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Quiz for thosewho have not

taken it already

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Spinal

nerves – 31

pairs,

emerging ateach

vertebral

level

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Figure 13-10: The Cervical Plexus

Cranial nerves

Transverse cervical nerve

Great auricular nerve

Accessory

nerve (XI)

Hypoglossal

nerve (XII)

Lesser occipital nerve

Supraclavicular nerves

Clavic le 

Sternothyroid muscle 

Sternohyo id musc le 

Phrenic nerve

Omohyoid musc le 

Ansa cervicalis

C1

C2

C3

C4

C5

Thyrohyo id musc le 

Geniohyo id musc le 

Nerve roots of

cervical plexus

Cervical Plexus

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Brachial Plexus

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MYOTOMES & DERMATOMES

Myotomes

Each muscle in the

body is suppliedby a particular

level or segment

of the spinal cord

and by itscorresponding

spinal nerve. 

Dermatomes

~Greek for"skin

cutting"~An area of the

skin supplied by

specific nerve

fibers.

Sensory 

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Dermatomes and Myotomes

Dermatome- sensory region of skin

innervated by a nerve root

Myotome- muscles innervated by a single

nerve root

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Common Dermatomal Levels

C5- Shoulder

C6- Lateral Arm and Digits 1&2

C7- Middle Digit

C8- Digits 4 & 5

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Common Dermatomal Levels

L4- Anteromedial Shin

L5- Anterolateral Shin, dorsum of foot to

 big toe

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Common Dermatomal Levels

S1- toe, lateral foot, sole and calf

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ASIA, 2006

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 Neurologic Level C5

The muscles foundwithin this myotomalpattern are the deltoidand the biceps brachii.Because the latter isalso innervated by C6,the deltoid is the most"pure" C5 muscle.

One of the most

commonly used testsfor shoulder abductionis to instruct the patientto flex the elbow at 90degrees, then offer

gradual resistance toabduction

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 Neurologic Level C6

the biceps brachii isinnervated by C5 andC6. C6 also innervates

the most powerful wristextensors, carpi radialislongus and brevis,which do radialextension. To test for

wrist extension,stabilize the patient’sforearm and wristextension

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 Neurologic Level C7

The muscles foundwithin this myotomalpattern are the triceps,

wrist flexors. Thetriceps muscle primarilydoes elbow extension.

 A common test for thisaction is to ask the

patient to fully flex thearm, offer firm, constantresistance untildiscerning themaximum resistance

h/she can overcome.

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 Neurologic Level C8:

The muscles foundwithin this myotomalpattern are fingerflexors—flexordigitorum superficialis,flexor digitorumprofundis, and thelumbricals. To test forfinger flexion, the

patient fully flexes h/herfingers at all joints whileyou curl your fingersinto them. Ask thepatient to resist yourattempt to pull h/herfingers out of flexion.

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 Neurologic level T1:

The muscles foundwithin this myotomalpattern are thoseinvolved in fingerabduction—dorsalinterossei and abductordigiti minimi, andadduction—palmarinterossei.

To test for finger

adduction, ask thepatient to extend h/herfingers and hold a pieceof paper (or a dollar bill)between two of h/her

fingers. Then you pull itout

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 Neurologic Levels T12 to L3:

The muscles foundwithin this myotomalpattern are theiliopsoas, quadriceps,and the adductorsBecause this myotomalpattern includesmultiple muscle groupsan injury to this nerve

root level can be moreeasily evaluated bysensory testing of thedermatomal patterns.

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 Neurologic Level L4:

The musclepredominantlyinnervated at this root

nerve level is the tibialisanterior, which doesdorsiflexion.

Instruct the patient todorsiflex and invert

h/her foot. With yourfree hand, hold thepatient’s foot and askh/her to resist yourattempt to move the

foot into plantarflexion

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 Neurologic Level L5:

The muscles found

within this myotome

are the extensorhallucis longus (big

toe extensor) &

extensor digitorum

(heel walk)

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 Neurologic Level S1:

The muscles found

within this myotome

are the peroneuslongus (eversion) &

peroneus brevis

(eversion)

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