Peripheral Nerve Injuries of the Upper Limb

Stacy Rudnicki, MD

Associate Professor of Neurology

• Aids to the Examination of the Peripheral Nervous System– WB Saunders, publishers

Definitions

Radiculopathy

• Process affecting the nerve root, most commonly by a herniated disc– Weakness in muscles supplied by the nerve

root (myotome)– Sensory loss in the area of the skin supplied

by the nerve root (dermatome)

Mononeuropathy

• Dysfunction of a single peripheral nerve– Weakness in muscles supplied by the nerve– Sensory loss in the area of the skin supplied

by the cutaneous branches of the nerve

Brachial Plexopathy

• Can refer to involvement of the entire plexus, or parts of the plexus– Trunk lesion– Cord lesion

• Distribution of weakness and numbness depends upon the part of the plexus affected

Sensory Supply to the Arm

• Because fibers from different nerve roots come together and then split apart in the plexus– A dermatome may include areas of the skin

supplied by different peripheral nerves• Example: C6

– A single nerve may supply sensation to skin covered by more than one dermatome• Example: median nerve

Sensory Supply to the Arm

• Because of the pattern of root contribution to the plexus:– An upper trunk lesion has

sensory loss in the combined C5,6 dermatomes

– A middle trunk lesion has sensory loss in the C7 dermatome

– A lower trunk lesion has sensory loss in the combined C8T1 dermatomes

Principles of Localization

• Certain sites are prone to nerve entrapments/injuries– Nerve opposing bone

• Ulnar nerve at the elbow– Closed spaces

• Carpal tunnel– Adjacent structures

• Median nerve at the elbow, adjacent to the brachial artery

Principles of localization, cont• Order in which branches arise

• Movements at specific joints

– Single nerve

• Elbow extension

– Radial

– Multiple nerves

• Elbow flexion

– Musculocutaneous

– Radial

• Thumb

– Multiple different movement accomplished by multiple muscles innervated by the median, ulnar, and radial nerves

Additional Helpful Hints• All muscles within the hand (intrinsic hand muscles)

– Are innervated by C8T1 nerve roots

– Are innervated by the lower trunk

– Are innervated by the medial cord

• All ulnar innervated muscles

– Are innervated by the C8T1 nerve roots

– Are innervated by the lower trunk

– Are innervated by the medial cord

• All axillary and musculocutanious innervated muscles

– Are innervated by C5,6 nerve roots

– Are innervated by the upper trunk

Additional Helpful Hints, cont

• Muscles inserting onto the humerus (and so related to movements of the arm) are primarily C5,6– Infraspinatus

– Supraspinatus

– Deltoid

– Teres minor

– Teres major (Plus C7)

– Pectoralis Major (plus C7)

• Latissimus is C6,7,8

Work Back from the Exam

• What muscles are weak?

• What innervates the muscle?– Peripheral nerve

– Part of plexus

• Cord

• Trunk

– Nerve roots

• Where is the sensory loss? Does it best follow the pattern of– A dermatome

– A single nerve

– A cord or trunk of the plexus

Case 1

• A 34 yo woman, currently 28 weeks pregnant, complains of numbness in her fingers

• She finds that it is more difficult to manipulate small objects

• She is awakened at night be tingling and pain in her hand which seems to spare her little finger

Case 1, continued

• On exam she has:– Mild weakness of thumb abduction and

opposition– Decreased pin prick on the palmar aspect of

the thumb, index, middle and lateral aspect of the ring finger

– No evidence of loss of muscle bulk in the hand

Case 1, continued

Finding Muscle Nerve Plexus Root

Thumb Abd APB Median Lower trunk C8T1

Medial cord

Thumb opp OP Median Lower trunk C8T1

Medial cord

Sensory loss Median --- ---

Finding Muscle Nerve Plexus Root

Thumb Abd APB Median Lower trunkC8T1

Medial cord

Thumb opp OP Median Lower trunkC8T1

Medial cord

Sensory loss ----- Median --- ---

Why isn’t this the medial cord, lower trunk, or C8T1 nerve roots?

Why isn’t this the medial cord, lower trunk, or C8T1 nerve roots?

• All should also involve ulnar innervated muscles

Why aren’t the other median innervated muscles involved?

Median Nerve

Case 1, continued

Final Diagnosis

Carpal tunnel syndrome

(median neuropathy at the wrist)

Case 2

• A 38 yo woman was the restrained passenger in a car struck head on

• She braced her hands on the dashboard immediately prior to impact

• She suffered bilateral fractures of the humerus at the spiral (radial) groove

• She complains of diffuse aches in her arms and neck and weakness in her arms

Case 2, cont

• On exam she has:– Bilateral wrist and finger drop (ie profound

weakness of wrist and finger extension at the MCPs)

– Weakness of thumb extension

– Weakness of supination

– Weakness of elbow flexion with forearm held so that thumb is toward shoulder, but not with hand held in supination

– Remainder of strength exam is normal

Sensory Loss

Case 2, cont

• Finding Muscle PN Plexus* RootWr drop ECR, ECU Radial POST C C5,6,7,8

Fing drop EDC,EI Radial POST C C7, C8

Elb flx BR Radial POST C C5,C6

Th ExtEPL, EPB Radial Post C C7,8

Sens ---- Radial --- ---

• Finding Muscle PN Plexus* Root

Wr drop ECR, ECU Radial POST C C5,6,7,8

Fing drop EDC,EI Radial POST C C7, C8

Elb flx BR Radial POST C C5,C6

Sens ---- Radial --- ---

What isn’t involved?

• If it is a Posterior Cord lesion– Axillary nerve

• Deltoid – arm abduction

• Teres Minor – lateral rotation of arm

• Radial Nerve– Why is the Triceps spared?

Triceps, long head

Triceps, lateral head Triceps, med hd

Brachioradialis

ECRL

ECRB Superficial

Supinator Radial sens

Ext Digit

Abd Pol Longus Post Interosseous

Ext Pol Longus

Ext Pol Br

Ext Indicies

Sensory loss in a high radial nerve lesion(Signficant variability b/w patients)

Final Diagnosis

Bilateral radial nerve palsies at the spiral (radial) groove related to fractures

Case 3

• A 25 year old man gets involved in a fist fight and the police arrest him

• When he is released on bail, he goes to see his doctor because he has numbness in the hand

• On exam he had– a number of scratches and bruises on both

arms– normal strength– sensory loss on the dorsum of the hand

Patient’s sensory loss

Case 3, cont

Finding PN PLEXUS Root

Sens Loss Sup Sens --- <C6

Rad

Triceps, long head

Triceps, lateral head Triceps, med hd

Brachioradialis

ECRL

ECRB Superficial

Supinator Radial sens

Ext Digit

Abd Pol Longus Post Interosseous

Ext Pol Longus

Ext Pol Br

Ext Indicies

Final Diagnosis

Superficial radial neuropathy secondary to handcuffs

Case 4

• 15 yo football player is hit be another player, with the helmet striking him in the axilla

• On getting up, he is aware of shoulder weakness and pain and is taken to the ER

Case 4, cont

• On exam he has:– Normal elbow flexion – Normal elbow extension– Normal shoulder adduction– Ability to initiate shoulder abduction, but he

cannot raise his arm more than 15 degrees– Mild weakness of external (lateral) rotation of

the arm– A patch of sensory loss over his upper arm

Case 4, sensory loss

Case 4, contFinding Muscle PN Plexus Root

Abd>15 Deltoid Axillary Post C C5,6

Ext Rot T. Minor Axillary Post C C5,6

Infrasp Suprascap UT C5,6

Sens ------- Axillary --- <C5

Case 4, continued

Finding Muscle PN Plexus Root

Abd>15 Deltoid Axillary Post C C5,6

Ext Rot T. Minor Axillary Post C C5,6

Infrasp Suprascap C5,6

Sens ------- Axillary --- <C5

Case 4, cont• If it’s at the posterior cord

– Radial innervated muscles should be affected• But elbow extension is spared

• If it’s C5,6– Other C5,6 muscles should be affected

• But elbow flexion, initiation of arm abduction spared

• Pattern of sensory loss

Case 4, Final diagnosis

Axillary Neuropathy

Case 5

• A 55 yo hospital worker comes to see you with a 2 week history of pain in her neck, which radiates into her shoulder, and upper arm

• Symptoms began when she tried to help restrain a combative patient

Case 5, cont

• On exam she she:– Weakness of shoulder abduction – Weakness of elbow flexion– Mild weakness of pronation– Sensory loss in her lateral forearm and

thumb both posteriorly and anteriorly

Case 5, continued

Finding Muscle PN Plexus Root

Arm AbdDeltoid Axillary PC C5,6

Elb Flex BC, Brach Musc LC C5,6

BR Radial PC C5,6

Pronation PT Median M & LC C6,7

Sens ----- --- --- C6

Finding Muscle PN Plexus Root

Arm AbdDeltoid Axillary PC C5,6

Elb Flex BC, Brach Musc LC C5,6

BR Radial PC C5,6

Pronation PT Median M & LC C6,7

Sens ----- --- --- C6

Case 5, Final Diagnosis

C6 Radiculopathy secondary to a

herniated disc

Case 6

• 40 yo woman comes to see you because she has noticed weakness and numbness in her right hand

• This started 2 months ago and is slowly worsening

• She is otherwise healthy, and rides her bike at lease 40 miles per week

Case 6, continued

• On exam she has:– Atrophy of the interosseous muscles of the

right hand– Mild weakness of abducting and adducting

the fingers– Normal thumb abduction, opposition and

extension– Normal wrist flexion in both a radial and

ulnar direction

Sensory Loss

Case 6 continued

Finding Muscle PN Plexus Root

Fing Add Palm Int Ulnar MCC8,T1

Fing Abd Dors Int Ulnar MCC8T1

Sens Loss ---- Ulnar --- <C8

Case 6 continued

Finding Muscle PN Plexus Root

Fing Add Palm Int Ulnar MC C8,T1

Fing Abd Dors Int Ulnar MC C8T1

Sens Loss ---- Ulnar MC <C8

Case 6 continued

• If it’s the C8 nerve root, or medial cord– other muscles affected should include:

• APB and Opponens pollicus (median)• EPL and EPB (radial)• But these muscles are spare

– more extensive sensory changes should be found

Ulnar nerve lesion

• Why is wrist flexion spared?• Why does the sensory loss not include more of

the dorsum of the hand?

Ulnar sensory loss in an ulnar lesion proximal to the midforearm

Ulnar nerveElbow

Flexor carpi ulnaris

Flex Dig Prof III/IV

Dorsal uln cut

Wrist

Adductor Pollicus Abductor

Flex Pollicus Br Opponens Digiti Minimi

Flexor

Dorsal/palmar

Interosseous

3rd/4th lumbricals

Case 5, final diagnosis

Ulnar neuropathy at the wrist

Case 7

• This 38 yo man fell off a ladder and acutely noted weakness in his right arm

• He suffered a fracture of his right clavicle• He c/o pain in the shoulder

Case 7, cont

• His exam shows:– Weakness of initiating abduction of his right arm

– If you raise his right arm to 90 degrees, he is unable to maintain it

– With his arm at his side, he is unable to externally rotate his arm

– Weakess of elbow flexion

– Numbness of the lateral arm and forearm

Case 7, cont

Finding Muscle Root Plexus Nerve

1 sh abd Supraspinatus C5,6 UT Suprascap

2 sh abd Deltoid C5,6 UT Axillary

Post Cord

Ext rot Infraspinatus C5,6 UT Suprascap

Teres minor C5,6 UT, PC Axillary

Elbow flexion Biceps C5,6 UT, LC Musc

BR C5,6 UT, PC Radial

Sensory C5 & 6 UT Axillary &

LC & PC Musc

Case 7, cont

Finding Muscle Root Plexus Nerve

1 sh abd Supraspinatus C5,6 UT Suprascap

2 sh abd Deltoid C5,6 UT Axillary

Post Cord

Ext rot Infraspinatus C5,6 UT Suprascap

Teres minor C5,6 UT, PC Axillary

Elbow flexion Biceps C5,6 UT, LC Musc

BR C5,6 UT, PC Radial

Sensory C5 & 6 UT Axillary &

LC & PC Musc

Case 7, cont• Difficult to distinguish based on exam alone if

this is upper trunk or C5 and C6 radiculopathies– Brachial plexopathies may occur with fractures of

the clavicle

– Radiculopathies are unusual without neck pain

– Preservation of the function of serratus anterior muscle makes root less likely

– Further studies (EMG) can help localize b/w root and trunk

Case 7, cont

Final diagnosis:

Upper trunk plexopathy

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