Sensory Innervation of the Lower Limb Flashcards
What is a dermatome?
area of skin supplied by a single spinal nerve root of the spinal cord segment
What is myotome?
group of muscles innervated by the ventral root a single spinal nerve
Why would the loss of a single spinal nerve root not produce any detectable sensory loss?
the adjacent dermatomes (e.g. L2, L3, L4, L5) overlap considerably
How do you detect significant sensory loss?
at least three adjacent dermatomes should be affected
Where on the limbs is there no overlap of dermatomes?
across axial lines of the limb (e.g. S2, L3, L4)
Why does damage to a peripheral nerve cause a wide range effect (large areas of skin/several muscles)?
Peripheral nerves carry nerve components from several spinal segments (or roots) to muscles and overlying skin areas
List sensation modalities that can be tested.
light touch touch localisation two point tactile discrimination pain pressure temperature vibration sterognosis passive joint movement postural sensibility
Where is the L1 dermatome?
area over inguinal ligament
Where is the L2 dermatome?
lateral side of thigh
Where is the L3 dermatome?
lower medial side of thigh
Where is the L4 dermatome?
medial side of leg, medial foot, great toe
Where is the L5 dermatome?
lateral side of leg, mid dorsum of foot and middle three toes
Where is the S1 dermatome?
little toe, lateral foot, sole foot print area
Where is the S2 dermatome?
back of upper leg and whole thigh
Where is the S3 dermatome?
area over gluteal fold
