Download MBBS Anatomy PPT 17 Median Nerve And Its Injury Notes

Learning Objectives

1. Median nerve formation , root value and important

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relations

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

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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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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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Answer c

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.

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Which of the following nerve is likely to be involved?

A Ulnar nerve

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B Median nerve

C radial nerve

D Axil ary nerve

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Q 3 Injury to the median nerve in the arm would affect al of the following movements

except:

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A. Pronation of the forearm

B. Flexion of the wrist

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C. Flexion of the thumb

D. Supination of the forearm

Anatomy

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? Mixed nerve (contain motor & sensory fibers).

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

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? Runs in the median plane of the forearm , so

its called median nerve

MEDIAN NERVE

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? Formation:from two roots from

lateral cord

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[C(5),6,7]&

from medial cord(C8,T1) of

brachial plexus

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Before leaving axil a, C7 fibres

conveyed by median nerve are

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handed over to Ulnar nerve

? These two roots embrace the third

part of axillary artery uniting

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anterior or lateral to it
In the arm

? Closely related to the

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brachial artery through out

the course in arm

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? In the upper part it is

lateral to artey

? In the middle part it

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crosses the artery from

lateral to medial side

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? Remains on the medial

side up to elbow

Branches in arm

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

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elbow

In the cubital fossa

? Descends medial to

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brachial artery

? Posterior to bicipital

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aponeurosis

? Anterior to brachialis,

seperated by the

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muscle from the elbow

joint
? Leaves the cubital fossa by passing

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between two heads of pronator teres
In the forearm

? Enters the forearm between

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the heads of pronator teres

? Crosses the lateral side of

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ulnar artery from which it is

seperated by the deep head

of pronator teres

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? Gives branch to pronator

teres while passing between

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the two heads

? Proceeds behind a

tendinous ridge

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between the two heads

of Flexor digitorum

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superficialis and

anterior to Flexor

digitorum profundus

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? Here it is accompanied

by median artery, a

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branch of anterior

interosseous artery

? About 5 cm

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proximal to flexor

retinaculum it

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becomes

superficial

? Here it lies

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between the

tendon of

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palmaris longus

and the flexor

carpi radialis

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muscle

? Leaves the forearm and enters the palm of the

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hand by passing through the carpal tunnel deep to

flexor retinaculum
Branches in the forearm

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? Muscular branches

to all the muscles

in the

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superficial and

intermediate layer of

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forearm except one

(FCU) originate

medially from nerve

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just distal to elbow

joint

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? Anterior interosseous

nerve: originate between

two heads of pronator teres

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? passes distally down the

forearm with the anterior

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interosseous artery.

? Innervates the muscles of

deep layer (FPL, lateral half

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of FDP (for index and middle

finger) and pronator

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quadratus)

Articular Branches -supply

elbow,superior and inferior

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radio-ulnar joint, interosseous

membrane and wrist joint

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?Palmar cutaneous branch: starts just proximal to flexor

retinaculum

?Lateral branches - thenar skin and connecting branch to

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the lateral cutaneous nerve of fore arm

?Medial branches - central palmer skin and connecting

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branch to the palmar cutaneous branch of the ulnar nerve

? Communicating branch:

multiple

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

FDS and behind the ulnar artery

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to join the ulnar nerve
Median nerve in hand

? Proximal to flexor retinaculum it lies

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between the tendons of FCR & FDS

overlapped by palmaris longus

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? Distally it lies between the retinaculum and

the tendon in the retinaculum

? Site of compression

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? Distal to retinaculum nerve enlarges and

flattens

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? devides in to five or six branches

Branches in the hand

Lateral branch: gives

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Recurrent

muscular branch-

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short and

stout, curls upwards

over the distal border

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of flexor retinaculum

and FPL to supply

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three thenar muscles

APB, FPB &OP

? Three palmer digital

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branches- First two

supply the skin of the

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sides of the thumb ,its

web and distal part of

its dorsal surface.

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? Third supplies the skin

of the radial side of

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index finger and the

first lumbrical muscle

through its superficial

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surface
? Medial branch: gives

? Two common palmar digital

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branches- lateral and

medial which descend to

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the interdigital clefts

between the index, middle

and ring finger

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? Each nerve divides again

into two to supply adjacent

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sides of the fingers

? So in total it supplies skin of

lateral three and half fingers

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including the skin on the

dorsal aspect of terminal

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phalanges
Injuries

? High
? Low

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Median Nerve Lesion in Elbow Region ? High Lesion

? Damaged in

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supracondylar fracture

of humerus

? Muscles af ected are:

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? Pronator muscles of

the forearm

? All long flexors of

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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

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surface of the lateral 3?

fingers

? Trophic Changes:

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

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fingers

Median Nerve Lesion at Wrist

? Often injured by penetrating wounds (stab wounds or

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broken glass) of the forearm.

? Motor:

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? Thenar muscles are paralyzed and atrophy in time so thenar

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 .

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

region injuries

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Examination

? Flexor pol icis longus : Tested by holding

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thumb at its base and patient asked to flex the

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

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-pen held above the palm and the patient is

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

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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

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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

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Pope's blessing hand.

Benedict Sign
Kiloh-Nevin syndrome and OK Sign

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The Anterior Interosseus Nerve (AIN) syndrome

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

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nerve, or even dislocation of the elbow.

Kiloh-Nevin syndrome OK Sign

After history of stab wound on front of forearm , patient

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presents with impairment of the pincer movement and is having

difficulty picking up a small item, such as a coin, from a flat

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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

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C Injury to ulnar nerve

D. Injury to median nerve at level of wrist

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Ape hand deformity

In "Ape hand deformity", the thenar muscles become

paralyzed due to impingement and are subsequently flattened.

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

the adductor pollicis remains intact, the flattening of the

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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.

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Ape Thumb

Median nerve Compression

Syndromes

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? Carpal Tunnel ?nerve may be compressed due to

inflammatory condition of ulnar bursa or anterior

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dislocation of lunate bone

? Pronator
? Interosseous

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Carpal Tunnel Syndrome

? Compressive neuropathy as the nerve passes through the

Carpal Tunnel

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? Causes:

- Idiopathic

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: Most common

- Inflammatory : Rheumatoid Arthritis

: Wrist osteoarthritis

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- Post traumatic : Bone thickening

- Endocrine

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: Myxoedema

: Acromegaly

- Pregnancy

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- Gout

- Repetitive wrist movts: Typists & Computer users

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Carpal Tunnel Syndrome

? The commonest neurological

problem associated with median

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nerve is compression beneath

flexor retinaculum at wrist.

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? Motor: Weak motor function of

thumb, index & middle finger

? Sensory: Burning pain or `pins

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and needles' along distribution

of median nerve to lateral 3?

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fingers

No sensory changes over palm as palmer cutaneous branch

is given before median nerve enters carpal tunnel.

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Symptoms

? Hand and wrist Pain

? Paraesthesia

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? Hypoaesthsia

? Sparing of Palmar cutaneous branch supply

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? Patient wakes at night with burning or aching

pain and shakes the hand to obtain relief and

restore sensation

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? Aggravated by elevation of hand

? Thenar atrophy and weakness of thumb

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opposition and abduction may develop late

Diagnosis

? History

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? Clinical examination:

- Thenar wasting

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- Phalen's sign

- Tinel's sign

- Carpal compression test

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? Electro Diagnostic Studies:

- Very reliable for evaluation

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- Atypical cases may be present

Thenar atrophy

Phalen test

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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.

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

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reproduce the symptoms of carpal tunnel syndrome.


Tinel's Sign

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Carpal Compression test/ Durkan's test
Pronator teres syndrome

? High Compression neuropathy

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? It is rare compared to CTS and AIS
Pronator teres syndrome

The characteristic physical finding is tenderness over the

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proximal median nerve, which is aggravated by resisted

pronation of the forearm.

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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.

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

as in the palm, indicating impairment of the median nerve

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proximal to the flexor retinaculum.

Symptoms & signs

? Symptoms are similar to those of carpal tunnel syndrome

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? Sensory disturbances

- Thumb & Index > Middle finger

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? Night pain is unusual and forearm pain is more common

? Hand numbness on gripping

? Phalen's test negative

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? 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 (

pronator tension )

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