Posterior triangle of the neck

The posterior triangle (or lateral cervical region) is a region of the neck.

Boundaries
It has the following boundaries:
 * in front, by the Sternocleidomastoideus
 * behind, by the anterior margin of the Trapezius
 * its base is formed by the middle third of the clavicle
 * its apex, by the occipital bone

Occipital and subclavian triangles
The posterior triangle is crossed, about 2.5 cm above the clavicle, by the inferior belly of the Omohyoideus, which divides the space into two triangles:


 * an upper or occipital triangle
 * a lower or subclavian triangle

Contents
It contains the accessory nerve, which crosses the triangle from the upper 1/3 of sternocleidomastoideus to the lower 2/3 of the trapezius.

Clinical significance
It is particularly vulnerable to damage at lymph node biopsy, where damage results in an inability to shrug the shoulders or raise the arm above the head (eg, for brushing hair)