2. Dermatomes:- the sensory distribution of each nerve
root is called the dermatomes.
The area of the skin supplied by a single nerve root
3. ⚫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 C1
⚫Sensory 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
4. 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
5. ⚫C1- vertex of skull
⚫C2-forehead occiput
⚫C3-neck,temporal area
⚫C4-shoulder area,clavicles,upper scap
⚫C5-deltoid, ant arm till base of thumb
⚫C6-ant arm,rad side of hand to thumb n index finger
⚫C7-Lat arm n forearm to index,long and ring fingers
⚫C8-medial arm and forearm to long,ring and little fingers
⚫T1-medial side of forearm to base of little finger
⚫T2-medial side of upp arm to med elbow,pectoral and
midscapular area
⚫T3 to T12-
⚫
⚫
T3 to T6 upper thorax
T5-T7 coastal margin
T8-T12 abdomen and lumbar region
6.
7. ⚫L1-back,over trochanter and groin
⚫L2-back,front of thigh and knee
⚫L3-back,upper buttock,ant. thigh and knee,medial lower
leg
⚫L4-medial buttock,lateral thigh,med.leg,dorsum of
foot,big toe
⚫L5-buttock,post.and lat.thigh,lat.aspect of leg,dorsum of
foot,med.half of sole,first second and third toes
