Axillary and Radial Nerve Quiz

Upper Extremity & Lower Extremity Nerves

• These notes cover the nerves of the upper and lower extremities.

Axillary Nerve

• Branch: Posterior cord of brachial plexus

• Nerve Roots: C5-C6

• Motor Supply: Teres minor, deltoid (anterior, posterior, acromial fibers)

  • Action: Shoulder abduction, horizontal abduction, extension, external rotation

• Sensory Supply: Upper lateral cutaneous nerve of arm, skin covering the lower half of deltoid and upper part of long head of triceps

• Causes of Injury: Dislocation of the shoulder, fracture of the surgical neck of humerus

  • Effects: "Square shoulder" from deltoid muscle atrophy, sensory loss over lower half of deltoid

Radial Nerve

• Branch: Posterior cord of brachial plexus

• Nerve Roots: C5-8, T1

• Motor Supply: Extensor muscles of the forearm & wrist, supinator, triceps, brachioradialis

  • Action: Wrist extension, radial deviation, elbow extension, supination

• Sensory Supply: Lower lateral cutaneous nerve of arm, posterior cutaneous nerve of the arm, posterior cutaneous nerve of forearm, superficial branch, skin of lateral half of dorsum of hand, lateral two and half digits including thumb.

• Radial Nerve Injury: Axilla, musculospiral groove, around radial neck

  • Radial Tunnel Syndrome: Tenderness in the extensor muscle mass of the forearm (distal to lateral epicondyle), pain on long finger extension test
  • Posterior interosseous nerve syndrome:
  • Wrist drop: Loss of extension.

Ulnar Nerve

• Branch: Medial cord of brachial plexus

• Nerve Roots: C7-T1 (main contribution from 8-T1)

• Motor Supply: Dorsal and palmar interossei, adductor pollicis, flexor carpi ulnaris, flexor digitorum profundus (medial half)

  • Action: Hand/finger adduction, thumb adduction, wrist flexion, flexion of DIP of medial digits

• Sensory Supply: Palmar cutaneous branch (medial ½ of palm), dorsal cutaneous branch (dorsal aspect of medial one and half fingers), superficial branch (½ of 4th & 5th digits)

• Ulnar Nerve Lesion

  • Cubital Tunnel Syndrome: Compression in cubital tunnel at elbow
    • Effects: Sensory loss, progressive weakness of innervated muscles distal
  • Guyon's Canal Syndrome: Sensory changes, progressive weakness of distal muscles

Median Nerve

• Origin: Medial and lateral cord of the brachial plexus

• Nerve Roots: C5-8, T1

• Motor Supply: Flexor digitorum profundus (radial half), flexor pollicis longus, pronator quadratus, pronator teres, opponens pollicis, palmar interossei, lumbricals (1 & 2), flexor carpi radialis, flexor digitorum superficialis

  • Action: Elbow flexion, wrist flexion, hand/finger flexion, thumb opposition

• Sensory Supply: Palmar cutaneous branch, palmar digital branches (dorsal aspects of 1st, 2nd & 3rd finger), palmar skin of lateral 3 and ½ fingers

• Median Nerve Injuries:

  • Pronator syndrome: Compression by hypertrophy of pronator teres muscle
  • Carpal Tunnel Syndrome: Compression of median nerve under flexor retinaculum at the wrist

Musculocutaneous Nerve

• Branch: Lateral cord of brachial plexus
• Nerve Roots: C5-C7
• Motor Supply: Biceps, coracobrachialis, brachialis
  • Action: Elbow flexion, forearm supination, flexion of arm
• Sensory Supply: Lateral cutaneous nerve of forearm supplies skin on lateral side of forearm.

Suprascapular Nerve

• Origin: Upper trunk of brachial plexus
• Nerve Roots: C5-C6
• Motor Supply: Infraspinatus, supraspinatus
  • Action: Lateral rotation and abduction of arm, Shoulder abduction up to 15 degrees

Subscapular Nerve (Upper & Lower)

• Branch: Posterior cord of brachial plexus
• Nerve Roots: C5-C6
• Motor Supply: Teres Major (lower subscapular nerve), subscapularis (both upper and lower subscapular nerve)
  • Action: Shoulder medial rotation, extension, adduction, and when arm is by side, adduction

Lateral Pectoral Nerve

• Branch: 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: Medial cord of brachial plexus
• Nerve Roots: C8, T1
• Motor Supply: Pectoralis Minor
  • Action: Downward rotation of scapula, scapular protraction, depression

Long Thoracic Nerve

• Origin: Roots of brachial plexus
• Nerve Roots: C5, C6, C7
• Motor Supply: Serratus anterior
  • Action: Upward rotation of scapula, scapular protraction, depression
• Injury: Winged scapula

Thoracodorsal Nerve

• Branch: Posterior cord of brachial plexus
• Nerve Roots: C6-C8
• Motor Supply: Latissimus Dorsi
  • Action: Shoulder extension, adduction, medial rotation, depression, protraction of scapula

Dorsal Scapular Nerve

• Origin: Brachial plexus
• Nerve Root: C5
• Motor Supply: Rhomboid minor, rhomboid major, levator scapulae
  • Action: Scapular elevation, retraction, downward rotation

Nerve to Subclavius

• Origin: Upper trunk of brachial plexus
• Nerve Roots: C5-C6
• Motor Supply: Subclavius
  • Action: Depress & stabilize clavicle

Scapular Movements & Muscles

• Elevation: Upper trapezius, levator scapulae, rhomboids
• Protraction: Serratus anterior, pectoralis minor, and major
• Depression: Serratus anterior, pectoralis minor, and major, lower trapezius, latissimus dorsi
• Retraction: Trapezius, rhomboids
• Downward Rotation: Levator scapula, rhomboids, pectoralis minor
• Upward Rotation: Serratus anterior, trapezius (upper & lower fibers)

Spinal Accessory Nerve (CN XI)

• Motor supply: Trapezius (upper fibers- scapula elevation, middle fibers-retraction, lower fibers-depression, upper and lower fibers-upward rotation), sternocleidomastoid (cervical lateral flexion and opposite side rotation)

Superior Gluteal Nerve

• Nerve Roots: L4-S1
• Motor Supply: Gluteus medius, gluteus minimus, tensor fascia latae
  • Action: Abduction of hip, assists in medial and lateral rotation of hip, abduction of hip, flexion, abduction and medial rotation of hip.

Inferior Gluteal Nerve

• Nerve Roots: L5-S2
• Motor Supply: Gluteus maximus
  • Action: Hip extension & external rotation, secondary action- hip abduction

Nerve to Piriformis (Ventral Rami of L5-S2)

• Nerve Roots: L5-S2
• Motor Supply: Piriformis
  • Action: Abduction and lateral rotation of hip

Obturator Nerve

• Nerve Roots: L2-L4
• Motor Supply: Adductor longus, adductor brevis, gracilis, obturator externus, adductor magnus
  • Action: Hip adduction, flexion, medial rotation (anterior division), hip lateral rotation, adduction, medial rotation (posterior division)

Nerve to Quadratus Femoris

• Nerve Roots: L4-S1
• Motor Supply: Gemellus inferior, quadratus femoris
  • Action: Lateral rotation of hip and adduction of hip

Nerve to Obturator Internus

• Nerve Roots: L5-S2
• Motor Supply: Gemellus superior and Obturator internus
  • Action: Lateral rotation of hip

Sciatic Nerve

• Largest Branch: Sacral plexus
• Nerve Roots: L4-S3
• Motor Supply: Biceps femoris, semitendinosus, semimembranosus, adductor magnus
  • Action: knee flexion, hip extension, lateral rotation of flexed leg (non-weight bearing)

Sciatic Nerve

• Sciatica: Herniated disk or bone spur compressing the sciatic nerve, causing radiating pain
• Piriformis Syndrome: Piriformis spasm or tightness compressing the sciatic nerve

Femoral Nerve

• Nerve Root: L2-L4
• Pathway: Passes through the femoral triangle, along with the femoral artery
• Motor Supply: Iliacus, pectineus, sartorius, rectus femoris, vastus medialis/intermedius/lateralis
  • Action: Hip flexion, knee extension, hip flexion, adduction, medial rotation, hip flexion, abduction, lateral rotation, knee flexion, hip flexion, knee extension and hip flexion respectively.

Femoral Nerve - Sensory Supply

• Medial Cutaneous Nerve of Thigh: Supplies medial side of lower two-thirds of thigh.
• Intermediate Cutaneous Nerve of Thigh: Supplies anterior thigh skin.
• Saphenous Nerve: Supplies the medial side of the leg.

Tibial Nerve

• Terminal Branch: Sciatic nerve
• Nerve Roots: L4-S3
• Motor Supply: Gastrocnemius, soleus, tibialis posterior, flexor hallucis longus, flexor digitorium longus, plantar interossei, and lumbrical 1.
  • Actions: Plantarflexion, knee flexion, plantar flexion, slight knee flexion and plantar flexion.

Tarsal Tunnel Syndrome

• Posterior tibial nerve compression or irritation within the tarsal tunnel

Tibial Nerve Branch - Medial Plantar Nerve

• Motor Supply: Abductor hallucis, flexor hallucis brevis, flexor digitorium brevis, lumbrical 1.
  • Actions: Great toe abduction, 1st toe flexion, 2-4th toe flexion, MTP flexion and IP extension

Tibial Nerve Branch - Lateral Plantar Nerve

• Motor Supply: Plantar interossei, dorsal interossei, Quadratus plantae, Abductor digiti minimi, lumbricals 2, 3 & 4, Adductor hallucis
  • Actions: Adduction of toes, abduction of toes, 2-4th toe flexion, flexion of toes, 5th toe abduction & flexion, MTP flexion, IP extension, and great toe adduction respectively.

Tibial Nerve - Sensory Branches

• Medial Calcaneal Branches: Supplies skin over the heel.
• Medial Plantar Nerve: Supplies medial side of sole
• Lateral Plantar Nerve: Supplies lateral side of sole.

Common Peroneal Nerve

• Nerve Roots: L4-S2
• Origin: Sciatic nerve
• Bifurcation: Just below the fibular neck into superficial and deep peroneal nerves.

Deep Peroneal Nerve

• Nerve Roots: L4-S1
• Motor Supply: Tibialis anterior, extensor hallucis longus, extensor digitorum longus, extensor digitorum brevis, peroneus tertius.
  • Actions: Dorsiflexion, inversion, 1st toe extension, ankle dorsiflexion, inversion, toe extension, ankle dorsiflexion and eversion.

Superficial Peroneal Nerve

• Nerve Roots: L4-S2
• Motor Supply: Peroneus longus, peroneus brevis
  • Action: Plantarflexion and eversion.

Superficial & Deep Peroneal Nerves - Sensory Supply

• Deep Peroneal Nerve: Supplies webbing between 1st and 2nd toes on the dorsal surface.
• Superficial Peroneal Nerve: Supplies dorsum of foot (except webbing between 1st and 2nd toes) and anterolateral portion of lower leg.