, Erb's point
or the punctum nervosum
is a site at the lateral root of the brachial plexus
located 2–3 cm above the clavicle
It is named for Wilhelm Heinrich Erb
. Taken together, there are six types of nerves that meet at this point.
Convergence of nerves
Erb's point is formed by the union of the C5
nerve roots, which later converge. At the nerve trunk, branches of suprascapular nerves
and the nerve to the subclavius
also merge. Afterwords, the merged nerve divides into the anterior
division of C5 and C6.
Injury to Erb's point is commonly sustained at birth or from a fall onto the shoulder
. The nerve roots normally involved are C5 and partly C6. Symptoms include paralysis of the biceps
, and coracobrachialis
(through the musculocutaneous nerve
); the brachioradialis
(through the radial nerve
); and the deltoid
(through the axillary nerve
). The effect is called "Erb's palsy
". Typically, an affected person's arm hangs at the side with the hand rotated medially, like a porter
waiting for a tip; hence the colloquial name "porter's tip hand".