First mnemonic to be remembered is RTDC
RTDC stands for Roots, Trunks, Divisions and then Cord.
C5, C6, C7, C8, T1 Nerve roots contribute in the formation of
brachial plexus.
Draw first diagram as given below to depict the nerve roots
in a simple manner.
C5---------
C6-----------C7-----------
C8----------
T1-----------
C7 root to continue as middle trunk
Join C8 and T1 to form the lower trunk.
Then each trunk divides into anterior and posterior
divisions.
Anterior division of upper trunk and anterior division of
middle trunk join to form Lateral cord.
Anterior divison of the lower trunk forms the Medial cord.
Posterior divisions of all the three trunks join to form the
Posterior cord.
Once you understand the formation and nomenclature of RTDC,
then it will be easy to remember the names and root values of nerves of the
upper limb which are the branches of the brachial plexus.
Another mnemonic to be remembered : LLM,
4 MU & ULTRA
LLM are the nerves
arising from the lateral cord ( Lateral Pectoral Nerve, Lateral root of Median
nerve and Musculo cutaneous nerve). Since C5,6 & 7 roots had contributed in
the formation of lateral cord, so the root value Lateral pectoral nerve and
Musculocutaneous nerves are C5,6 & 7. Usculocutaneous nerve supplies all
three muscles of the flexor compartment of arm( BBC,i.e., Biceps, Brachialis
and Coracobrachialis).
4MU are the nerves from
the Medial Cord. Medial Pectoral Nerve, Median root of median Nerve, Medial
cutaneous nerve of arm , Medial cutaneous nerve of forearm, and Ulnar Nerve (
Root value C7,T1)
ULTRA is the mnemonic for
the nerves of the posterior cord. ULTRA stands for Upper subscapular nerve,
Lower subscapular nerve, Thoracodorsal nerve ( Nerve to Latissimus dorsi
muscle, root value C7, C8), Radial nerve and Axillary nerve. Radial nerve is
basically the continuation of the posterior cord and because posterior cord is
formed by joining of the posterior divisions of all, upper, middle and lower
trunks, the root value of radial nerve is C5 to T1.
Once you understood the basic
detail about the formation of brachial plexus, then you should also remember
that two nerves arise from the root itself. These two nerves are Dorsal
scapular nerve and Long thoracic nerve.
Dorsal scapular nerve root value
is C5
Long Thoracic Nerve arises form
C5, C6 and C7 and it supplies to serratus anterior muscle. Its injury results
in winging of scapula.
Two nerves arise from the trunk: Suprascapular
nerve and nerve to subclavius. These two nerves arise from the upper trunk.
Now, it is easy to recall that the C5 and C6 roots join to form the upper trunk
which divides into anterior and posterior division. But, trunk it self gives
origin to suprascapular nere and Nerve to subclavius.
