Download MBBS Anatomy PPT 96 Median Nerve And Its Lesions Notes

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Median Nerve and its Lesions

Dr Mukesh Singla

Learning Objectives

1. Median nerve formation , root value and important

relations

2. Motor and sensory supply

3. Important sites of injuries/entrapment of nerve

4. Effects of injury of median nerve

5. How to clinically test median nerve injury
MCQ

Q 1.Regarding the median nerve, all are correct

EXCEPT:

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

brachial plexus.

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

coracobrachialis.

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

artery.

d. It enters the hand in the carpal tunnel.

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

MCQ

Q 1.Regarding the median nerve, all are correct

EXCEPT:

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

brachial plexus.

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

coracobrachialis.

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

artery.

d. It enters the hand in the carpal tunnel.

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

Answer c
MCQ

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

thenar eminence. Which of the following nerve is likely

to be involved?

A Ulnar nerve

B Median nerve

C radial nerve

D Axillary nerve

MCQ

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

all of the following movements except:

A. Pronation of the forearm

B. Flexion of the wrist

C. Flexion of the thumb

D. Supination of the forearm
Anatomy

? Mixed nerve (contain motor & sensory fibers).

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

? Runs in the median plane of the forearm , so

its called median nerve

MEDIAN NERVE

? Formation:from two roots from

lateral cord

[C(5),6,7]&

from medial cord(C8,T1) of

brachial plexus

Before leaving axil a, C7 fibres

conveyed by median nerve are

handed over to Ulnar nerve

? These two roots embrace the third

part of axillary artery uniting

anterior or lateral to it


In the arm

? Closely related to the

brachial artery through out

the course in arm

? In the upper part it is

lateral to artey

? In the middle part it

crosses the artery from

lateral to medial side

? Remains on the medial

side up to elbow
Branches in arm

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

elbow
In the cubital fossa

? Descends medial to

brachial artery

? Posterior to bicipital

aponeurosis

? Anterior to brachialis,

seperated by the

muscle from the elbow

joint

? Leaves the cubital fossa by passing

between two heads of pronator teres
In the forearm

? Enters the forearm between

the heads of pronator teres

? Crosses the lateral side of

ulnar artery from which it is

seperated by the deep head

of pronator teres

? Gives branch to pronator

teres while passing between

the two heads

? Proceeds behind a

tendinous ridge

between the two heads

of Flexor digitorum

superficialis and

anterior to Flexor

digitorum profundus

? Here it is accompanied

by median artery, a

branch of anterior

interosseous artery
? About 5 cm

proximal to flexor

retinaculum it

becomes

superficial

? Here it lies

between the

tendon of

palmaris longus

and the flexor

carpi radialis

muscle

? Leaves the forearm and enters the palm of the

hand by passing through the carpal tunnel deep to

flexor retinaculum
Branches in the forearm

? Muscular branches

to all the muscles

in the

superficial and

intermediate layer of

forearm except one

(FCU) originate

medially from nerve

just distal to elbow

joint

? Anterior interosseous

nerve: originate between

two heads of pronator teres

? passes distally down the

forearm with the anterior

interosseous artery.

? Innervates the muscles of

deep layer (FPL, lateral half

of FDP (for index and middle

finger) and pronator

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

retinaculum

?Lateral branches - thenar skin and connecting branch to

the lateral cutaneous nerve of fore arm

?Medial branches - central palmer skin and connecting

branch to the palmar cutaneous branch of the ulnar nerve

? Communicating branch:

multiple

?Arise in the proximal forearm
? Pass medialy between FDP &

FDS and behind the ulnar artery

to join the ulnar nerve
Median nerve in hand

? Proximal to flexor retinaculum it lies

between the tendons of FCR & FDS

overlapped by palmaris longus

? Distally it lies between the retinaculum and

the tendon in the retinaculum

? Site of compression

? Distal to retinaculum nerve enlarges and

flattens

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

Lateral branch: gives

Recurrent

muscular branch-

short and

stout, curls upwards

over the distal border

of flexor retinaculum

and FPL to supply

three thenar muscles

APB, FPB &OP

? Three palmer digital

branches- First two

supply the skin of the

sides of the thumb ,its

web and distal part of

its dorsal surface.

? Third supplies the skin

of the radial side of

index finger and the

first lumbrical muscle

through its superficial

surface
? Medial branch: gives

? Two common palmar digital

branches- lateral and

medial which descend to

the interdigital clefts

between the index, middle

and ring finger

? Each nerve divides again

into two to supply adjacent

sides of the fingers

? So in total it supplies skin of

lateral three and half fingers

including the skin on the

dorsal aspect of terminal

phalanges
Injuries

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

? Damaged in

supracondylar fracture

of humerus

? Muscles af ected are:
? Pronator muscles of

the forearm

? All long flexors of

wrist and fingers

except FCU and

medial half of FDP

Motor Effects:

Wasting

of thenar

? Loss of pronation. Hand is kept in

eminence

supine position

? Wrist shows weak flexion, and

ulnar deviation

? Loss of flexion on interphalangeal

joints of the index and middle

fingers

? Weak flexion of ring and little

finger

Ulnar deviation

? Thumb is adducted and lateral y

rotated, with loss of flexion of

terminal phalanx and loss of

opposition

? Wasting of thenar eminence

? Hand looks flat ened and

"apelike", and presents an inability

to flex three most radial digits

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

sensation from:

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

3? fingers

? Distal part of the dorsal

surface of the lateral 3?

fingers

? Trophic Changes:

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

fingers

Median Nerve Lesion at Wrist

? Often injured by penetrating wounds (stab wounds or

broken glass) of the forearm.

? Motor:

? Thenar muscles are paralyzed and atrophy in time so thenar

eminence becomes flattened

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

lateral two fingers are arrested in adduction & hyperextension

position .

? "Apelike hand"
? Sensory & trophic changes are same as in elbow

region injuries


Examination

? Flexor pol icis longus : Tested by holding

thumb at its base and patient asked to flex the

terminal phalanx


Examination

? Flexor digitorum superficialis & profundus

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

finger of af ected side fails to flex

Examination

? Flexor Carpi radialis : Hand deviates to the

ulnar side when flexed against resistance
Examination

? 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

asked to touch the pen with his thumb

Examination

? opponens pol icis : brings the tip of the

thumb towards the tips of other fingers
Opponens pollices

Benedict Sign

Lesion to upper arm area, just proximal to where motor

branches of forearm flexors originate, is diagnosed if the

patient is unable to make a fist.

More specifically, the patient's index and middle finger

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.
Benedict Sign

Kiloh-Nevin syndrome and OK Sign

The Anterior Interosseus Nerve (AIN) syndrome

Patients suffering from this syndrome have impaired distal

interphalangeal joint, because of which they are unable to

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.
Kiloh-Nevin syndrome OK Sign

MCQ

After history of stab wound on front of forearm ,

patient presents with impairment of the pincer

movement and is having difficulty picking up a small

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

B injury to main median nerve as pincer movement

involves FDS

C Injury to ulnar nerve

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

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

the adductor pollicis remains intact, the flattening of the

muscles causes the thumb to become adducted and laterally

rotated. The opponens pollicis causes the thumb to flex and

rotate medially, leaving the thumb unable to oppose.

Ape Thumb
Median nerve Compression

Syndromes

? Carpal Tunnel ?nerve may be compressed due to

inflammatory condition of ulnar bursa or anterior

dislocation of lunate bone

? Pronator
? Interosseous

Carpal Tunnel Syndrome

? Compressive neuropathy as the nerve passes through the

Carpal Tunnel

? Causes:

- Idiopathic

: Most common

- Inflammatory : Rheumatoid Arthritis

: Wrist osteoarthritis

- Post traumatic : Bone thickening

- Endocrine

: Myxoedema

: Acromegaly

- Pregnancy

- Gout

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

? The commonest neurological

problem associated with median

nerve is compression beneath

flexor retinaculum at wrist.

? Motor: Weak motor function of

thumb, index & middle finger

? Sensory: Burning pain or `pins

and needles' along distribution

of median nerve to lateral 3?

fingers

No sensory changes over palm as palmer cutaneous branch

is given before median nerve enters carpal tunnel.

Symptoms

? Hand and wrist Pain

? Paraesthesia

? Hypoaesthsia

? Sparing of Palmar cutaneous branch supply

? Patient wakes at night with burning or aching

pain and shakes the hand to obtain relief and

restore sensation

? Aggravated by elevation of hand

? Thenar atrophy and weakness of thumb

opposition and abduction may develop late
Diagnosis

? History

? Clinical examination:

- Thenar wasting

- Phalen's sign

- Tinel's sign

- Carpal compression test

? Electro Diagnostic Studies:

- Very reliable for evaluation

- Atypical cases may be present

Thenar atrophy
Phalen test

A positive Phalen test is highly suggestive of carpal tunnel

syndrome.

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

complete unforced flexion for at least 30 seconds.

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

reproduce the symptoms of carpal tunnel syndrome.


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

Pronator teres syndrome

? High Compression neuropathy

? It is rare compared to CTS and AIS

Pronator teres syndrome

The characteristic physical finding is tenderness over the

proximal median nerve, which is aggravated by resisted

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

involvement of the anterior interosseous nerve.

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

as in the palm, indicating impairment of the median nerve

proximal to the flexor retinaculum.
Symptoms & signs

? Symptoms are similar to those of carpal tunnel syndrome

? Sensory disturbances

- Thumb & Index > Middle finger

? Night pain is unusual and forearm pain is more common

? Hand numbness on gripping

? Phalen's test negative

? Double crush phenomena

? Symptoms provoked by resisted elbow flexion with forearm

supinated ( tightening of bicipital aponeurosis )

? By resisted forearm pronation with the elbow extended (

pronator tension )
Thank You

This post was last modified on 05 April 2022