Peripheral Nerve Injuries

Question 1

What is a structure of a peripheral nerve

Answer 1

A individual nerve is covered by outermost epineurium.
A number of fascicular is found within aipineurium which inturn is covered by perineurium.
Each fascicular contain a bundle of nerve fibres which is enclosed in a collagen connective tissue known as endoneurium. Each action cylinder have a neurilemma tube

Question 2

Nerve degeneration

Answer 2

Proximal part undergoes primary or retrograde degeneration.

Distal part undergoes secondary or Wallerian degeneration.

Question 3

Nerve regeneration

Answer 3

Rate of recovery is 1 mm per day that is 1 inch per month.
Nerve regeneration can be clinically assessed by tinel sign.
On generally tapping on nerve along its course from distal to proximal sensation can be felt at the area of skin supplied by the nerve. A distal progression of the level at which it occurs suggest regeneration.
Tinels progression or recovery of nerve occur from proximal to distal direction.

Question 4

Classification of nerve injuries

Answer 4

Seddon’s classification and Sunderland classification.

Question 5

Seddon’s classification

Answer 5

Nerve injuries are of three types- neuroprexia, axonotmesis & neurotmesis.

1. Neuroprexia- physiological disruption of conduction in nerve fibre. No structural changes occur. Recovery spondaneous and complete.
2. Axonotmesis- action sir damaged but internal structure of nervous preserved. Valerian degeneration occurs. Recovery is spontaneous but may take many month, complete recovery may not occur. Injury of endoneurium may or may not occur.
3. Neurotmesis- the structure of an hour is damaged by actual cutting or scaring of segment. Valerian degeneration occurs. Spontaneous recovery is not possible now repair is required.

Question 6

Sunderland classification

Answer 6

Six types of nerve injuries are present.
Type 1 neuropraxia.
Type 2 and 3 axonotmesis with or without endoneurium injury
Type 4 combination of 1and 2.
Type 5 neurotmesis.
Type 6 combination of the above.

Question 7

Course of radial nerve

Answer 7

*Arise from posterior cord of brachial plexus.
*In the axilla- lies behind the third part of axillary artery. Give of three branches: posterior cutaneous nerve of arm, now to long head of triceps, love to middle head of triceps.
*In the arm- Enter the arm at the lower border of teres major and between the long and middle head of triceps to enter the lower triangular space and then reaches spiral Groove along with the profunda brachi artery.
It gives a five branches here- lower lateral cutaneous nerve of arm, posterior cutaneous nerve of forearm, nerve to lateral head of triceps, nerve to medial head of triceps, nerve to anconeus.
At the lower end of the spiral groove radial nerve pierces lateral muscular septum of the arm and reaches the anterior compartment of the arm and at first each lies between brachialis and brachioradialis and then between brachialis and extensive carpi radialis longes and gives of these respective branches above the lateral epicondyle.
At the level of lateral epicondyle of humerus it terminates by dividing Indo superficial and deep branches in the lateral part of cubital fossa. The deep branch supplies extensive carpi radialis bravis and supinator.
After supplying ,it passes through substance of supinator and enter the posterior compartment of forearm and supplies all the extensive muscles of forearm.
The superficial branch is sensory . It terminates has cutaneous branches which provides sensory innervation to skin over lateral part of the dorsum of hand and dorsal surface of lateral 3 and the half digits proximal to the nail beds.

Question 8

Course of median nerve

Answer 8

It arises from lateral root of lateral cord and medial root of medial cord of Brachial plexus.
*In the axilla- made in a life lateral to the third part of axillary artery.
*In the arm- lies lateral to brachial artery then it crosses in front of the artery from lateral to medial side at the level of mid humerus after crossing it runs downward to enter the cubital fossa.
*In the cubital fossa- nerve life medial to brachial artery and tender of biceps brachii. Anteriorly bicipital aponeurosis and posteriorly brachialis muscle. It gives muscular branches from its medial side to supply or superficial flexors of fore arm (flexor carpi radialis ,palmeris longus and flexor digitorum superficialis).
Median nerve leaves cubital fossa by passing between the two heads of pronator teres. At this point it gives of anterior interossious nerve. It is purely motor and it supplies two and a half muscles muscles (FPL, lateral half of FDP, Pronator quadratus)
*In the forearm- median nerve passes downwards behind the two heads of flexor digital superficialis and run deep to flexor digital superficialis. About 5 cm proximal to flexor retinaculam median nerve emergence from the lateral side of FDS and becomes superficial lying lateral to the tendons of FDS and posterior to the tendon of PL.
*In the mid arm-it gives muscular branches to radial head of flexor digitorum superficialis which give rise to tendon for index finger.
Before entering carpal tunnel it gives of flexor cutaneous branch which passes superficial to flexor retinaculam to supply the skin over thenar eminence and lateral part of the palm.

Median nerve enter the palm by passing through carpal tunnel where it lies deep to flexor retinaculam and superficial to tendency of fds, fdp and fpl and the associated ulnar and radial bursae.
*In the palm- nerve flattens at the distal border of flexor retinakulam and divides into lateral and medial divisions. Lateral division give a recurrent branch which curves upward to supply Thenar muscles except The Deep head of FPB.
Lateral division divide Sindhu 3 power branches where is medial division give some two farmer digital nerves.
The 5 palmar digital nerves supply-sensory innervation to the skin of palmar aspect of lateral 3 and half digits including nail bed and skin. First and second lumbricals.

Question 9

Wrist drop

Answer 9

Due to weakness of dorsiflexors wrist remain in palmar flexion.
Seen in radial nerve palsy

Question 10

Foot drop

Answer 10

Due to weakness in dorsiflexers foot remains in plantar flexion.
Occur in common peronal nerve palsy.

Question 11

Winging of scapula

Answer 11

Vertebral border of scapula becomes prominent when patient tries to push against a wall.
Paralysis of serratus anterior muscle in long thoracic nerve palsy.

Question 12

Claw hand

Answer 12

Hyperextension of metacarpo phalangeal and flexion of distal and proximal inter phalangeal joint.
Due to paralysis of lumbricals
Medial two fingers in ulnar nerve palsy and all the four fingers developed clawing in combined median and ulnar nerve palsy.

Question 13

Ape thumb deformity

Answer 13

Thumb is in the same plane as the wrist.
Occur due to paralysis of opponens pollicis muscle
And median nerve palsy

Question 14

Pointing index

Answer 14

On asking the patient to make a fist it is noticed that the index finger remains straight.
Due to paralysis of flexors(FDS and lateral FDP) of index finger which occur in median nerve palsy at level proximal to the elbow.

Question 15

Policeman tip deformity

Answer 15

ARM will be addicted and internally rotated and Hands by the side of the body with elbow extended and fore arm fully pronated.
Because of paralysis of abductor and external rotaters of the shoulder and flexes and supinators of the elbow. Seen in Erb’s palsy

Question 16

Pen test 🖊️

Answer 16

A pen is held about the thumb and the patient is asked to test the pen with the tip of his thumb to check for abductor pollicis brevis . This is called as pen test .
Muscle is supplied by median nerve

Question 17

What is egawa test

Answer 17

This is for dorsal interossei of middle finger
With the hand kept flat on a table palmer surface down the patient is asked to more his middle finger sideways. This test ulnar nerve.

Question 18

What is card test

Answer 18

This is for palmar interossei of fingers.
The examiner inserts a card between the two extended fingers and the patient is asked to hold tightly as possible while the external tries to pull the card out. Power of adductors can be judged.

Question 19

How to test for the power of first dorsal interossious muscle

Answer 19

By asking the patient to abduct the index finger against resistance.

Question 20

What is Froment’s sign

Answer 20

• Normally if a patient is asked to gras the book between the thumb and index finger the term will be extended (adductor pollicis and first dorsal interossious muscle)
• If the ulnar nerve is injured adductor pollicis will be paralysed and the patient will hold the book by using flexor pollicis longus. This produces flexion at the interphalangeal joint of the thumb. *More prominent if the examiner tries to put the book out.

Question 21

What is tinel’s sign

Answer 21

On gently taping over the nerve along its course from distal to proximal a pin and needle sensation is felt in the area of skin supplied by the nerve. Distal progression of the level at which it occurs suggest regeneration.

Question 22

Primary nerve repair indication

Answer 22

Indicated when the nerve is cut by a sharp object and the patient reports early.
Need experience in the use of fine sutures and operative microscope for this kind of surgery.

Question 23

Delayed primary repair

Answer 23

Indicated when the wound is contaminated.
First stage the wound is debrided and the two nerve ends are approximated with one or two fine silk sutures to prevent the retraction of cut end.
After 2 week once the wound heals a definitive repair is done.

Question 24

Secondary repair indication

Answer 24

1. Nerve lesion presenting sometime after injury
2. Syndrome of incomplete interruption
3. Syndrome of irritation
4. Failure of conservative treatment

Question 25

Techniques of nerve repair

Answer 25

Nerve suture

Nerve grafting

Question 26

Nerve suture techniques

Answer 26

Epineural suture
Epi perineural suture
Perineural suture
Group fascicular suture

Question 27

Measures adopted to gain length and achieve end to end suture

Answer 27

1. Mobilization of nerve both sides
2. Relaxation of nerves by temporary positioning the joints in favourable position.
3. Alteration of course of never
4. Stripping the branches from parent nerve without tearing them
5. Sacrificing some and important branch if it is hampering nerve mobilization

Question 28

Nerve grafting indication

Answer 28

1. When the nerve gap is more than 10 cm

2. End to end suture is likely to result in tension at the suture line.

Question 29

What is done in nerve grafting

Answer 29

An expandable nerve is taken and future between the two ends of original nerve.