The Upper Extremity & Lower Extremity Nerves

Axillary Nerve

• branch of posterior cord of brachial plexus

• nerve roots: C5-6

• motor supply: teres minor, deltoid

• axillary nerve becomes upper lateral cutaneous nerve of arm and supplies the skin covering the lower half of deltoid and upper part of long head of triceps

Causes of Injury of Axillary Nerve

Axillary nerve can be injured due to:

- Dislocation of shoulder

- Fracture of surgical neck of humerus

• Effects:

- "Square shoulder” from deltoid muscle atrophy

- Sensory loss over lower half of deltoid

Radial Nerve

• Branch of posterior cord of brachial plexus

• Nerve Roots: C5-8, T1

• Exits axilla via triangular Interval, travels down humerus in radial groove.

• At the elbow, the radial nerve pierces the lateral muscular septum anterior to the lateral epicondyle and passes under the origin of the extensor carpi radialis brevis; it then divides into a superficial and a deep branch.

Radial Nerve – Motor supply (4 major muscles)

• Triceps - Elbow extension

• Anconeus - Weak elbow extensor

• Brachioradialis - Elbow flexion

• Supinator - Supination of forearm

Radial Nerve – Motor supply Continued (9 minor muscles)

• Extensor Carpi Radialis Longus - Action: Wrist extension, radial deviation

• Extensor Carpi Radialis Brevis - Action: Wrist extension, radial deviation

• Extensor Carpi Ulnaris - Action: Wrist extension, ulnar deviation

• Extensor Digitorum - Action: 2-5th digits extension at MCP, IP,

Wrist

• Extensor Digiti Minimi - Action: 5th digit extension at MCP, IP

• Extensor Pollicis Longus - Action: 1st digit extension at CMC, IP

• Extensor Pollicis Brevis - Action: 1st digit extension at MCP, IP

• Extensor Indicis - Action: 2nd digit extension, wrist extension

• Abductor Pollicis Longus - Action: 1st digit abduction and

extension at CMC joint

Radial Nerve – Sensory supply (4 nerves/branches)

• Lower Lateral Cutaneous Nerve of the Arm - Skin of lower half of lateral side of arm

• Posterior Cutaneous Nerve of the Arm - Skin of back of the arm

• Posterior Cutaneous Nerve of the Forearm - Skin of back of forearm

• Superficial Branch - Skin of lateral half of dorsum of hand, lateral two and half digits including thumb

Radial Nerve Injury

• Radial nerve can be injured in axilla, musculospiral groove, around radial neck

• Radial Tunnel Syndrome: tenderness in the extensor muscle mass of the forearm (distal to lateral epicondyle),

long finger extension test reproduces pain

• Posterior interosseous nerve syndrome

• Wrist drop

Ulnar Nerve

• Branch of medial cord of brachial plexus

• Nerve Roots: C7-T1 (main contribution from C8-T1)

• Passes behind the medial epicondyle

• Pierces the flexor carpi ulnaris to enter forearm

• Superficial to flexor retinaculum

• Enters hand via Guyon’s canal/ tunnel

Ulnar Nerve – Motor supply (10 muscles/muscle groups)

• Dorsal Interossei (4) - Action: Abduction of 2nd, 3rd, 4th digits away from middle finger

- Mnemonic: DAB

• Palmar Interossei (3) - Action: Adduction of 2nd, 4th, 5th digits towards middle finger, flexion of digit at MCP, extension at IP

- Mnemonic: PAD

• Adductor Pollicis - Action: Adduction of thumb

• Opponens Digiti Minimi - Action: Flexion of 5th metacarpal, lateral rotation producing opposition

• Flexor Digiti Minimi - Action: Flexion of little finger

• Abductor Digiti Minimi - Action: Abduction of little finger at

MCP joint

• Flexor Pollicis Brevis - Action: Flexion of thumb

• Flexor Digitorum Profundus (Medial half) - Action: flexion of DIP; Secondary: Flexion of joints of digits, finger, wrist

• Flexor Carpi Ulnaris - Action: Wrist flexion, ulnar deviation

• Lumbricals- 3,4 - Action: Flexion at MCP, extension at IP

Ulnar Nerve – Sensory supply

• Palmar Cutaneous Branch - Supplies medial 1⁄2 of palm

• Dorsal Cutaneous Branch - Supplies skin of dorsal aspect of medial one and half fingers

• Superficial Branch - Supplies 1⁄2 of 4th, 5th digit

Ulnar Nerve Lesion

• Cubital Tunnel Syndrome

- Compression at cubital tunnel at elbow

- Paralysis of flexor carpi ulnaris, flexor digitorum profundus (ulnar half), hypothenar eminence, interossei, and the third and fourth lumbrical muscles

- All sensations affected

- Inability to grip paper

• Guyon’s Canal Syndrome

- Sensory changes and progressive weakness of muscles innervated distal to the site

• Ulnar Claw hand

- Hyperextension at 4th,5th MCP, Flexion at 4th, 5th IP due to weakness of lumbricals and interossei

Median Nerve

• Formed from medial and lateral cord of

brachial plexus

• Nerve Roots: C5-8, T1

• Descends medial to brachial artery

• Enters forearm between two heads of pronator teres muscle

• Enters hand via carpal tunnel

Median Nerve – Motor supply (11 muscles)

• Flexor Digitorum Profundus (radial half) - Action: Flexion of DIP; Secondary: Flexion of joints of digits,

finger, wrist

• Flexor Pollicis Longus - Action: Flexion of distal phalanx of thumb

• Pronator Quadratus - Action: Pronation of forearm

• Abductor Pollicis Brevis - Action: Abduction of thumb at MCP, CMC joint

• Pronator Teres - Action: Pronation of forearm, elbow flexion

• Opponens Pollicis - Action: Opposition of thumb

• Palmaris Longus - Action: Flexion of wrist

• Lumbricals 1,2 - Action: Flexion of MCP and extension of IP

• Flexor Carpi Radialis - Action: Wrist flexion, radial deviation

• Flexor Digitorum Superficialis - Action: Flexion of PIP joint

• Flexor Pollicis Brevis - Action: Flexion of thumb

Median Nerve - Sensory Supply (2 branches)

• Palmar Cutaneous Branch - Skin of lateral two-thirds of palm

• Palmar Digital Branches - Supplies dorsal tips of 1st, 2nd, & 3rd finger, palmar skin of lateral three and half fingers

Median Nerve Injuries

• Pronator teres syndrome - Hypertrophy of pronator teres muscle can compress the median nerve. Pronator teres remains normal, but the other muscles supplied by the median nerve and the sensory distribution is affected.

• Carpal tunnel syndrome - Median nerve is compressed under the flexor retinaculum at the wrist

• Ape hand deformity - Wasting of the thenar eminence of the hand occurs because of a median nerve palsy

Musculocutaneous Nerve

• Branch of the lateral cord of brachial plexus

• Nerve Root: C5-C7

• Motor supply:

• Biceps - Action: Elbow flexion, forearm supination, flexion of arm

• Brachialis - Action: Elbow flexion

• Coracobrachialis - Action: Flexion of arm

• Sensory supply:

• Lateral cutaneous nerve of forearm: supply the skin on lateral side of forearm

Suprascapular Nerve

• Arise from upper trunk of brachial plexus

• Nerve Roots: C5-C6

• Motor supply:

• Infraspinatus - Action: Lateral rotation and abduction of arm

• Supraspinatus - Action: Shoulder abduction up to 15 degrees

Subscapular Nerve (Upper & Lower)

• Branch of posterior cord of brachial plexus

• Nerve Roots: C5-C6

• Motor supply:

• Teres Major (Lower Subscapular Nerve) - Action: Shoulder medial rotation, extension, adduction

• Subscapularis (Both Upper & Lower Subscapular Nerve) - Action: Shoulder medial rotation (when arm is by side), adduction

Lateral Pectoral Nerve

• Branch of lateral cord of brachial plexus

• Nerve Roots: C5-C7

• Motor supply

• Pectoralis Major - Action: Medial rotation, adduction,

horizontal adduction, scapular protraction, depression

• - Clavicular fibers: Shoulder flexion

- Sternocostal fibers: Shoulder extension

Medial Pectoral Nerve

• Branch of medial cord of brachial plexus

• Nerve Roots: C8, T1

• Motor supply:

• Pectoralis Minor

- Action: Downward rotation of scapula, scapular protraction, depression

Long Thoracic Nerve

• Arise from roots of brachial plexus

• Nerve Roots: C5,C6,C7

• Motor supply:

• Serratus Anterior - Action: Upward rotation of scapula, scapular protraction, depression

• Injury can cause: - Winged scapula

Thoracodorsal Nerve

• Branch of posterior cord of brachial plexus

• Nerve Roots: C6-C8

• Motor supply:

• Latissimus Dorsi - Action: Shoulder extension, adduction, medial rotation, depression and protraction of scapula

Dorsal Scapular Nerve (3 muscles)

• Arise from root of brachial plexus

• Nerve root- C5

• Motor supply:

• Rhomboid Minor - Action: Scapular elevation, retraction,

downward rotation

• Rhomboid Major - Action: Scapular elevation, retraction, downward rotation

• Levator Scapulae - Action: Scapular elevation, downward rotation

Nerve to Subclavius

• Arise from upper trunk of brachial plexus

• Nerve Roots: C5-C6

• Motor supply:

• Subclavius - Action: Depress & stabilize clavicle

Scapular Movements & Muscles

• Scapular Elevation - Upper trapezius, levator scapulae,

rhomboids

• Scapular Protraction - Serratus anterior, pectoralis minor

and major

• Scapular Depression - Serratus anterior, pectoralis minor

and major, lower trapezius, latissimus

dorsi

• Scapular Retraction - Trapezius, rhomboids

• Scapular Downward Rotation - Levator scapula, rhomboids, pectoralis minor

• Scapular Upward Rotation - Serratus anterior, trapezius (upper and lower fibers)

Spinal Accessory Nerve (CN XI)

• Motor supply

• Trapezius - Action: Upper fibers- scapula elevation,

Middle fibers- Retraction, Lower fibers- depression,

upper and lower fibers-Upward rotation

• Sternocleidomastoid - Action: Cervical lateral flexion and opposite side rotation

Superior Gluteal Nerve (3 muscles)

• Nerve Roots: L4-S1

• Motor supply:

• Gluteus Medius - Action: Abduction of hip; - Assist in medial and lateral rotation of hip

• Gluteus Minimus - Action: Abduction of hip

• Tensor Fascia Latae - Action: Flexion, abduction, medial rotation of hip

Inferior Gluteal Nerve (1 muscle)

• Nerve Roots: L5-S2

• Motor supply:

• Gluteus Maximus - Action: Hip extension & external rotation; Secondary action: Hip adduction

Nerve to Piriformis (Ventral Rami of L5-S2)

• Nerve Roots: L5-S2

• Motor supply:

• Piriformis - Action: Abduction and lateral

rotation of hip

Obturator Nerve (5 muscles)

• Nerve Roots: L2-L4

• Enters the thigh by passing through the obturator canal

• Bifurcates into anterior & posterior divisions

• Motor supply of anterior division:

• Adductor Longus - Action: Hip adduction, flexion, medial rotation

• Adductor Brevis - Action: Hip adduction, flexion, medial rotation

• Gracilis - Action: Hip flexion, medial rotation, adduction

• Motor supply of posterior division:

• Obturator Externus - Action: Hip lateral rotation,

adduction

• Adductor Magnus - Action: Hip adduction, extension,

medial rotation

Obturator Nerve – Sensory supply

• Cutaneous branch of obturator nerve supplies skin of medial thigh

Nerve to Quadratus Femoris (2 muscles)

• Nerve Roots: L4-S1

• Motor supply:

• Gemellus inferior - Action: Lateral rotation of hip

• Quadratus Femoris - Action: Lateral rotation & adduction of hip

Nerve to Obturator Internus (2 muscles)

• Nerve Roots: L5-S2

• Motor supply:

• Gemellus superior - Action: Lateral rotation of hip

• Obturator Internus - Action: Lateral rotation of hip

Sciatic Nerve (4 muscles)

• Largest branch of sacral plexus

• Nerve Roots: L4-S3

• Motor supply:

• Biceps Femoris - Action: Knee flexion, hip extension,

lateral rotation of flexed leg in non–weight bearing

• Semitendinosus - Action: Knee flexion, hip extension,

medial rotation of flexed leg in non–weight bearing

• Semimembranosus - Action: Knee flexion, hip extension,

medial rotation of flexed leg in non–weight bearing

• Adductor Magnus - Action: Hip adduction, extension,

medial rotation

Sciatic Nerve Issues

• Sciatica - Herniated disc or bone spur that compresses the sciatic nerve and cause radiating pain

• Piriformis Syndrome - Piriformis spasm or tightness compresses the sciatic nerve

Femoral Nerve

• Nerve Root: L2-L4

• Passes through femoral triangle along with femoral artery

• Motor supply:

• Iliacus - Action: Hip flexion; - Works with psoas major & psoas minor

• Pectineus - Action: Hip flexion, adduction, medial rotation

• Sartorius - Action: Hip flexion, abduction, lateral

rotation, knee flexion

• Rectus Femoris - Action: Hip flexion, knee extension

• Vastus Medialis/Intermedius/Lateralis - Action: Knee extension

Femoral Nerve – Sensory Supply (3 nerves)

• Medial Cutaneous Nerve of thigh

- Branch of anterior division of femoral nerve

- Supplies the skin on medial side of lower two third of thigh

• Intermediate Cutaneous Nerve of thigh

- Branch of anterior division of femoral nerve

- Supplies the skin on front of thigh

• Saphenous Nerve

- Branch of posterior division of femoral nerve

- Supplies the skin on the medial side of leg

Tibial Nerve (7 muscles)

• Terminal branch of sciatic nerve

• Nerve Root: L4-S3

• Motor supply:

• Superficial muscles:

- Gastrocnemius - Action: Plantarflexion, knee flexion

- Soleus - Action: Plantarflexion

- Plantaris - Action: Slight knee flexion, Plantarflexion

• Deep muscles:

- Popliteus - Action: Knee flexion, medial rotation of

flexed leg in non–weight bearing

• Tibialis Posterior - Action: Plantarflexion, Inversion

• Flexor Hallucis Longus - Action: Flexion of great toe, plantarflexion, Inversion

• Flexor Digitorum Longus - Action: 2-5 toes flexion, plantarflexion, inversion

Tibial Nerve Branch – Medial Plantar

Nerve: Motor supply

Medial Plantar nerve supplies:

• Abductor Hallucis - Action: Great toe abduction

• Flexor Hallucis Brevis - Action: 1st toe flexion

• Flexor Digitorum Brevis - Action: 2-4th toe flexion

• Lumbrical 1 - Action: MTP flexion, IP extension

Tibial Nerve Branch – Lateral Plantar

Nerve: Motor supply

Lateral Plantar nerve supplies:

• Plantar Interossei - Actions: Adduction of 3-5 toes, flexion at MTP joints

• Dorsal Interossei - Actions: Abduction of 2-4 toes, flexion at MTP joints

• Quadratus plantae - Actions: Flexion of toes

• Abductor Digiti Minimi - Actions: 5th Toe abduction and flexion

• Lumbricals 2,3,4 - Actions: MTP flexion, IP extension

• Adductor Hallucis - Action: Adduction of great toe

Tibial Nerve – Sensory Branches

• Branch from tibial Nerve and common peroneal nerve forms the sural nerve which supplies the skin over lower posterolateral leg

• Medial Calcaneal Branches - Supplies skin over heel

• Medial Plantar Nerve - Supplies skin on medial side of sole

• Lateral Plantar Nerve - Supplies skin on lateral side of sole

Common Peroneal Nerve

• Nerve Roots: L4-S2

• Originates from sciatic nerve at popliteal fossa

• Bifurcates just below the neck of the fibula into:

- Superficial peroneal nerve

- Deep peroneal nerve

Deep Peroneal Nerve – Motor supply (5 muscles)

• Nerve Roots: L4-S1

• Tibialis Anterior - Action: Dorsiflexion, inversion

• Extensor Hallucis Longus - Action: 1st toe extension, ankle dorsiflexion, inversion

• Extensor Digitorum Longus - Action: Toe extension, ankle

dorsiflexion, eversion

• Extensor Digitorum Brevis - Action: Toes extension

• Peroneus Tertius - Action: Ankle dorsiflexion, eversion

• Injury to the deep peroneal nerve

results in foot drop and unopposed eversion during gait

Superficial Peroneal Nerve – Motor supply (2 muscles)

• Nerve Roots: L4-S2

• Peroneus Longus - Action: Plantarflexion, eversion

• Peroneus Brevis - Action: Plantarflexion, eversion

Superficial & Deep Peroneal Nerves – Sensory Supply (2 nerves)

• Deep Peroneal Nerve: - Webbing between 1st & 2nd toes of foot on the dorsal surface

• Superficial Peroneal Nerve: - Dorsum of foot (Except webbing between 1st & 2nd toes)

and anterolateral part of lower leg