6. MYOTOMES &
DERMATOMES
Myotomes
Each muscle in the
body is supplied by
a particular level or
segment of the
spinal cord and by
its corresponding
spinal nerve.
Dermatomes
~Greek for"skin
cutting"
~An area of the skin
supplied by specific
nerve fibers.
Sensory
7.
8. Dermatomes and Myotomes
Dermatome-
sensory region of skin
innervated by a nerve root
Myotome- muscles innervated by a single
nerve root
9. Common Dermatomal Levels
C5-
Shoulder
C6-
Lateral Arm and Digits 1&2
C7-
Middle Digit
C8-
Digits 4 & 5
15. Neurologic Level C5
The muscles found
within this myotomal
pattern are the deltoid
and the biceps brachii.
Because the latter is
also innervated by C6,
the deltoid is the most
"pure" C5 muscle.
One of the most
commonly used tests
for shoulder abduction
is to instruct the patient
to flex the elbow at 90
degrees, then offer
gradual resistance to
abduction
16. Neurologic Level C6
the biceps brachii is
innervated by C5 and
C6. C6 also innervates
the most powerful wrist
extensors, carpi radialis
longus and brevis,
which do radial
extension. To test for
wrist extension, stabilize
the patient’s forearm
and wrist extension
17. Neurologic Level C7
The muscles found
within this myotomal
pattern are the triceps,
wrist flexors. The
triceps muscle primarily
does elbow extension.
A common test for this
action is to ask the
patient to fully flex the
arm, offer firm, constant
resistance until
discerning the
maximum resistance
h/she can overcome.
18. Neurologic Level C8:
The muscles found
within this myotomal
pattern are finger
flexors—flexor
digitorum superficialis,
flexor digitorum
profundis, and the
lumbricals. To test for
finger flexion, the
patient fully flexes h/her
fingers at all joints while
you curl your fingers
into them. Ask the
patient to resist your
attempt to pull h/her
fingers out of flexion.
19. Neurologic level T1:
The muscles found
within this myotomal
pattern are those
involved in finger
abduction—dorsal
interossei and abductor
digiti minimi, and
adduction—palmar
interossei.
To test for finger
adduction, ask the
patient to extend h/her
fingers and hold a piece
of paper (or a dollar bill)
between two of h/her
fingers. Then you pull it
out
20.
21. Neurologic Levels T12 to L3:
The muscles found
within this myotomal
pattern are the
iliopsoas, quadriceps,
and the adductors
Because this myotomal
pattern includes
multiple muscle groups
an injury to this nerve
root level can be more
easily evaluated by
sensory testing of the
dermatomal patterns.
22. Neurologic Level L4:
The muscle
predominantly
innervated at this root
nerve level is the tibialis
anterior, which does
dorsiflexion.
Instruct the patient to
dorsiflex and invert
h/her foot. With your
free hand, hold the
patient’s foot and ask
h/her to resist your
attempt to move the
foot into plantarflexion
23. Neurologic Level L5:
The muscles found
within this myotome
are the extensor
hallucis longus (big
toe extensor) &
extensor digitorum
(heel walk)
24. Neurologic Level S1:
The muscles found
within this myotome
are the peroneus
longus (eversion) &
peroneus brevis
(eversion)