Injuries of the Brachial Plexus
Classification of Brachial Plexus Injuries
| Level | Injury | Nerve Roots |
|---|---|---|
| Upper plexus | Erb’s paralysis | C5, C6 |
| Lower plexus | Klumpke’s paralysis | C8, T1 (sometimes C7) |
| Whole plexus | Complete brachial plexus palsy | C5–T1 |
1. Erb’s Paralysis (Upper Plexus Injury)
Site of Injury
Upper trunk of the brachial plexus — specifically at Erb’s point (where six nerves meet).
Nerve Roots Involved
C5 and C6 (sometimes C7)
Mechanism / Cause
Excessive increase in the angle between the head and the shoulder (forcible separation of head and shoulder):
- Fall from a horse and landing on one shoulder
- Birth injury — excessive traction of arm during difficult delivery
- Fall on the shoulder from a height
Muscles Paralyzed
Deltoid, supraspinatus, infraspinatus, teres minor, biceps brachii, brachialis, brachioradialis, supinator, extensor carpi radialis longus (muscles supplied by C5 and C6 roots)
Deformity — “Policeman’s Tip” / “Waiter’s Tip” / “Porter’s Tip” Hand
| Limb Segment | Position | Cause |
|---|---|---|
| Arm | Adducted | Paralysis of deltoid + supraspinatus |
| Arm | Medially rotated | Paralysis of supraspinatus, infraspinatus, teres minor (lateral rotators) |
| Elbow | Extended | Paralysis of biceps brachii + brachialis |
| Forearm | Pronated | Paralysis of biceps brachii (supinator) |
Result: arm hangs limply by the side — adducted, medially rotated; forearm extended and pronated — like a policeman or waiter expecting a tip.
Sensory Loss
Minimal — along the outer (lateral) aspect of the arm (C5, C6 distribution — deltoid badge area)
Autonomic Signs
Absent (sympathetic fibres travel via C8 and T1, which are unaffected)
Reflexes Lost
- Biceps jerk (C5, C6)
- Supinator (brachioradialis) jerk (C5, C6)
2. Klumpke’s Paralysis (Lower Plexus Injury)
Site of Injury
Lower trunk of the brachial plexus (C8, T1)
Nerve Roots Involved
C8 and T1 (sometimes C7)
Mechanism / Cause
Hyperabduction of the arm — excessive upward pull of the arm:
- Clutching something with the hands after falling from a height
- Birth injury — extended arm in breech presentation
- Arm pulled into machinery
Muscles Paralyzed
- All intrinsic muscles of the hand (T1) — interossei, lumbricals, thenar, hypothenar
- Ulnar flexors of wrist and fingers (C8) — flexor carpi ulnaris, medial half FDP
Deformity — Claw Hand
Unopposed action of the long flexors and extensors:
- Hyperextension at metacarpophalangeal joints (intrinsics paralyzed → no MP flexion)
- Flexion at interphalangeal joints (long flexors intact)
- Affects all four fingers (as median nerve intrinsics also affected — T1 fibres)
Sensory Loss
Along the medial border of the forearm and hand (T1, C8 distribution)
Autonomic Signs — Horner’s Syndrome
Occurs because sympathetic fibres supplying the head and neck leave the spinal cord via T1 (the stellate ganglion fibres). When T1 is injured proximal to the white ramus communicans:
| Feature | Cause |
|---|---|
| Ptosis (partial drooping of upper eyelid) | Paralysis of superior tarsal muscle (Müller’s muscle) |
| Miosis (constriction of pupil) | Paralysis of dilator pupillae |
| Anhydrosis (absence of sweating) on face/neck | Loss of sympathetic sudomotor fibres |
| Enophthalmos (apparent recession of eyeball) | Paralysis of orbitalis (Müller’s orbital muscle) |
| Loss of cilio-spinal reflex | Loss of sympathetic control |
Horner’s syndrome = SAME = Sympathetic palsy causing Anhydrosis, Miosis, Enophthalmos (+ ptosis)
Vasomotor Changes
- Skin in the sensory-loss area is warmer (arteriolar dilation)
- Drier (absence of sweating) due to loss of sympathetic activity
Erb’s vs Klumpke’s — Comparison Table
| Feature | Erb’s Paralysis | Klumpke’s Paralysis |
|---|---|---|
| Nerve roots | C5 and C6 | C8 and T1 |
| Site | Upper trunk (Erb’s point) | Lower trunk |
| Cause | Head-shoulder separation | Arm hyperabduction / upward pull |
| Muscles paralyzed | Deltoid, supraspinatus, infraspinatus, biceps, brachioradialis, supinator, ECRL | All intrinsic hand muscles; FCU, medial ½ FDP |
| Deformity | Policeman’s/Waiter’s tip (arm adducted, medially rotated; forearm extended, pronated) | Claw hand (MP hyperextension + IP flexion, all fingers) |
| Sensory loss | Lateral aspect of arm (C5, C6) | Medial border of forearm and hand (T1, C8) |
| Autonomic signs | Absent | Present — Horner’s syndrome (T1 involvement) |
3. Injuries of Individual Nerves
Axillary Nerve Injury
Cause: Fracture of surgical neck of humerus; shoulder dislocation; direct blow Effects:
- Deltoid paralysis → loss of shoulder abduction (15°–90°)
- Flattening of shoulder (loss of deltoid contour)
- Sensory loss over lower half of deltoid (regimental badge area)
Radial Nerve Injuries
A. Injury in the Axilla — Crutch Palsy (Axillary Crutch Palsy)
Cause: Pressure of crutch top on the nerve in the axilla Effects (Motor):
- Loss of extension of elbow (triceps paralyzed)
- Wrist drop — loss of extension of wrist due to paralysis of wrist extensors
- Loss of extension of digits
- Loss of supination (extended elbow) Sensory loss:
- Back of arm, back of forearm, lateral dorsum of hand and lateral 3½ digits
B. Injury in the Spiral Groove — Saturday Night Palsy
Causes:
- Midshaft fracture of humerus (radial nerve lies in direct contact with bone in spiral groove)
- Pressure from prolonged arm-over-chair-back — drunkard falling asleep (Saturday night paralysis)
- Wrongly placed intramuscular injection in mid-arm
Important: The injury usually occurs distal to the origin of the nerves to the long and lateral heads of triceps → so extension of elbow is preserved (or slightly weak)
Effects (Motor):
- Wrist drop (main feature — loss of wrist extension)
- Loss of extension of fingers
- Loss of supination (extended elbow) Sensory loss:
- Restricted to a small area over dorsum of hand between 1st and 2nd metacarpals (1st web space)
C. Injury at the Elbow — Radial Tunnel Syndrome
Cause: Entrapment of the deep branch (posterior interosseous nerve) at the radial tunnel — Arcade of Frohse, fibrous bands, tendinous margin of ECRB, leash of radial recurrent vessels Effects:
- Loss of extension of wrist and fingers
- No wrist drop (ECRL intact — supplied above the elbow)
- Pain over the extensor aspect of the forearm
Median Nerve Injuries
A. Carpal Tunnel Syndrome (Most Common Entrapment Neuropathy)
Cause: Compression of median nerve within the carpal tunnel beneath the flexor retinaculum Predisposing factors: Hypothyroidism, rheumatoid arthritis, pregnancy, obesity, repetitive wrist movement
Effects:
- Burning pain / tingling / “pins and needles” in lateral 3½ fingers — worse at night
- No sensory loss over thenar eminence (palmar cutaneous branch passes superficial to retinaculum — unaffected)
- Weakness of thenar muscles
- Ape thumb deformity (Simian’s hand) — if untreated; thumb adducted and extended in the plane of palm (cannot oppose); due to paralysis of thenar muscles (APB, OP, FPB)
Tests: Tinel’s sign (tapping over carpal tunnel → tingling in median distribution); Phalen’s test (wrist flexion 60 seconds → symptoms reproduced)
B. High Median Nerve Injury (Above Elbow)
Deformity: Benediction attitude / Pope’s blessing hand — index and middle fingers remain extended when asked to make a fist (FDP lateral half paralyzed); ring and little fingers flex normally
Ulnar Nerve Injuries
Injury at the Medial Epicondyle (Most Common Site)
Cause: Fracture of medial epicondyle; repetitive leaning on elbow; cubital tunnel syndrome
Effects (Motor):
- Loss of FCU → wrist deviates radially on flexion
- Loss of medial ½ FDP → ring and little fingers cannot flex at DIP joints
- Paralysis of all interossei, 3rd + 4th lumbricals, hypothenar muscles, adductor pollicis
Deformity — Ulnar Claw Hand (Partial Claw Hand):
- Ring and little fingers show: hyperextension at MCP joints + flexion at IP joints
- Index and middle fingers less affected (1st + 2nd lumbricals intact via median nerve)
- Hence “partial” or “ulnar claw hand”
Froment’s Sign:
- Patient asked to grasp a card between thumb and index finger
- Pulls the card → distal phalanx of thumb flexes (to compensate for paralyzed adductor pollicis)
- Positive Froment’s sign = adductor pollicis paralysis (ulnar nerve injury)
Sensory loss: Medial 1½ fingers and medial palm (palmar and dorsal surfaces)
Combined Median + Ulnar Nerve Injury — Complete (True) Claw Hand
- Affects all four fingers
- Hyperextension at all MCP joints + flexion at all IP joints
- No normal lumbrical function → complete clawing
Long Thoracic Nerve Injury (Nerve of Bell)
Cause:
- Sudden downward pressure on the shoulder
- Carrying heavy loads on the shoulder
- Axillary node dissection (surgical risk)
Effects:
- Winging of the scapula — medial border of scapula becomes prominent and lifts away from the chest wall (serratus anterior paralyzed → rhomboids pull medial border medially)
- Loss of pushing and punching actions
- Arm cannot be raised beyond 90° (serratus anterior needed for overhead abduction — to rotate glenoid upward)
Viva Pearls — Injuries
- Erb’s = C5, C6 = “waiter’s tip” = autonomic signs absent
- Klumpke’s = C8, T1 = claw hand = Horner’s syndrome (present if T1 proximal to white ramus)
- Horner’s syndrome = ptosis + miosis + anhydrosis + enophthalmos
- Saturday night palsy = spiral groove injury = wrist drop + triceps spared (nerves to triceps arise proximal to groove)
- Crutch palsy = axilla injury = wrist drop + triceps paralyzed
- Carpal tunnel = median nerve = lateral 3½ digits; ape thumb; night pain; thenar eminence spared
- Ulnar claw = ring + little fingers (partial); complete claw = median + ulnar combined
- Froment’s sign = positive in ulnar nerve injury (adductor pollicis paralysis)
- Winging of scapula = long thoracic nerve injury = serratus anterior paralysis
- Radial tunnel syndrome at elbow = no wrist drop (ECRL intact)