Nerve Palsies

Question 1

!!! Musculocutaneous nerve palsy clinical features and deformity? (3)

Answer 1

• Sensory: numb over lateral forearm
• motor: ant compartment arm (Biceps, brachialis, coracobrachialis) paralysis, with very weak elbow flexion and forearm supination (biceps. Supinator muscle still work thanks to post interosseous nerve from radial nerve). Absent biceps reflex.
• deformity: usually elbow extension with forearm pronation. Wasting ant compartment arm.

Question 2

!!! axillary nerve palsy clinical features and deformity? (3)

Answer 2

• Sensory: numbness over “sergeant’s patch “ over lower part deltoid
• motor: paralysis of deltoid leading to very weak shoulder abduction from 15-90 degrees. Weak shoulder flexion and extension. Paralysis teres minor leading to weak shoulder external rotation.
• deformity: bones of shoulder very prominent and obvious due to wasting deltoid. Shoulder may appear adducted and internally rotated.

Question 3

Name 4 common injuries affecting the axillary nerve

Answer 3

• Fracture surgical neck humerus
• stab wound to posterior shoulder
• anterior shoulder dislocation
• crutch palsy

Question 4

!!! Radial nerve palsy clinical features and deformity if upper injury at Axilla? (3)

Answer 4

Sensory
• numb skin over post arm, post forearm and radial distribution dorsum hand
Test in dorsal first web space

Motor
• weak elbow extension (posterior compartment arm paralysed - triceps)
• weak wrist extension, thumb extension and finger mcpj extension (posterior forearm compartment paralysed- brachioradialis, anconeus, supinator, extensor carpi radialis longus and brevis, extensor carpi ulnaris, extensor digitorum, extensor policis longus and brevis, extensor indicis, extensor digiti minimi, abductor policis longus)
• absent triceps and supinator reflexes! (Won’t work anyway in Acute trauma though)
Finger IPJ extension still possible thanks to lumbricals (median and ulnar nerves)

Deformity
• wrist drop
• inability to do shap sign
• In classical description- also forearm pronated, fingers flexed, thumb adducted

Question 5

Name 5 common injuries affecting radial nerve

Answer 5

• Fractures proximal humerus, shaft humerus or radius
• “Saturday night palsy” - patient fall asleep with arm hanging over back of chair
• “honeymoon palsy” - someone fall asleep with head on patient’s arm
• stab wounds to antecubital fossa, forearm or wrist
• excessively tight casts, wristbands, handcuffs
• prolonged tourniquet use on arm
Elbow dislocations and fractures

Question 6

!!! Median nerve palsy clinical features and deformity if upper damage at elbow? (3)

Answer 6

Sensory
• numb over thenar eminence!, and median distribution of hand (lat palm and lat 3.5 fingers palmar surface, tips dorsal lat 3 fingers)
Test at pulp index finger

Motor
• weak forearm pronation, wrist flexion and abduction, finger flexion (paralysis anterior compartment forearm except flexor carpi ulnaris and medial half of fdp so dipJ flexion at ring and little fingers preserved )
• paralysis thenar eminence: weak pincer grip and overall grip strength, weak thumb opposition.

Deformity
• hand of benediction: can’t flex index or middle fingers.
Opposition thumb and pinkie together
OK sign
Flat hand off table with thumb (abduction thumb)

Question 7

Name 4 common injuries affecting the median nerve

Answer 7

• Supracondylar fracture humerus
. Carpal tunnel syndrome
• stab wounds to antecubital fossa!, forearm or wrist
• deep wrist lacerations- self harm
Elbow dislocation

Question 8

!!! Ulnar nerve palsy clinical features and deformity if upper lesion at elbow? (3)

Answer 8

Sensory
• numb over hypothenar eminence!, and ulnar distribution of hand (medial 1/2 palm, dorsal medial 1,5 fingers and that area if dorsal hand, palmar medial 1,5 fingers)

Motor deficit
• weak wrist flexion and adduction (flexor carpi ulnaris)
• weak flexion ring and little finger dipJ (medial 2 parts fdp)
• weak mcpj flexion and IPJ extension of ring and little fingers, loss finger abduction and adduction, loss opposition little finger ( most intrinsic muscles except thenar and lat 2 lumbrical)

Deformity and tests
• claw hand: patient can’t extend IPJ of ring and little finger (same appearance as benediction but MCP hyperextended and IPJ flexed ) - not as bad as lower lesion
• Froment’s sign: hold paper between thumb and index finger . unable to adduct thumb and instead flex at IPj to hold paper (median nerve) = adductor pollicis palsy = ulnar n palsy
• Wartenberg’s sign: hand flat on surface pronated with digits extended and abduct. Ask pt to adduct fingers. Positive = inability to adduct 5th finger when extended

Question 9

Name 4 common injuries affecting the ulnar nerve

Answer 9

•Supracondylar fracture humerus
• fracture or soft tissue injuries to medial epicondyle humerus
• stab wound to forearm or wrist
• compression at cubital tunnel in elbow or Guyon’s ulnar Canal in wrist
Elbow #

Question 10

Common peroneal nerve palsy clinical signs and deformity? (3)

Answer 10

= common fibular nerve.

Sensory fallout:
• dorsum foot
• lateral side of leg

Motor fallout:
•dorsiflex foot at ankle joint (tibialis anterior)
• evert foot (fibularis longus and brevis)
• extend digits (extensor digitorum longus, extensor hallucis longus)

Deformity
• foot drop - plantarflexion

Question 11

Name 2 common mechanisms of common fibular nerve injury

Answer 11

Aka common peroneal nerve
• neck of fibula fracture
• tight plaster casts

Question 12

!!! Ulnar nerve palsy clinical features and deformity if lower lesion at wrist? (3)

Answer 12

Motor: intrinsic hand muscles affected only
• abduction and adduction fingers (interossei)
• weak flexion and extension ring and little finger due to paralysis medial 2 lumbricals and hypotherar muscles but median and radial nerve still work:
Flexor digitorum superficialis (PIPJ flex) (Median n), extensor digitorum (MCPJ IPJ ext), ext digiti minimi MCPJ (radial n)
• adduction thumb (adductor pollicis) (froment sign)

Sensory: dorsal and palmar cutaneous branch spared
• palmar side medial 1,5 fingers only (superficial branch)

Deformity and sign
• ulnar claw hand worse! Even though FDP spared
. Froment sign
• wartenberg sign

Question 13

!!! Median nerve palsy clinical features and deformity if lower damage at wrist? (3)

Answer 13

Motor intrinsic hand muscles
• weak thumb opposition, abduction and flexion (thenar muscles) - opponens pollicis, abductor pollicis brevis, flexor pollicis brevis
• weak flexion index and middle fingers (lateral 2 lumbricals)

Sensory: same as upper damage - lat 2/3 palm, palmar 3,5 fingers, dorsal fingertips lat 3,5
Test at volar pulp index finger

Deformity
NO hand of benediction
CAN do OK sign
Finger apposition not possible
Only can’t lift thumb from flat hand table (abduction)

Question 14

! Radial nerve palsy clinical features and deformity if upper damage in radial groove?

Answer 14

Sensory: superficial branch only, cutaneous branches to the arm and forearm already arisen.
• dorsal lateral 3,5 digits
. Dorsal 2/3 lateral hand
Test in dorsal first web space

Motor
• weak elbow extension (posterior compartment arm weak only - triceps long and lat heads not affected) (branches to long and lay heads triceps arise prox to radial groove)
• weak wrist extension, thumb extension and finger mcpj extension (posterior forearm compartment paralysed- brachioradialis, anconeus, supinator, extensor carpi radialis longus and brevis, extensor carpi ulnaris, extensor digitorum communis , extensor policis longus and brevis, extensor indicis, extensor digiti minimi, abductor policis longus)
Finger IPJ extension still possible thanks to lumbricals (median and ulnar nerves)

Deformity
• wrist drop
Can’t do shap sign
• In classical description- also forearm pronated, fingers flexed, thumb adducted

Question 15

! Radial nerve palsy clinical features. and deformity if injured in forearm? (AKA PIN lesion - Posterior interosseous nerve)

Answer 15

Sensory:superficial branch
• numb skin over radial distribution dorsum hand - lateral dorsal 3,5 digits and lateral 2/3 dorsal hand
Test in dorsal first web space

Motor: deep branch
• normal elbow extension
• weak, thumb extension and finger mcpj extension (posterior forearm compartment paralysed- brachioradialis, anconeus, supinator, extensor carpi radialis longus and brevis, extensor carpi ulnaris, extensor digitorum, extensor policis longus and brevis, extensor indicis, extensor digiti minimi, abductor policis longus)

• Flexor carpi radialis longus NOT affected so can still extend wrist, but will radial deviate

Finger IPJ extension still possible thanks to lumbricals (median and ulnar nerves)

Deformity
None! Because extensor carpi radialis longus unaffected!
Can’t do shap sign
NO wrist drop but radial deviation when extend wrist

Question 16

What is a pin lesion?

Answer 16

Lower radial nerve injury (post interosseous nerve)

Question 17

Describe the ulnar paradox

Answer 17

• Proximal ulnar nerve pathology closer to elbow = less severe claw hand deformity than distal lesion, though one would expect more severe deformity as more muscles are weakened
• instead, there will not be any flexion at the distal ip joints of the ring and little fingers due to paralysis of ulnar half of FDP, so will only have hyperextension at mcpj and flexion at pipJ

Question 18

How test sciatic nerve?

Answer 18

Innervate all muscles below the knee through tibial Nerve (posterior leg-calf, some intrinsic muscles of foot) and common fibular nerve (antenior and lat leg, remaining intrinsic foot muscles) and posterior thigh.
Thus test any foot movements.

Question 19

How test femoral nerve?

Answer 19

Supply anterior thigh. Hip flexors and knee extensor.
If injury, test with isometric contraction of the quads ( feel contraction with hand instead of asking patient to extend knee)

Question 20

How test common peroneal nerve?

Answer 20

AKA common fibular n
• Dorsiflex foot and extend digits (deep peroneal nerve-ant compartment leg)
• evert foot (superficial fibula Nerve - lateral compartment leg )

Question 21

Main differences between axillary, radial groove and wrist injury of radial nerve? (4)

Answer 21

Axilla
• wrist drop
• can't do thumbs up sign
• can t extend elbow
. All sensory affected

Radial groove
• wrist drop
• can’t do thumbs up sign
• weak extension elbow: only medial head of triceps is paralysed
. Sensory only superficial branch affected: dorsal lateral 3,5 digits, lateral 2/3 dorsum hand.
Lateral and posterior arm, middle and posterior forearm spared.

Wrist
• NORMAL wrist extension!
• can't do thumbs up sign
• NORMAL elbow extension!
• sensory superficial branch affected

Question 22

Major differences between upper and lower lesion of the median nerve? (5)

Answer 22

Upper
• all sensory branches affected
• hand of benediction when asked to close fist
• can't oppose thumb and pinkie
• can't do ok sign
• can't abduct thumb from flat palm

Lower
• all sensory branches affected
•NORMAL finger flexion thus no hand of benediction!
• can't oppose thumb and pinkie
. NORMAL ok sign!
• can't abduct thumb from flat palm

Question 23

Major differences between upper and lower lesion of the ulnar Nerve? (4 )

Answer 23

Upper
• all sensory innervation affected
• claw hand less severe! (Fdp doesn't work )
• Froment's sign
• wartenberg sign

Lower
• sensory dorsal branch spared, thus palmar side of medial 1,5 fingers affected only!
• claw hand more severe! (Flexion fdp)
• Froment's sign
• wartenberg sign

Question 24

Tibial nerve palsy clinical features?

Answer 24

Sensory
• posterolateral leg
• lateral foot
• sole foot

Motor
• posterior compartment leg
- superficial: plantaris, soleus (plantarflex), gastrocnemius (flex knee, plantarflex)
- deep: popliteus (lat rotate femur on tibia to unlock knee), flexor hallucis longis, flexor digitorum longis, tibialis posterior (inversion, plantarflex)
• most intrinsic foot muscles ( except extensor digitorum brevis- deep fibular nerve)

Deformity
. Loss plantarflex
• loss flex toes
• weak inversion (tibialis anterior can still help)