachialis der Primaten. Petrus bilaterally in 3 and unilaterally in 4 Japanese cadavers Camper 1, 371-567. (Murakami et al. 1977; Horiguchi, 1980) and bi- HORIGUCHI M (1980) The cutaneous branch of some human in in suprascapular nerves. Journal of Anatomy 130, 191-195. laterally in 3 and unilaterally 2 cadavers the MURAKAMI T, OHTANI 0, OUTI H (1977) Suprascapular nerve with present material (Table). cutaneous branch to the upper arm. Acta Anatomica Nipponica The course of the cutaneous branch of the supra- 52, 95. scapular nerve from its origin to the deltoid muscle ROMANES GJ (1984) Cunningham's Manual of Practical Anatomy, 14th edn, p. 36. New York: Oxford University Press. has been found to be similar in all cadavers (Mura- YAMADA M (1968) Manual of Anatomical Dissection, Kinazawa kami et al. 1977) and in prosimians and monkeys University School of Medicine (in Japanese).