U01.11.004 Brachial plexus lesions

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Learning Objectives

  • Differentiate between Erb palsy and Klumpke palsy based on root involvement and mechanism.
  • Identify the anatomical structures involved in Thoracic Outlet Syndrome.
  • Recognize the clinical presentation of a winged scapula and its common surgical causes.

 

1. Upper Trunk Lesion: Erb Palsy (C5–C6)

Also known as Erb-Duchenne palsy, this results from an increased angle between the neck and shoulder.

  • Causes: Lateral traction on an infant’s neck during delivery or trauma in adults (e.g., falling on the head/shoulder).
  • Muscle Deficits:
    • Deltoid & Supraspinatus: Loss of abduction (arm hangs by side).
    • Infraspinatus: Loss of lateral rotation (arm medially rotated).
    • Biceps brachii: Loss of flexion and supination (arm extended and pronated).
  • Presentation: The classic “waiter’s tip” position.

 

2. Lower Trunk Lesions: Klumpke Palsy & TOS (C8–T1)

These lesions affect the intrinsic muscles of the hand, leading to a functional loss of the lumbricals.

  • Klumpke Palsy: Caused by upward traction on the arm (e.g., grabbing a tree branch to break a fall or delivery traction).
    • Deficit: Total claw hand (MCP joints extended, DIP/PIP joints flexed).
  • Thoracic Outlet Syndrome (TOS): Compression of the lower trunk and subclavian vessels, often within the scalene triangle.
    • Causes: Cervical ribs or a Pancoast tumor at the lung apex.
    • Presentation: Hand muscle atrophy plus ischemia/edema from vascular compression.

3. Winged Scapula (Long Thoracic Nerve, C5–C7)

The Serratus anterior is responsible for anchoring the scapula to the thoracic cage.

  • Injury: Often occurs during axillary node dissection after mastectomy or from stab wounds.
  • Functional Deficit: Inability to anchor the scapula; the patient cannot abduct the arm above the horizontal position (> 90°).

Clinical Notes & Corrections:

  • Scalene Triangle: The trunks of the brachial plexus and the subclavian artery pass between the anterior and middle scalene muscles. The subclavian vein passes outside (anteromedially to) this triangle.
  • Pancoast Tumor: Always consider this in an older smoker presenting with Klumpke-like symptoms and potentially Horner syndrome.

Activity: Brachial Plexus Lesion

Memory Hooks:

Erb: Herb gets DIBs on tips (Deltoid, Infraspinatus, Biceps).

Klumpke: Clawmpke (Total claw hand).

Nerve Roots: C5-C6-C7 wings of heaven (Long Thoracic).

Plexus: Remember To Drink Cold Beer (Roots, Trunks, Divisions, Cords, Branches).

Activity: