MSK Dermatomes and Myotomes Flashcards
What is a dermatome?
An area of skin supplied by the nerves originating from a single spinal root
What is a myotome?
A group of muscles that a single spinal nerve innervates
How would you test dermatomes and how (2)?
1) Sensation - cotton bud
2) Pain - pin
Why would you test a dermatome?
Spinal damage or cord lesion (would damage all nerves below that lesion).
How would you test for C7?
Middle finger
Where would you test for L3?
Just above the knee
Point to where C5, C6, C7, C8, T1, T2 dermatomes are tested for
C5 - axillary - badge area C6 - thumb C7 - middle finger C8 - little finger T1 - medial forearm T2 - medial arm
What would you do before performing a dermatome test on the patient?
Introduce yourself Explain Answer questions Gain consent Wash hands
Skin and muscle that have a common spinal nerve supply have come from what embryologically?
The same dermatomyotome
C1-C7 exit ________ corresponding vertebra. T1-L5 exit ________ corresponding vertebra
Above
Below
One spinal nerve supplies___(one/many)____ myotome. One spinal nerve contains _____(One/many)____ motor units
One
Many
Is there functional overlap of dermatomes across the axial line?
No but there is functional overlap just not over the axial line
What is the relevance of Varicella zoster virus and dermatomes?
It normally affects one dermatome of the skin - chicken pox virus
How would you test dermatomes for L1, L2, L3, L4, L5, S1 and S3 dermatomes?
L1 ant thigh L2 below that L3 just above knee L4 medial malleolus L5 Great toe S1 Heel S2 Ischial tuberosity
How would you test the myotomes for C5, C6, C7, C8, T1?
C5 - abduction of the shoulder, lateral rotation and weak contribution to elbow flexion
C6 - Elbow flexion, wrist extension, supination, medial rotation of shoulder
C7 - Elbow extension, wrist flexion, pronation, weak contribution to finger flexion and extension
C8 - Finger flexion, finger extension, thumb extension, write ulnar deviation
T1 - Finger abduction and adduction
