The suprascapular nerve arises from the upper trunk of the brachial plexus which is formed by the union of the ventral rami of the cervical nerves C5-C6.

[1] After branching from the upper trunk, the nerve passes across the posterior triangle of the neck parallel to the inferior belly of the omohyoid muscle and deep to the trapezius muscle.

It then runs along the superior border of the scapula through the suprascapular canal,[1] in which it enters via the suprascapular notch inferior to the superior transverse scapular ligament and enters the supraspinous fossa.

[2] It then passes beneath the supraspinatus and curves around the lateral border of the spine of the scapula through spinogleniod notch to the infraspinous fossa.

This article incorporates text in the public domain from page 932 of the 20th edition of Gray's Anatomy (1918)