DERMATOMES AND MYOTOMES

-Dr.

Monica Dhanani

D E F I N AT I O N

Dermatomes:- the sensory distribution of each nerve root is called the dermatomes.

The area of the skin supplied by a single nerve root

There are 31 segments of spinal cord each with a pair of ventral and dorsal that innervate motor and sensory function resp.

The anterior and posterior nerve roots combine on each side to form the spinal nerve as they exit the vertebral canal through IV foramina

The 31 spines segment on each side give rise to 31 spinal nerves which are composed of 8C, 12T, 5L ,5S and 1C spinal nerve

Dermatomes exist for each of the spinal nerve except C1Sensory information form a specific dermatomes is

transmitted by the sensory nerve fibers to the spinal nerve of a specific segment of spinal cord

Dermatomes along the arms and legs differs from the pattern of the trunk dermatomes because they run longitudinally along the limbs

Clinical Significance dermatomes are useful to help localize

neurological levels particularly in radiculopathy.

Effacement or encroachment of a spinal nerve may or may not exhibited symptoms in dermatomic area covered by the compressed nerve root in addition to weakness or dtr loss

Viruses that infect spinal nerves such as herpes zoster reveal their origin by showing up as a pain full dermatomic area

C1- vertex of skullC2-forehead occiputC3-neck,temporal areaC4-shoulder area,clavicles,upper scapC5-deltoid, ant arm till base of thumbC6-ant arm,rad side of hand to thumb n index fingerC7-Lat arm n forearm to index,long and ring fingersC8-medial arm and forearm to long,ring and little

fingersT1-medial side of forearm to base of little fingerT2-medial side of upp arm to med elbow,pectoral

and midscapular areaT3 to T12- T3 to T6 upper thorax T5-T7 coastal margin T8-T12 abdomen and lumbar region

L1-back,over trochanter and groinL2-back,front of thigh and kneeL3-back,upper buttock,ant. thigh and

knee,medial lower legL4-medial buttock,lateral

thigh,med.leg,dorsum of foot,big toeL5-buttock,post.and lat.thigh,lat.aspect of

leg,dorsum of foot,med.half of sole,first second and third toes

S1-buttock,thigh,and leg post.S2-same as s1S3-groin,med.thigh to kneeS4-perineum,genitals,lower sacrum

D E F I N I T I O N

Myotomes:- are defined as groups of muscles supplied by a single nerve

root.

Clinical Significance Info. about the level in the spine where a

lesion may be present.Muscle weakness IV disc herniation

C1-C2 : Cervical flexionC3: Cerviacl lateral flexionC4: shoulder elevationC5: shoulder abduction C6: elbow flexionC7: elbow extensionC8: thumb extensionT1: finger abd/add

L2: hip flexionL3: knee extensionL4: ankle DFL5: great toe extensionS1: ankle Evn/hip extension/ankle PF/knee

flexionS2: knee flexion

THANK YOU