PCL 5 - Median and Ulnar Nerves

Median Nerve

Origin:

- lateral cord of brachial plexus (C6, C7)

- Medial cord (C8, T1)

Course:

- becomes superficial proximal to wrist

- passes deep to flexor retinaculum (transverse carpal ligament) as it passes through carpal tunnel to hand

Distribution:

- thenar muscles (except adductor pollicis and deep head of flexor pollicis brevis)

- lateral lumbricals (2^nd and 3^rd digits)

- provide sensation to skin of palmar and distal dorsal aspects of lateral(radial) 3 ½ digits and adjacent palm

Recurrent (thenar) branch

Origin:

- Arises from median nerve as soon as it has passed distal to flexor retinaculum

Course:

- loops around distal border of flexor retinaculum

- enters thenar muscles

Distribution:

- abductor pollicis brevis

- opponens pollicis

- superficial head of flexor pollicis brevis

Lateral branch

Origin:

- Lateral division of median nerve as it enters palm of hand

Course:

- runs laterally to palmar thumb

- radial side of 2^nd digit

Distribution:

- 1^st lumbrical

- skin of palmar and distal dorsal aspects of thumb and radial half of 2^nd digit

Medial branch

Origin:

- medial division of median nerve as it enters palm of hand

Course:

- runs medially to adjacent sides of 2^nd – 4^th digits

Distribution:

- 2^nd lumbrical

- skin of palmar and distal dorsal aspects of adjacent sides of 2^nd – 4^th digits

Palmar cutaneous branch

Origin:

- arises from median nerve just proximal to flexor retinaculum

Course:

- Passes between tendons of palmaris longus and flexor carpi radialis

- Runs superficial to flexor retinaculum

Distribution:

- skin of central palm

Ulnar Nerve

Origin:

- Terminal branch of medial cord (C8, T1; often also receives C7 fibres)

Course:

- becomes superficial in distal forearm, passing superficial to flexor retinaculum (transverse carpal ligament) to enter hand

Distribution:

- majority of intrinsic muscles of hand (hypothenar, interosseous, adductor pollicis, deep head of flexor pollicis brevis, medial lumbricals [for 4^th and 5^th digits])

- provides sensation to skin of palmar and distal dorsal aspects of medial (ulnar) 1 ½ digits & adjacent palm

Palmar cutaneous branch

Origin:

- arises from ulnar nerve near middle of forearm

Course:

- descends on ulnar artery and perforates deep fascia in the distal third of forearm

Distribution:

- skin at base of medial palm, overlying the medial carpals

Dorsal branch

Origin:

- Arises from ulnar nerve about 5cm proximal to flexor retinaculum

Course:

- Passes distally deep to flexor carpi ulnaris, then dorsally to perforate deep fascia and course along medial side of dorsum of hand, dividing into 2 to 3 dorsal digital nerves

Distribution:

- skin of medial aspect of dorsum of hand and proximal portions of little and medial half of ring finger (occasionally also adjacent sides of proximal portions of ring and middle fingers)

Superficial branch

Origin:

- arises from ulnar nerve at wrist as they pass between pisiform and hamate bones

Course:

- passes palmaris brevis and divides into 2 common palmar digital nerves

Distribution:

- palmaris brevis

- sensation to skin of the palmar and distal dorsal aspects of digit 5 and of the medial (ulnar) side of digit 4 and proximal portion of palm

Deep branch

Origin:

- arises from ulnar nerve at wrist as they pass between pisiform and hamate bones

Course:

- passes between muscles of hypothenar eminence to pass deeply across palm with deep palmar (arterial) arch

Distribution:

- hypothenar muscles (abductor, flexor, and opponens digit minimi)

- lumbrical of digit 4 and 5

- all interossei

- adductor pollicis

- deep head of flexor pollicis brevis