BRACHIAL PLEXUS --- MNEMONICS

BRACHIAL PLEXUS --- MNEMONICS

Introduction

The Brachial Plexus is a network of nerve fibers that run from the spine, passing through the cervico-axillary canal to reach axilla.  It is formed by the ventral rami of the lower four cervical and first thoracic nerve roots (C5-C8, T1). Sometimes C4 may also be involved.

Function

The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve (CN XI) and an area of skin near the axilla innervated by the intercostobrachial nerve.

Description

Path

The brachial plexus is divided into Roots, Trunks, Divisions, Cords, and Branches. There are five "terminal" branches and numerous other "pre-terminal" or "collateral" branches that leave the plexus at various points along its length.

• The five Roots are the five anterior rami of the of the lower four cervical and first thoracic nerve roots (C5-C8, T1), after they have given off their segmental supply to the muscles of the neck.
• These Roots merge to form three Trunks:
  • Upper Trunk (C5-C6)
  • Middle Trunk (C7)
  • Lower Trunk (C8, T1)

• Each Trunk then splits into anterior and posterior divisions, to form six Divisions.   The anterior/ posterior divisions innervate flexor groups versus extensor groups:
  • anterior divisions of the upper, middle, and lower trunks
  • posterior divisions of the upper, middle, and lower trunks
• These six Divisions will regroup to become the three Cords. The Cords are named by their position with respect to the axillary artery.
  • The Posterior Cord is formed from the three posterior divisions of the trunks (C5-C8,T1)
  • The Lateral Cord is the anterior divisions from the upper and middle trunks (C5-C7)
• The Medial Cord is simply a continuation of the anterior division of the lower trunk (C8,T1)

MNEMONICS----

LATERAL CORD:-  (LML)

1.LATERAL PECTORAL

2.MUSCULOCUTANEOUS

3.LATERAL ROOT OF MEDIAN NERVE

POSTERIOR CORD:- (ULNAR)

1.UPPER SUBSCAPULAR

2.LOWER SUBSCAPULAR

3.NERVE TO LATISSIMUS DORSI

4.AXILLARY 

5.RADIAL

MEDIAL CORD:- (M4U)

1.MEDIAL PECTORAL NERVE

2.MEDIAL ROOT OF THE MEDIAN NERVE

3.MEDIAL CUTANEOUS NERVE OF ARM

4. MEDIAL CUTANEOUS NERVE OF FOREARM

5.ULNAR

Some more mnemonics for remembering the branches:

Posterior Cord Branches:-
STAR - subscapular (upper and lower), thoracodorsal, axillary, radial.
ULTRA - upper subscapular, lower subscapular, thoracodorsal, radial, axillary

Lateral Cord Branches:-
LLM "Lucy Loves Me" - lateral pectoral, lateral root of the median nerve, 
                    musculocutaneous

Medial Cord Branches:-
MMMUM "Most Medical Men Use Morphine" - medial pectoral, medial
                     cutaneous nerve of arm, medial cutaneous nerve of forearm, ulnar, 
                     medial root of the median nerve.