Anatomy Lesson 17-MSK Brachial Plexus and Pectoral Girdle

Spinal Levels of Brachial Plexus

C5-T1

What is the interscalene triangle?

• The anterior and middle scalene muscles attach to the first rib to form the interscalene triangle

• This triangle is where the brachial plexus passes through

What are some complications that can arise in the interscalene triangle (3)?

-Scalene Hypertrophy

-Supernumerary Rib

-Subclavian Artery Compression

Scalene Hypertrophy

• If the anterior and/or middle scalene muscles get too large (due to respiratory issues or steroids), they can impinge the upper roots of the brachial plexus leading to loss of motor movement in the proximal limb structures

Supernumerary Rib

An extra rib above the first rib. This causes the floor of the interscalene triangle to rise which leads to impingement of lower roots of the brachial plexus leading to loss of motor movement in distal limb structures

Subclavian Artery Compression

Can be caused by a supernumerary rib or hyperabduction syndrome. It can cause motor and sensory loss to the arm

Damage to upper roots vs lower roots vs vascular issue

• Upper Roots: Motor loss to proximal areas

• Lower Roots: Motor loss to distal areas

• Vascular Issue: Motor and sensory loss to whole arm

Saturday Night Palsy

Compression of the radial nerve leading to wrist drop. Sensory loss in the radial section

Hyperabduction Syndrome

When your arm is hyperabducted, the head of the humerus compresses the brachial plexus and axillary artery and vein. This causes temporary motor and sensory loss

Erbs Palsy

• Damage to the upper roots of the brachial plexus. Can be a result of improper childbirth in which a child’s head is pulled as their shoulders come out leading to brachial plexus damage. Leads to proximal motor issues

Klumpke’s Palsy

Damage to the lower roots of the brachial plexus. Can be a result of hyperabduction of the arm. Leads to distal motor issues