The Brachial Plexus
Definition: Plexus of nerves formed by anterior (ventral) rami of C5, C6, C7, C8, and T1. (Little contribution from C4 & T2).
Variations:
- Prefixed: Large contribution from C4, T2 absent.
- Postfixed: Large contribution from T2, C4 absent.
Components & Location
Schematic of Brachial Plexus Roots, Trunks, Divisions, and Cords
| Component | Formation / Detail | Location |
|---|---|---|
| 1. Roots (5) | Anterior primary rami of C5-T1. | Neck (Deep to Scalenus Anterior) |
| 2. Trunks (3) |
Upper (C5+C6) Middle (C7 alone) Lower (C8+T1) |
Neck (Cleft between Scalenus Medius & Anterior) |
| 3. Divisions | Anterior & Posterior divisions for each trunk. | Behind Clavicle |
| 4. Cords (3) |
Lateral: Ant. div of Upper + Middle. Medial: Ant. div of Lower. Posterior: Post. div of all three. |
Axilla |
Branches
A. Supraclavicular Branches (From Roots & Trunks)
- From Roots:
- Long Thoracic N. / Nerve to Serratus Anterior (C5, C6, C7)
- Dorsal Scapular N. / Nerve to Rhomboids (C5)
- Others: Muscular branches to Scalene/Longus colli; contribution to Phrenic.
- From Trunks (Upper Trunk Only):
- Suprascapular Nerve (C5, C6)
- Nerve to Subclavius (C5, C6)
B. Infraclavicular Branches (From Cords)
| Lateral Cord | Medial Cord | Posterior Cord |
|---|---|---|
|
1. Lat. Pectoral N. 2. Lat. Root of Median N. 3. Musculocutaneous N. |
1. Med. Pectoral N. 2. Med. Cutaneous N. of Arm 3. Med. Cutaneous N. of Forearm 4. Med. Root of Median N. 5. Ulnar N. |
1. Radial N. 2. Axillary N. 3. Thoraco-dorsal N. (Latissimus dorsi) 4. Upper Subscapular N. 5. Lower Subscapular N. |
Clinical Correlation: Lesions
Erb’s point: Junction of six nerves
Erb's Point: Region on Upper Trunk where 6 nerves meet (C5 root, C6 root, Suprascapular n., N. to Subclavius, Ant. Division, Post. Division).
1. Erb's Paralysis (Upper Plexus Injury)
Injury of the upper brachial plexus leading to excessive increase in the angle between the head and shoulder: A, fall from the height and landing on a shoulder; B, Traction of the arm and hyperextension of the neck.
- Site of Injury: Upper Trunk (C5, C6).
- Cause: Undue separation of head from shoulder (e.g., birth injury, fall on shoulder).
- Deformity: Policeman's / Waiter's Tip Hand.
- Arm: Adducted & Medially rotated.
- Elbow: Extended.
- Forearm: Pronated.
Policeman receiving a tip position of the upper limb in Erb's paralysis.
- Key Muscles Paralyzed: Deltoid, Biceps brachii, Brachialis, Brachioradialis.
- Sensory Loss: Small area over lower part of deltoid (Regimental Badge area / C5) and outer arm (C6).
2. Klumpke's Paralysis (Lower Plexus Injury)
Injury of the lower brachial plexus leading to excessive increase in the angle between the trunk and shoulder: A, sudden upward pull of the arm; B, arm pulled during delivery.
- Site of Injury: Lower Trunk (C8, T1).
- Cause: Hyperabduction of arm (e.g., clutching a tree branch while falling, breech delivery).
- Deformity: Claw Hand (Main en griffe).
- Hyperextension at MCP joints & flexion at IP joints.
- Key Muscles Paralyzed: Intrinsic muscles of hand (Interossei, Thenar, Hypothenar) and Ulnar flexors of wrist/fingers.
- Sensory Loss: Medial border of Forearm & Hand (T1).
- Associated Signs: Horner's Syndrome (Ptosis, Miosis, Anhydrosis) due to involvement of T1 sympathetic fibers.
Segmental Control Overview
- Shoulder Adduction / Elbow Flexion: C5, C6
- Shoulder Abduction / Elbow Extension: C6, C7
- Wrist & Finger Flexion: C8, T1
📚 Ref:Vishram Singh - Upper Limb and Thorax
💬 Comments
No comments:
Post a Comment