Peripheral Nerve Injuries of the Upper Limb Stacy Rudnicki, MD Associate Professor of Neurology

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 –A single nerve may supply sensation to skin covered by more than one dermatome

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

Dermatomes of the Posterior Arm

Dermatomes of the Anterior Arm

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

Case 1 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 1, cont On exam she has: –Bilateral wrist and finger drop (ie profound weakness of wrist and finger extension at the MCPs) –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 –She has numbness in the posterior forearm extending into dorsum of hand into thumb and proximal index finger

Case 1, cont FINDINGMUSCLEROOTPLEXUSP N WR DROPECR, ECUC7, C8POST CRADIAL MT, LT FING DRPEDC,EIC7, C8POST CRADIAL MT, LT ELB FLXBRC5,C6POST CRADIAL UT SENS ----C6LAT CRADIAL UT

Triceps, long head Triceps, lateral headTriceps, med hd Brachioradialis ECRL ECRBSuperficial SupinatorRadial sens Ext Digit Abd Pol LongusPost 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 2 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 2, cont FINDINGROOTPLEXUSPN SENS LOSS< C6< LAT CORDSUP RAD SENS

Triceps, long head Triceps, lateral headTriceps, med hd Brachioradialis ECRL ECRBSuperficial SupinatorRadial sens Ext Digit Abd Pol LongusPost Interosseous Ext Pol Longus Ext Pol Br Ext Indicies

Final Diagnosis Superficial radial neuropathy secondary to handcuffs

Case 3 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 3, 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 3, sensory loss

Case 3, cont FINDINGMUSCLEROOTPLEXUSPN Abd>15DeltoidC5,6Post CAxillary UT Ext RotT. MinorC5,6Post CAxillary InfraspC5,6UTSuprascap Sens <C5<POST CAxillary <UT

C5 C6 C7 C8 T1

Case 3, cont If it’s at the posterior cord –Radial innervated muscles should be affected But elbow extension is spared If it’s at the upper trunk –Musculocutaneous innervated muscles should be affected But elbow flexion is spared Pattern of sensory loss

Case 3, Final diagnosis Axillary Neuropathy in the Axilla

Case 4 A 55 yo hospital worker comes to see you with a 2 week history of pain in her neck, shoulder, and upper arm Symptoms began when she tried to help restrain a combative patient

Case 4, 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 4, cont

Case 4, Final Diagnosis C6 Radiculopathy secondary to a herniated disc

Case 5 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 5, cont 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, abduction and adduction

Case 5, sensory loss

CASE 5, cont

Case 5, cont If it’s the lower trunk, C8/T1, or medial cord other muscles affected should include: –APB and Opponens pollicus (median) –EPL and EPB (radial) Can it be localized further to a specific site of the ulnar nerve?

Ulnar sensory loss in an ulnar lesion proximal to the midforearm

Ulnar nerve Elbow Flexor carpi ulnaris Flex Dig Prof III/IV Dorsal uln cut Wrist Adductor PollicusAbductor Flex Pollicus BrOpponens Digiti Minimi Flexor Dorsal/palmar Interosseous 3rd/4th lumbricals

Case 5, final diagnosis Ulnar neuropathy at the wrist