Erb's point

In neurology, Erb's point or punctum nervosum is a site at the lateral root of the brachial plexus, located 2-3 centimeters above the clavicle.

In cardiology, Erb's point refers to the third intercostal space on the left sternal border where S2 is best auscultated.

Convergence of nerves
Erb's point is formed by the union of the C5 and C6 nerve roots, which later converge.

At the nerve trunk, branches of suprascapular nerves and nerve to subclavius also merge. Afterwards,the merged nerve divides into anterior and posterior division of C5 & C6.

Erb's point is the site after the converged trunk of C5 & C6 divides into suprascapular nerve and subclavius branches and before the anterior and posterior division.

Taken together, there are 6 types of nerves that meet at this point.

Clinical significance
Injury to this point is commonly sustained at birth or via a fall onto the shoulder. The nerve roots normally involved is C5 and partly C6. Injury to this area causes paralysis of biceps, deltoid, brachialis, brachioradialis, and coracobrachialis - which is supplied by the axillary nerve (deltoid), musculocutaneous nerve (biceps, brachialis and coracobrachialis) and radial nerve (brachioradialis). This causes the arm to hang at the side with the hand rotated medially- like a porter waiting for a tip, thus the nick names "police man's tip", "porter's tip hand". This injury is also called "Erb-Duchenne palsy" or Erb's Palsy.

Eponym
It is named for Wilhelm Heinrich Erb.