Dermatomes mine

an area of skin supplied primarily by sensory fibers from a SINGLE spinal nerve root

dermatome

muscle or group of muscles supplied by a specific spinal nerve

myotome

what are the four options for documentation of dermatomes

normal, diminished, absent, altered

to assess myotomes, the joint is placed in ___ ___ to optimize muscle function and the patient holds position against 5 seconds of sustained resistance

mid range

myotomes use ___ ____ contractions

resisted isometric

normal strength for myotome

5

movement against some resistance for myotome

4

movement against gravity for myotome

3

minimal to no movement for myotome

2

what is the representative movement for C5

shoulder aduction

what is the representative movement for C6

wrist extension

what is the representative movement for C7

elbow extension

what is the representative movement for C8

finger flexion, thumb abduction

what is the representative movement for T1

finger abduction

what is the representative movement for L2

hip flexion

what is the representative movement for L3

knee extension

what is the representative movement for L4

ankle dorsiflexion

what is the representative movement for L5

great toe extension

what is the representative movement for S1

ankle plantarflexion

what is the representative muscle for C5

deltoid, supraspinatus

what is the representative muscle for C6

extensor carpi radialis longus, brevis

what is the representative muscle for C7

triceps brachii

what is the representative muscle for C8

flexor pollicis longus, flexor digitorum profundus

what is the representative muscle for T1

dorsal interossei

what is the representative muscle for L2

iliopsoas

what is the representative muscle for L3

quadriceps

what is the representative muscle for L4

tibialis anterior

what is the representative muscle for L5

extensor hallucis longus

what is the representative muscle for S1

gastrocnemius, soleus

what is C5-C6 representative of

elbow flexion

what is the C4 dermatome

AC joint

what is the C5 dermatome

lateral elbow

what is the C6 dermatome

dorsal surface thumb

what is the C7 dermatome

dorsal surface index

what is the T1 dermatome

medial elbow

what is the T2 dermatome

apex axilla

what is the C1-2 myotome action

cervical flexion

what is the C3 myotome action

cervical lateral flexion

what is the S2 myotome action

knee flexion

what is the L1 dermatome

upper anterior thigh

what is the L2 dermatome

mid anterior thigh

what is the L3 dermatome

medial femoral condyle

what is the L4 dermatome

medial malleolus

what is the L5 dermatome

dorsum of great toe

what is the S1 dermatome

lateral malleolus

what is the S2 dermatome

popliteal fossa

Dermatome

A strip of skin innervated by a single spinal nerve

(these nerve fibres may travel through dif. peripheral nerves)

Dermatome derive from somite cells

Myotome

Group of muscles innervated by a single spinal nerve root

Derive from somite cells

(myotome is part of somite that develops into muscle)

Dermatomes are of great clinical importance. Why?

There is some overlap, but sensory abnormalities in the dermatomes can allow you to work out if the spinal cord is damaged, and which spinal nerve is damaged

Origin of dermatomes and myotomes

Embryogenesis

Day 20 = trilaminar disc, middle layer is mesoderm, paraxial mesoderm is next to neural tube

After day 20 = paraxial mesoderm differentiates into 44 pairs called "somites", 13 break down, left with 31 pairs of somites

Correspond to 31 pairs of spinal nerves

Ventral somite portion - scelerotome

(ribs + vertebral column)

Dorsal somite - dermomyotome

Myotome proliferates

Dermatome disperses into dermis

Limb growth, dermatome associate with growing limb is stretched and moved down limb, creating segmental innervation

(Keegan and Garrett dermatome map of 1948)

Dermatome maps

Depict dermatome distribution

Show progression of limb growth around an axial line

The general pattern is similar in all people, but significant variations exist in dermatome maps from person to person.

Axial line

The line between two adjacent dermatomes that are not represented by immediately adjacent spinal levels. Although dermatomes are shown to be discrete segments on dermatomal maps, they are in fact not; adjacent dermatomes overlap with one another

Once leaving the spinal cord, nerves divide and branch, and the branches combine with branches from other roots to form ...

A new nerve

Eg. median nerve at elbow contains nerve fibres from different spinal roots

EG of virus infection and link with dermatomes?

Herpes Zoster

"shingles"

Viral infection of spinal nerve

Dormant in dorsal root ganglion, activates and spreads along sensory nerve to affect only area of skin (dermatome) supplied by that nerve

*Viruses that infect spinal nerves can outline dermatomes well

The 31 spine segments give rise to ...

(..cervical, ..thoracic, ..lumbar, ..sacral, ..coccygeal)

Dermatomes exist for each spinal nerve, except ....

Sensory info. from specific dermatome is transmitted by ... to spinal nerve of specific...

... nerve roots emerge ... respective vertebrae

... nerve root emerges between ...

Remaining nerve roots emerge ... respective vertebrae

Along the thorax and abdomen, the dermatomes are ..., each supplied by ...

Dermatomes along the ... differ from pattern of trunk dermatomes - because ...

31 spinal nerves on each side (31 pairs)

8, 12, 5, 5, 1

first cervical spinal nerve

sensory nerve fibers

specific segment of the spinal cord

C1-C7 above

C8 between C7 and T1 vertebrae

below

evenly spaced segments stacked up on top of each other

by a different spinal nerve.

arms and legs

dermatomes run longitudinally along limbs

Myotomes:

Most muscles of the upper and lower limb are made up of a number of myotomes. Why?

Muscles of upper/lower limb tend to be innervated by more than one spinal nerve root

EG: biceps brachii muscle.

Innervated by the musculocutaneous nerve and able to perform flexion at the elbow.

Musculocutaneous nerve is derived from C5, C6, C7 nerve roots.

All three of these spinal nerve roots can be said to be associated with elbow flexion.

Myotome function can be tested clinically and graded (0 = complete paralysis, 5 = normal movement)

to see if spinal cord damage, and where the damage is located.

Movements MOST STRONGLY associated with each myotome:

C5 - Elbow flexion

C6 - Wrist extension

C7 - Elbow extension

C8 - Finger flexion

T1 - Finger abduction

L2 - Hip flexion

L3 - Knee extension

L4 - Ankle dorsiflexion

L5 - Great toe extension

S1 - Ankle plantarflexion

C2 Dermatome/Myotome

D: Temple, forehead, occiput

M: Neck Flexion

C3 Dermatome/Myotome

D: Entire neck, posterior cheek, temporal area, prolongation forward under mandible

M: Neck Side Flexion

C4 Dermatome/Myotome

D: Shoulder area, clavicular area, upper scapular area

M: Shoulder Elevation

C5 Dermatome/Myotome

D: Deltoid area, anterior aspect of entire arm to base of thumb

M: Shoulder Abduction

C6 Dermatome/Myotome

D: Anterior arm, radial side of hand to thumb and index finger

M: Elbow Flexion & Wrist Extension

C7 Dermatome/Myotome

D: Lateral arm and forearm to index, long, and ring fingers

M:

C8 Dermatome/Myotome

D: Medial arm and forearm to long, ring, and little fingers

M:

T1 Dermatome/Myotome

D: Medial side of forearm to base of little finger

M:

T2 Dermatome/Myotome

D: Medial side of upper arm to medial elbow, pectoral and mid scapular areas

M:

T3-T12 Dermatomes/Myotomes

D: T3-T6: upper thorax

T5-T7: costal margin

T8-T12: abdomen and lumbar region

M:

L1 Dermatome/Myotome

D: Back, over trochanter and groin

M:

L2 Dermatome/Myotome

D: Back, front of thigh to knee

M:

L3 Dermatome/Myotome

D: Back, upper buttock, anterior thigh and knee, medial lower leg

M:

L4 Dermatome/Myotome

D: Medial buttock, lateral thigh, medial leg, dorsum of foot, big toe

M:

L5 Dermatome/Myotome

D: Buttock, posterior and lateral thigh, lateral aspect of leg, dorsum of foot, medial half of sole, first second and third toes

M:

S1 Dermatome/Myotome

D: Buttock, thigh and posterior leg

M:

S2 Dermatome/Myotome

D: Buttock, thigh and posterior leg

M:

S3 Dermatome/Myotome

D: Groin, medial thigh to knee

M:

S4 Dermatome/Myotome

D: Perineum, genitals, lower sacrum

M:

S5 Dermatome/Myotome

D: Perianal area

M: