Download MBBS Anatomy PPT 96 Median Nerve And Its Lesions Notes

Median Nerve and its Lesions

Dr Mukesh Singla

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Learning Objectives

1. Median nerve formation , root value and important

relations

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2. Motor and sensory supply

3. Important sites of injuries/entrapment of nerve

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4. Effects of injury of median nerve

5. How to clinically test median nerve injury
MCQ

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Q 1.Regarding the median nerve, all are correct

EXCEPT:

a. Arises from both the medial and lateral cords of the

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brachial plexus.

b. It crosses the brachial artery at the insertion of the

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coracobrachialis.

c. In the cubital fossa, it lies lateral to the brachial

artery.

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d. It enters the hand in the carpal tunnel.

e. Injury of the nerve causes ape-like hand.

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MCQ

Q 1.Regarding the median nerve, all are correct

EXCEPT:

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a. Arises from both the medial and lateral cords of the

brachial plexus.

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b. It crosses the brachial artery at the insertion of the

coracobrachialis.

c. In the cubital fossa, it lies lateral to the brachial

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artery.

d. It enters the hand in the carpal tunnel.

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e. Injury of the nerve causes ape-like hand.

Answer c
MCQ

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Q 2. A 40 year tailor complains of pain numbness and

weakness of right hand for last 3 months. On

examination, there is hypoesthesia and atrophy of

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thenar eminence. Which of the following nerve is likely

to be involved?

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A Ulnar nerve

B Median nerve

C radial nerve

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D Axillary nerve

MCQ

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Q 3 Injury to the median nerve in the arm would affect

all of the following movements except:

A. Pronation of the forearm

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B. Flexion of the wrist

C. Flexion of the thumb

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D. Supination of the forearm
Anatomy

? Mixed nerve (contain motor & sensory fibers).

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? Root value: C 5,6,7,8 & T1

? Runs in the median plane of the forearm , so

its called median nerve

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MEDIAN NERVE

? Formation:from two roots from

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lateral cord

[C(5),6,7]&

from medial cord(C8,T1) of

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brachial plexus

Before leaving axil a, C7 fibres

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conveyed by median nerve are

handed over to Ulnar nerve

? These two roots embrace the third

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part of axillary artery uniting

anterior or lateral to it

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In the arm

? Closely related to the

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brachial artery through out

the course in arm

? In the upper part it is

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lateral to artey

? In the middle part it

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crosses the artery from

lateral to medial side

? Remains on the medial

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side up to elbow
Branches in arm

? Branch to Pronator Teres just above elbow

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? Branch to brachial artery
? Branch to elbow joint at or just below the

elbow
In the cubital fossa

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? Descends medial to

brachial artery

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? Posterior to bicipital

aponeurosis

? Anterior to brachialis,

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seperated by the

muscle from the elbow

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joint

? Leaves the cubital fossa by passing

between two heads of pronator teres

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In the forearm

? Enters the forearm between

the heads of pronator teres

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? Crosses the lateral side of

ulnar artery from which it is

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seperated by the deep head

of pronator teres

? Gives branch to pronator

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teres while passing between

the two heads

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? Proceeds behind a

tendinous ridge

between the two heads

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of Flexor digitorum

superficialis and

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anterior to Flexor

digitorum profundus

? Here it is accompanied

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by median artery, a

branch of anterior

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interosseous artery
? About 5 cm

proximal to flexor

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retinaculum it

becomes

superficial

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? Here it lies

between the

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tendon of

palmaris longus

and the flexor

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carpi radialis

muscle

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? Leaves the forearm and enters the palm of the

hand by passing through the carpal tunnel deep to

flexor retinaculum

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Branches in the forearm

? Muscular branches

to all the muscles

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in the

superficial and

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intermediate layer of

forearm except one

(FCU) originate

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medially from nerve

just distal to elbow

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joint

? Anterior interosseous

nerve: originate between

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two heads of pronator teres

? passes distally down the

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forearm with the anterior

interosseous artery.

? Innervates the muscles of

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deep layer (FPL, lateral half

of FDP (for index and middle

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finger) and pronator

quadratus)
?Palmar cutaneous branch: starts just proximal to flexor

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retinaculum

?Lateral branches - thenar skin and connecting branch to

the lateral cutaneous nerve of fore arm

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?Medial branches - central palmer skin and connecting

branch to the palmar cutaneous branch of the ulnar nerve

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? Communicating branch:

multiple

?Arise in the proximal forearm

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? Pass medialy between FDP &

FDS and behind the ulnar artery

to join the ulnar nerve

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Median nerve in hand

? Proximal to flexor retinaculum it lies

between the tendons of FCR & FDS

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overlapped by palmaris longus

? Distally it lies between the retinaculum and

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the tendon in the retinaculum

? Site of compression

? Distal to retinaculum nerve enlarges and

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flattens

? devides in to five or six branches
Branches in the hand

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Lateral branch: gives

Recurrent

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muscular branch-

short and

stout, curls upwards

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over the distal border

of flexor retinaculum

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and FPL to supply

three thenar muscles

APB, FPB &OP

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? Three palmer digital

branches- First two

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supply the skin of the

sides of the thumb ,its

web and distal part of

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its dorsal surface.

? Third supplies the skin

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of the radial side of

index finger and the

first lumbrical muscle

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through its superficial

surface
? Medial branch: gives

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? Two common palmar digital

branches- lateral and

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medial which descend to

the interdigital clefts

between the index, middle

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and ring finger

? Each nerve divides again

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into two to supply adjacent

sides of the fingers

? So in total it supplies skin of

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lateral three and half fingers

including the skin on the

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dorsal aspect of terminal

phalanges
Injuries

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? High
? Low
Median Nerve Lesion in Elbow Region ? High Lesion

? Damaged in

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supracondylar fracture

of humerus

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? Muscles af ected are:
? Pronator muscles of

the forearm

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? All long flexors of

wrist and fingers

except FCU and

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medial half of FDP

Motor Effects:

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Wasting

of thenar

? Loss of pronation. Hand is kept in

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eminence

supine position

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? Wrist shows weak flexion, and

ulnar deviation

? Loss of flexion on interphalangeal

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joints of the index and middle

fingers

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? Weak flexion of ring and little

finger

Ulnar deviation

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? Thumb is adducted and lateral y

rotated, with loss of flexion of

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terminal phalanx and loss of

opposition

? Wasting of thenar eminence

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? Hand looks flat ened and

"apelike", and presents an inability

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to flex three most radial digits

when asked to make a fist.
? Sensory Ef ects: Loss of

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sensation from:

? The radial side of the palm
? Palmar aspect of the lateral

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3? fingers

? Distal part of the dorsal

surface of the lateral 3?

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fingers

? Trophic Changes:

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? Dry and scaly skin
? Easily cracking nails
? Atrophy of the pulp of

fingers

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Median Nerve Lesion at Wrist

? Often injured by penetrating wounds (stab wounds or

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broken glass) of the forearm.

? Motor:

? Thenar muscles are paralyzed and atrophy in time so thenar

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eminence becomes flattened

? Opposition & abduction of thumb are lost, and thumb and

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lateral two fingers are arrested in adduction & hyperextension

position .

? "Apelike hand"

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? Sensory & trophic changes are same as in elbow

region injuries

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Examination

? Flexor pol icis longus : Tested by holding

thumb at its base and patient asked to flex the

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terminal phalanx


Examination

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? Flexor digitorum superficialis & profundus

(Ochsner's clasping test)
- Patient is asked to clasp the hands , the index

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finger of af ected side fails to flex

Examination

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? Flexor Carpi radialis : Hand deviates to the

ulnar side when flexed against resistance
Examination

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? Muscles of Thenar eminance:

-abductor pol icis brevis (Pen test)
- hand laid flat on the table
-pen held above the palm and the patient is

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asked to touch the pen with his thumb

Examination

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? opponens pol icis : brings the tip of the

thumb towards the tips of other fingers
Opponens pollices

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Benedict Sign

Lesion to upper arm area, just proximal to where motor

branches of forearm flexors originate, is diagnosed if the

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patient is unable to make a fist.

More specifically, the patient's index and middle finger

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cannot flex at the MCP joint, while the thumb usually is

unable to oppose. This is known as hand of benediction or

Pope's blessing hand.

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Benedict Sign

Kiloh-Nevin syndrome and OK Sign

The Anterior Interosseus Nerve (AIN) syndrome

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Patients suffering from this syndrome have impaired distal

interphalangeal joint, because of which they are unable to

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pinch anything or make and "OK" sign with their index finger

and thumb. The syndrome can either happen from pinched

nerve, or even dislocation of the elbow.

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Kiloh-Nevin syndrome OK Sign

MCQ

After history of stab wound on front of forearm ,

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patient presents with impairment of the pincer

movement and is having difficulty picking up a small

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item, such as a coin, from a flat surface. Which of the

following statement is correct ?

A Injury to anterior interroseous nerve of median nerve

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B injury to main median nerve as pincer movement

involves FDS

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C Injury to ulnar nerve

D. Injury to median nerve at level of wrist
Ape hand deformity

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In "Ape hand deformity", the thenar muscles become

paralyzed due to impingement and are subsequently flattened.

it is seen only after the thenar muscles have atrophied. While

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the adductor pollicis remains intact, the flattening of the

muscles causes the thumb to become adducted and laterally

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rotated. The opponens pollicis causes the thumb to flex and

rotate medially, leaving the thumb unable to oppose.

Ape Thumb

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Median nerve Compression

Syndromes

? Carpal Tunnel ?nerve may be compressed due to

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inflammatory condition of ulnar bursa or anterior

dislocation of lunate bone

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? Pronator
? Interosseous

Carpal Tunnel Syndrome

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? Compressive neuropathy as the nerve passes through the

Carpal Tunnel

? Causes:

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- Idiopathic

: Most common

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- Inflammatory : Rheumatoid Arthritis

: Wrist osteoarthritis

- Post traumatic : Bone thickening

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- Endocrine

: Myxoedema

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: Acromegaly

- Pregnancy

- Gout

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- Repetitive wrist movts: Typists & Computer users
Carpal Tunnel Syndrome

? The commonest neurological

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problem associated with median

nerve is compression beneath

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flexor retinaculum at wrist.

? Motor: Weak motor function of

thumb, index & middle finger

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? Sensory: Burning pain or `pins

and needles' along distribution

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of median nerve to lateral 3?

fingers

No sensory changes over palm as palmer cutaneous branch

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is given before median nerve enters carpal tunnel.

Symptoms

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? Hand and wrist Pain

? Paraesthesia

? Hypoaesthsia

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? Sparing of Palmar cutaneous branch supply

? Patient wakes at night with burning or aching

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pain and shakes the hand to obtain relief and

restore sensation

? Aggravated by elevation of hand

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? Thenar atrophy and weakness of thumb

opposition and abduction may develop late
Diagnosis

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? History

? Clinical examination:

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- Thenar wasting

- Phalen's sign

- Tinel's sign

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- Carpal compression test

? Electro Diagnostic Studies:

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- Very reliable for evaluation

- Atypical cases may be present

Thenar atrophy

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Phalen test

A positive Phalen test is highly suggestive of carpal tunnel

syndrome.

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Phalen's test is performed by having patients place their wrists in

complete unforced flexion for at least 30 seconds.

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If the median nerve is entrapped at the wrist, this maneuver will

reproduce the symptoms of carpal tunnel syndrome.

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Tinel's Sign
Carpal Compression test/ Durkan's test

Pronator teres syndrome

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? High Compression neuropathy

? It is rare compared to CTS and AIS

Pronator teres syndrome

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The characteristic physical finding is tenderness over the

proximal median nerve, which is aggravated by resisted

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pronation of the forearm.

The flexor pol icis longus and FDP of the index finger are weak,

leading to impairment of the pincer movement. This reflects

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involvement of the anterior interosseous nerve.

Sensory changes may be found in the first three fingers as well

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as in the palm, indicating impairment of the median nerve

proximal to the flexor retinaculum.
Symptoms & signs

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? Symptoms are similar to those of carpal tunnel syndrome

? Sensory disturbances

- Thumb & Index > Middle finger

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? Night pain is unusual and forearm pain is more common

? Hand numbness on gripping

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? Phalen's test negative

? Double crush phenomena

? Symptoms provoked by resisted elbow flexion with forearm

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supinated ( tightening of bicipital aponeurosis )

? By resisted forearm pronation with the elbow extended (

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pronator tension )
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