Upper Limb Nerve Injuries😊

Nerve Injuries

Structure of Nerve

• Nerve components from outer to inner:
• Epineurium: Outermost layer, surrounds the entire nerve.
• Fascicle: Bundles of nerve fibers.
• Perineurium: Surrounds each fascicle.
• Endoneurium: Innermost layer, surrounds individual nerve fibers (axons).
• Axon: Nerve fiber that transmits electrical signals.

Classification of Nerve Injuries

• Two main classifications:
• Seddon's classification
• Sunderland's classification



• 1 → Molecular Level → Recoverable anoxia / Myelin sheath
• 2 → Axon disrupture
• 3 → Axon disrupture + Endoneurium
• 4 → Axon disrupture + Endoneurium + Perineurium
• 5 → Axon disrupture + Endoneurium + Perineurium + Epineurium



 

Seddon's Classification

• Tinel's sign: 
• Percussion from distal to proximal direction
• → nerve stimulation
• sensations distal to neuroma → tingling.

• Motor march: 
• Gradual recovery of muscle function
• from proximal to distal,
• typically seen in axonotmesis.

• High vs. low nerve injury: 
• Higher (more proximal) injuries
• → greater disability and deformities.

Wallerian Degeneration & Denervation Hypersensitivity

• Occurs after complete transection of a peripheral motor nerve

• Leads to loss of neural input to muscle

Wallerian degeneration

• Type of orthograde degeneration

• Starts at site of injury

• Progresses distally toward nerve terminal

• Interrupts neural transmission

• Proximal axon may show retrograde degeneration

Denervation hypersensitivity

• Skeletal muscle becomes extremely sensitive to ACh

• Due to marked upregulation of nicotinic ACh receptors

• Receptors spread beyond the motor end plate

• Even tiny amounts of ACh cause exaggerated response

Peripheral Nerve Injuries (Upper Limb)

NOTE

• Thoraco-dorsal nerve (aka nerve to latissimus dorsi):
• Passes along with the subscapular artery.

Axillary Nerve Injury (aka Surgeon's nerve)

• Branch of: Posterior cord of the brachial plexus.

• Root value: C5, C6.

Course:

1. After formation, it passes through the Quadrangular Space.

2. Winds around the surgical neck of the humerus.

3. Gives a branch to the shoulder joint.

4. Divides into two terminal divisions: 
1. Anterior 
2. Posterior
• Gives branches
• continues as the upper lateral cutaneous nerve of the arm.

Innervation:

• Motor: 
• Deltoid (abduction of shoulder),
• Teres minor (external rotation of shoulder).

• Sensory: 
• Regimental badge sign
• sensory loss at
• Lateral aspect of proximal shoulder

• Deformity: 
• Adducted & internally rotated shoulder.
• flabby and flat shoulder
• loss of contour of the shoulder joint

Mechanism of injury: 

• Shoulder dislocation
• (most common),

• Fracture of the surgical neck of the humerus
• proximal humerus fracture

• iatrogenic injury.
• Intramuscular injections

Musculocutaneous Nerve Injury

• Nerve to the anterior compartment of the arm.

• Entry:
• Pierces coracobrachialis
• enter the anterior compartment.

• Muscles Supplied
• Flexion of elbow AND Adduction of shoulder
• Biceps brachii (C5, C6):
• Flexion of elbow,
• supination of forearm.
• Brachialis (C5, C6):
• Flexion of elbow.
• Coracobrachialis (C5, C6, C7) :
• Adduction of shoulder.

• Mneumonic: Muscle (MC Nv) in BC (Biceps brachii, Coracobrachialis) Boy (Brachialis). His Ex (Extended) was Pro (Pronated)

• Continuation
• Becomes the lateral cutaneous nerve of the forearm.
• Sensory: 
• Lateral aspect of forearm
• (paresthesia, tingling, numbness).

Deformity: 

• Extended elbow with pronated forearm.

Mechanism of injury: 

• Shoulder dislocation.

Median/Labourer's Nerve Injury

C5 - T1

 

• Type: Mixed nerve.

Motor supply:

• Forearm: 
• Anterior compartment EXCEPT
• flexor carpi ulnaris
• medial half of flexor digitorum profundus.

• Hand: 
• All thenars EXCEPT
• adductor pollicis
• lumbricals 1 & 2.

Sensory supply:

• palmar aspect
• Lateral 3 1/2 fingers

• dorsal aspect
• Only tips of lateral 3 1/2 fingers

Autonomous zone: 

• Tip of index finger
• most reliable for testing median nerve

Anterior Interosseous Nerve (AIN)

• Branch: Branch of median nerve.

• Type: Purely motor nerve.

Supplies:

• Flexor FPL
• Flex DIP at thumb

• Lateral half of FDP
• Flex DIP at
• index
• middle fingers

AIN injury:

• Cause: D/t supracondylar humerus fracture.

• Features: No sensory deficit.

Sign: 

• Kiloh Nevin sign/ weak OK sign



• inability to form an 'O' shape with
• thumb
• index finger
• due to weakness of FPL and FDP > Opponens pollicis

• Mneumonic:
• Meddel (Med N) kitti → Flex (Flexors) cheyth nadannu → alkkar Ayinu (AIN) enn choich → ninte Foreplaym (FPL) DP (FDP) yum kollilla nn prnj → Njn Weakly OK (Ok sign) nn prnj

Volkmann's ischemic contracture

Median Nerve Injury at Wrist

Features:

• Loss of sensation of lateral 3 1/2 fingers.

• Wasting of thenar eminence.

• Loss of thumb: abduction, flexion, opposition
• leading to Ape hand/thumb deformity.
• due to unopposed Adductor Pollicis

Pen test:

• Evaluates: 
• Abduction of thumb (Abductor pollicis brevis).

• Procedure: 
• With palm facing upwards,
• patient asked to touch a pen with the thumb.

• Positive: 
• If patient fails to do so.

• Mnemonic:
• Middle (Median N) irunna 1 kilo (Kiloh nevin) pazham thinnunna Ape (Ape thumb) ne Pen (Pen test) Point (Pointing index) cheyth vilichu

Median Nerve Injury at Elbow

Manifestations: 

• Wrist lesion manifestations + loss of functions of:
• FPL (flexor pollicis longus)
• FDS (flexor digitorum superficialis)
• FDP (flexor digitorum profundus, lateral half)

Pointing Index/Benediction sign/Pope sign/Ochsner clasp sign:

• Mnemonic: Pope () ocha (ochsner) vach class edukkum

Evaluates:

• FDS: Flexion of PIP & MCP joints.

• FDP: Flexion of DIP, PIP, MCP joints.

Observation: 

• Index finger doesn't flex on making a fist in median nerve injury at elbow.

Note actions of thumb:

• Abduction: Perpendicular to plane of palm.

• Extension: Parallel to plane of palm.

Ulnar/Musician's Nerve Injury

• Runs medially

• Pass through 2 canals
• Cubital Tunnel
• At Elbow → between 2 heads of Flexor carpi ulnaris
• (Cubital fossa → Median nerve)
• In the forearm → Supplies FCU and Medial part of FDP
• Guytons canal → At wrist

• After Guytons canal → divide into Superficial and Deep branch
• Superficial branch → Sensory supply to Skin of Medial 1 1/2 hand (+ Palmaris brevis)
• Deep branch → Hypothenar + Interrossei + Medial 2 lumbricals + Adductor pollicis (graveyard of ulnar nerve)

Sensory supply:

• Medial 1 1/2 fingers (volar & dorsal).

• Autonomous zone: Tip of little finger.

Motor supply:

• Arm: No supply.

• Forearm:
• Medial half of FDP.
• Flexor carpi ulnaris.

• Hand:
• Hypothenar muscles.
• Adductor pollicis (thenar muscle).
• Interossei group of muscles.
• Lumbricals 3 & 4.

Ulnar Nerve Injury at Wrist (Guyon's canal)

• Site: 
• Guyon's canal
• behind the pisohamate ligament.

Manifestations:

• Affects intrinsic muscles of the hand

• Partial clawing of hand
• AKA Main en griffe
• due to lumbricals 3 & 4 paralysis,
• hyperextension at
• MCP joints
• flexion at
• IP joints of ring and little fingers

• Hypothenar wasting.

• Loss of sensations in medial 1 1/2 hand.

• Loss of palmar & dorsal interossei function.

Note: 

• Complete clawing = Median + Ulnar nerve palsy.

Treatment for claw hand: 

• Knuckle bender splint.

Evaluation of Ulnar Nerve Injury:

• Ulna → Ullinn vanna Ego (Egawa) → karanma card () vach books () vangi → fan (fanning) itt iruinn padich

Card test:

• Evaluates: Palmar interossei (adduction of fingers).

• Procedure: 
• Patient holds a card between their fingers
• examiner tries to pull it away.
• Failure to hold suggests weakness.

Egawa test:

• Evaluates: 
• Dorsal interossei (abduction of 2nd, 3rd, 4th, 5th fingers).

• Procedure: 
• Patient asked to abduct their fingers.

Fanning of fingers: 

• To evaluate dorsal interossei.

Book test:

• Evaluates: Adductor pollicis.

• Procedure: 
• Patient asked to hold an object (e.g., spoon, piece of paper)
• between thumb & index finger.

• Froment sign:
• adductor pollicis → paralyzed
• flexor pollicis longus (median nerve supply) compensates
• flexion of the thumb IP joint.

NOTE:

ㅤ	Waardenburg Syndrome
ㅤ	• White forehead • Piebaldism + • Dystopia canthorum • Cochlear deafness. • Heterochromia iridis. Bald (Piebald) ayittulla Wardernu (Wardenburg) Vote kodutha Aarada (Vogt Harada)
ㅤ	Vogt Koyanagi Harada (VKH) Syndrome:
CF	• Granulomatous Panuveitis
Age	• Third or fourth decade
Signs	• Sunset glow fundus • Perilimbal Vitilligo: Suiguira sign
3 Phases	1. Meningoencephalitic phase (Distinguished) 2. Uveitis and Choroiditis (Distinguished) 3. Leukoderma, poliosis, and alopecia
ㅤ	Sympathetic ophthalmitis
CF	• Granulomatous Panuveitis
Signs	• Retrolental Flare • Dalen Fuchs nodules
Pathology	ㅤ
↳ Exciting Eye	• Eye that sustains initial injury. • Penetrating Trauma • Affecting ciliary body
↳ Sympathizing Eye	• The fellow eye, not initially injured. • Develops after 2 weeks (>2 weeks) from initial trauma.
Treatment	• Steroids
Prevention	• Enucleation of the traumatic eye within 14 days

• Granulomatous Panuveitis seen in
• Sympathetic Ophthalmitis
• VKH syndrome

• Wardenberg syndrome

• Wartenburg sign
• Involuntary abduction of little finger at rest
• Loss of hypothenar function → Digiti minimi

• Wartenburg syndrome
• Radial cutaneous nerve
• Also called Cheiralgia paresthetica.
• Both Warts in Hand

---

Type	Cause
Posterior	• Lowe syndrome ↳ Oculo Cerebro Renal syndrome • Opacity at posterior capsule center
Anterior	SAW Spina bifida Alport syndrome Waardenburg syndrome

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Fuchs Terms	Notes
Fuchs heterochromia iridocyclitis	Chronic AU ⇒ • U/L Diffuse Iris atrophy + Heterochromia + Posterior SCC • Painless, No redness, No posterior synechiae Positive Amsler's Sign: ◦ Bleeding into Anterior chamber on paracentesis ◦ Without trauma to Iris/Angle ◦ D/t abnormal fragile Iris Stellate Keratin Precipitates ↳ Herpetic uveitis ↳ Toxoplasmosis ↳ Fuchs Heterochromia Iridocyclitis • Young stella → Fucked () by Toxic () Herpes () Guy
Dalens Fuchs	• Seen in Sympathetic ophthalmitis ↳ (granulomatous panuveitis) • Dalen Fucked Granny () sympathetically ()
Foster Fuchs	• In Pathological Myopia • Bleeding at macula • Fucking in Foster () home ↳ Blind child (Pathological myopia) ↳ Bled (Bleeding at macula)
Fuchs Endothelial dystrophy	• Cornea guttata: • Wart-like excrescences on posterior cornea • Fuck her Guts→ endothelial Stages • Stage 1: Central corneal guttata that spreads peripherally • Stage 2: Corneal oedema - beaten metal-like appearance • Stage 3: Bullous keratopathy • Stage 4: Subepithelial scarring and superficial vascularization

 

Ulnar Nerve Injury at Elbow

• Site: 
• Cubital tunnel,
• behind medial condyle.

• Manifestation: 
• Decreased clawing/deformity (ulnar paradox).

Ulnar Paradox

Radial Nerve Injury

 

ECRL → Car long trip → radial N (Long n)

ECRB → Tennis elbow

 

Supply:

• Triceps (elbow extensors)

• forearm extensors.

Course

• Pass medial to humerus and supply triceps

• Pass through radial groove and supply triceps again

• Above elbow → supply 1 extensor of forearm→ ECRL
• ECRL helps in extending the wrist joint

• Below elbow → divides into superficial and posterior interosseous N
• Superficial Branch → Sensory → Supply dorsum of hand
• Deep branch → Posterior interosseous nerve (PIN) → All extensors (posterior compartment) of forearm except ECRL

Autonomous zone: 

• Dorsum of first web space.

Superficial branch: 

• Sensory supply to dorsum of medial
• lateral 3 1/2 fingers excluding tips.

Posterior Interosseous Nerve (PIN): 

• Deep motor branch,
• supplies extensors of fingers and thumb.

• No sensory branches

Levels of Radial Nerve Injury

Types of Radial Nerve Injuries

• ”Mneumonic:
• Ridiculously long
1. Radial N supplies all extensors of arm, forearm and hand
2. C5 → T1

Holstein Lewis Fracture

• Most common cause of radial nerve injury.

• Mechanism: 
• Lower 1/3rd humerus fracture → causes radial nerve entrapment.

• Mnemonic: HL → Humerus Lower → High Radial N injury

Manifestations: 

• Wrist drop, finger drop, thumb drop, sensory loss.

Treatment:

• Cock-up splint: For wrist drop.

• Static splint: 
• Extends wrist.

• Dynamic splint: 
• Extends wrist + allows flexion of fingers,
• prevents contractures.
• Preferred

Summary of Nerve Function Tests

Brachial Plexus

• Origin: Ventral rami of C5 C6 C7 C8 T1.

• Sequence: Roots → Trunks → Divisions → Cords → Branches.

• Trunk Formation:
• C5 and C6 combine to form → Upper trunk.
• C7 continues as → Middle trunk.
• C8 and T1 combine to form → Lower trunk.

• Divisions:
• All trunks split into:
• Anterior division.
• Posterior division.
• No branches arise directly from divisions.

• Cord Formation:
• Posterior divisions of upper, middle, and lower trunks → Posterior cord.
• Anterior divisions of upper and middle trunks → Lateral cord.
• Anterior division of lower trunk → Medial cord.

Branches🌿

From Roots

Winging of Scapula 🦋

• Injury site: Long thoracic nerve 🩺

• Nerve roots: C5 C6 C7

• Muscle affected: Serratus anterior

• Sign: Medial border of scapula more prominent ⬆️

From Trunks

From Cords

Brachial Plexus Injury

Erb's Point (A)

• Confluence of:
• C5 nerve root
• C6 nerve root
• Suprascapular nerve

Types of Brachial Plexus Injuries

• Supraclavicular injury
• upper roots & trunks
• Erb's palsy (Best prognosis).

• Infraclavicular injury
• lower roots & trunks
• Klumpke's palsy (Worst prognosis).

• Combined/mixed palsy: 
• Worst prognosis.

Mechanism of Injury

• Traction (stretching):
• Supraclavicular injury (most common): 
• During birth,
• RTA/fall.
• Infraclavicular injury: 
• Hyperabduction injury
• (fall from height while holding onto an object),
• traction on arm during birth.

Erb's Palsy

 

• Arm:
• Adducted
• medially rotated

• Elbow: Extended

• Forearm: Pronated

• Fingers: Flexed

• Sensory Loss:
• Over the lateral aspect of the forearm.

• Causes:
• Birth injury 👶
• Shoulder dystocia (injury while overstretching)
• Fall on shoulder ⬇️

Deformity: 

• "Policeman's/Waiter's/Porter's Tip" deformity
• Porter → Transport bus le conductor

• Treatment: Airplane splint.

Nerves injured and deformities: 

• Injury to upper trunk of brachial plexus

• Nerve root: C5 C6
• ”Mneumonic: Erbs paralysis → 5.6kg ulla child SAM → C5, C6

• (Mnemonic: SAM):
• Suprascapular nerve
• Deformties
• Supraspinatus: Adduction.
• Infraspinatus: Internal rotation.
• Axillary nerve
• Deformties
• Deltoid: Adduction.
• Teres minor: Internal rotation.
• Musculocutaneous nerve
• Deformties
• Biceps brachii: Elbow extension, pronation.
• Brachialis: Elbow extension.

Coracobrachialis

• Is spared in Erbs palsy

• Supplied by C5, C6, C7

• Due to nerve supply from C7 (only C5, C6 is affected in Erbs Palsy)

Klumpke's Palsy

• Injury to lower trunk of brachial plexus

• Nerve roots injured: C8, T1.

• Mneumonic:
• Plum Cake (Kllumke) kandapo → Horny (Horners) ayi → cake nte Midlle (Median) il Alli (Ulnar) Claw (Claw hand) vach
• Plum cake nu 800 Rs (C8, T1)

Results in:

1. Combined ulnar + median nerve palsy
• Complete clawing of hand.
• Hyperextension of metacarpophalangeal joint
• Flexion at interphalangeal joint

2. Loss of sympathetic supply to eye (T1)
• Parasympathetic overactivity on eye
• Horner's syndrome 



• Ptosis (drooping eyelid)
• Miosis (small pupil)
• Anhidrosis (no sweating)

• Claw hand (C8, T1) > Horner’s syndrome (T1)

Treatment: 

• Plexus reconstruction.

• Definition: Nerve trapped under a structure → delayed conduction of stimulus/injury.

Carpal Tunnel Syndrome (CTS)

Definition: 

• Median nerve entrapment
• carpal tunnel (at wrist)
• under flexor retinaculum/transverse carpal ligament.

• Most common entrapment neuropathy
• (most common entrapped nerve: median nerve).

Affected

• Digital branch affected
• Leads to sensory loss over digits.

• Sparing of palmar cutaneous branch (pass above carpal tunnel)
• Sensations over the palm are preserved in CTS

Etiology

• (conditions causing increased pressure inside carpal tunnel):
• Idiopathic: Most common cause.
• Hypothyroidism (myxedema).
• Rheumatoid arthritis (inflammation).
• Pregnancy (fluid retention).
• Acromegaly (excessive growth of bone & soft tissue).
• Activity causing wrist compression (e.g., typing).
• Colle's fracture (hematoma → compression).
• Gout.
• Amyloidosis.
• Diabetes mellitus.

Clinical features:

• Middle-aged female.

• Complaint of pain: 
• Burning, tingling & numbness.
• Distribution: Along lateral 3 1/2 fingers.
• Maximum at night.
• Relieved by shaking her hand (Flick sign).

• Thenar muscle wasting & weakness.

Evaluation:

• Mnemonic: Tunnel (CTS) nte mukalil kude Duke (Durkan) il fast (Phalens) ayi poi
1. Phalen's test:
• Position held for approx. 1 minute
• wrist in full flexion
• Produces dull aching pain, numbness, paresthesia, tingling along median nerve distribution.
2. Reverse Phalen's test:
• Position held for approx. 1 minute
• wrist in full extension, hands pressed together
• Reproduces symptoms similar to Phalen's test.
3. Durkan's test:
• Best clinical test.
• Direct median nerve compression
• between thenar & hypothenar eminence
• for 30 seconds → reproduces symptoms.
4. Tourniquet test.

Investigation of choice (IOC).

• Nerve conduction studies

Treatment:

• Conservative: Rest, steroids, splints.

• Surgery (if no improvement with conservative Rx): 
• Release of flexor retinaculum.

Nerve Injuries Table