Peripheral nerve injury - Neurosurgery (NS)

Question 1

Which part in axon cut undergoes Wallerian dengeneration?

Answer 1

Distal to the cut
(Regeneration from proximal to distal, 1mm per day)

Question 2

Nerve injuries Etiology

Answer 2

1- Open injuries: open wounds, crushes, gun shots, lacerations and burns.
2- Closed injuries: contusion, traction, compression, ischemia or accidental injection of irritant material in the nerve.

Question 3

Pathology of Nerve injury types

Answer 3

1- Neuropraxia: The nerve with all its axons and nerve coverings are anatomically intact but there is functional loss. It may be due to minor compression or traction on the nerve.
● There is complete paralysis by the muscles supplied by the nerve.
● There is no sensory loss or there is patchy sensory loss.
● Recovery is usually complete within days or weeks.
2- Axonotmesis: is partial or complete loss of continuity of the axon with intact neurolemmal sheath.
● It occurs due to contusion and traction of the nerve.
● Axonal Wallerian degeneration occurs distal to the site of injury.
● Complete regeneration of the nerve is complete through the intact neurolemmal tube with complete functional recovery.
3- Neurotmesis: is partial or complete division of the nerve and its sheath.
* Wallerain degeneration occurs distal to the site of injury
* End neuroma is formed. Side neuroma occurs in partial nerve injuries
* Recovery will never occur without nerve repair

Question 4

Clinical features of nerve injury

Answer 4

1- Motor defects:
● Paralysis of the muscle group supplied by the injured nerve resulting in apparent deformity like claw hand in ulnar nerve injury. Subsequent muscle wasting and atrophy will occur in longstanding cases.
● Loss of motor reflexes distal to the site of injury.
2- Sensory defects:
● Loss of sensation in the area supplied of the nerve. However the anesthetic area is usually smaller than that of the anatomical distribution of the nerve due to overlap of the dermatomes.
● Referred pain to the cutaneous distribution of the nerve is common in partial nerve injury. Severe burning sensation may occur and is named causalgia.
3- Sympathetic defects:
● Sudomotor effect: loss of sweating in the denervated area (anhydrosis)
● Vasomotor effects: Redness and hotness of the denervated skin due to sympathetic vasomotor paralysis. After 3 weeks the area becomes blue and cold due to loss of the afferent limb of vasomotor reflex.
4- Longstanding cases: Trophic changes occur due to disuse, vasomotor and sensory loss.
● The skin becomes smooth, thin and inelastic with trohic ulcers in the fingers, toes, nails and heels.
● The subcutaneous tissue becomes atrophied.
● The paralyzed muscles become atrophied and the antagonist muscles and their tendons will be shortened with apparent deformities.
● The joint capsules will be contracted with subsequent joint deformities.
● The bones will be rarified

Question 5

Clinical features of Nerve injury

Answer 5

1- Motor defects: Paralysis of the muscle group supplied by the injured nerve results in a deformity (Claw hand; ulnar nerve injury). Later there is muscle wasting and atrophy in longstanding cases. Also there is loss of motor reflex distal to the site of injury.

2- Sensory defects: Loss of sensation in the area supplied of the nerve. Referred pain to the cutaneous distribution of the nerve is common in partial nerve injury. Severe burning sensation may occur and is named causalgia.

3- Sympathetic defects:
● Sudomotor effect: loss of sweating in the denervated area (anhydrosis)
● Vasomotor effects: Redness and hotness of the denervated skin due to sympathetic vasomotor paralysis. After 3 weeks the area becomes blue and cold due to loss of the afferent limb of vasomotor reflex

4- Longstanding cases: Trophic changes occur due to disuse, vasomotor and sensory loss.
● The skin becomes smooth, thin and inelastic with trohic ulcers in the fingers, toes, nails and heels.
● The subcutaneous tissue becomes atrophied.
● The paralyzed muscles become atrophied and the antagonist muscles and their tendons will be shortened with apparent deformities.
● The joint capsules will be contracted with subsequent joint deformities.
● The bones will be rarified

Question 6

Clinical picture of Nerve injury

Answer 6

1- History of trauma in the course of the nerve either open or closed.
2- Type of the deformity
3- Motor defects in the muscle group supplied by the injured nerve
4- Sensory and sympathetic defects in the skin area supplied by the nerve.
5- Palpation of the nerve may reveal palpable neuroma.
6- Tinnel‘s sign: Tapping along the course of the nerve will elicit tingling sensation at the end of the regenerating nerve fibers. This is a good sign for follow up of the progress of nerve regeneration.

Question 7

Investigations used in nerve injury

Answer 7

1- Nerve conduction velocity (NCV)
2- Electromyography (EMG)
3- Recently ultrasonography and MRI are used for detection of anatomical interruption of the nerves.

Question 8

Conservative treatment of nerve injury indications and how its done?

Answer 8

Indications: Closed injuries with the hope to be of neuropraxia or axonotmesis type.
How?
1- Splinting to prevent muscle shortenin
2- Electrotherapy by galvanic current stimulation of the denervated muscle to prevent its atrophy till complete reinnervation.
3- Physiotherapy: passive and active exercises to prevent joint stiffness and edema.
4- The anaesthized part should be protected from injury and heat.

Question 9

Surgical repair of the nerve indications and how its done?

Answer 9

Aim: Restoration of the continuity of the nerve to give a chance for nerve regeneration.
Indications:
1- Open injuries
2- Closed nerve injuries with no manifestation of regeneration within 2 months after trauma.
3- Palpable neuroma.
How?
a- Primary nerve repair in early cases by microsurgical coaptation of the transected clean healthy ends of the nerve using microsutures by epineural repair. This is the ideal treatment.
b- Secondary nerve repair in late cases. Usually there is nerve shortening. After resection of the end neuroma till healthy nerve ends are seen, the gap between both ends is bridged by cable nerve grafts. This is usually done by harvesting the sural nerve in the leg and dividing it into segments named cables to bridge the defect by microsurgical techniques (Fig.4). A vascularized bed is essential for take of the graft. The results are inferior to the primary nerve repair

Question 10

Results of repair of nerve injury depend on ?

Answer 10

1- The injured nerve: Pure motor or sensory nerves are better than mixed nerves.
2- Level of injury: The higher the injury the worse the prognosis.
3- Timing of repair: The earlier the repair, the better the results. After 2 years there is almost no hope of recovery.
4- Gap between the cut ends: The longer the gap the worse the results.
5- Age and general condition of the patients: The results are more satisfactory in children and adolescents than older age groups. The patients with bad general
condition have lesser chance of recover than healthy individual

Question 11

What are the secondary procedures used in nerve injury?

Answer 11

Indications:
1- Longstanding cases
2- Failed or incomplete recovery after nerve repair.
Aim: Improve the function and correct the deformity
How?:
1- Muscle and tendon transfer either from nearby muscle groups or a muscle from another area in the body by microsurgical techniques.
2- Arthrodesis: Fixation of the joint in the functioning position.
3- Osteotomy: Correction of bone deformities.

Question 12

Mechanism of injury in brachial plexus

Answer 12

1- Open injuries: Gun shots or stab wounds in the lower part of posterior triangle of the neck.
2- Closed injuries:
Traction injuries either by forcible hyperabduction or depression of the shoulder
- Adult type
- Obstetrical type in difficult deliveries either breech or vertex presentation.
- Pressure injuries: Fractures and dislocation around the shoulder.

Question 13

Types of brachial injuries (clinical picture)

Answer 13

Obstetrical type:
● Total palsy affecting all roots.
● Upper palsy (Erb-Duchenne paralysis) affecting C5 - 6 ± C7.

Traumatic type:
● Total
● Upper palsy
● Lower palsy (Klumpke‘s paralysis): Only C8 and T1 are affected.

Question 14

Clinical picture of total type in brachial injury

Answer 14

● Flail arm: Complete paralysis of all muscles of the upper limb. The limb lies flaccid beside the patient

● Horner‘s syndrome may be present in avulsion injuries of T1 due to sympathetic paralysis of the face and eye (ptosis, myosis, anhydrosis and enophthalmos) of the affected side. It carries bad prognosis.

Question 15

Clinical picture of upper palsy

Answer 15

● C5-6: The flexors and extensors of the wrist and fingers as well as the small muscles of the hand are spared.
● C5,6,7: as above but with loss of wrist and finger extension (Wrist drop)
● The limb hangs beside the patient.
● The forearm is extended and pronated (policeman tip position).
● The shoulder cannot be abducted.
● The upper arm is internally rotated

Question 16

Clinical picture of lower palsy

Answer 16

● Normal movement of shoulder and upper arm.
● Paralysis of flexors of the wrist and fingers (C8).
● Paralysis of small muscles of the hand (claw hand deformity) (T1).
● Horner‘s syndrome may be present.

Question 17

ttt of brachial injury

Answer 17

Conservative
1- Physiotherapy to prevent muscle shortening and joint stiffness.
2- Electrotherapy of the affected muscles to prevent muscle wasting.
❖ It is indicated in closed injuries. Neuropraxia recovers in 2-3 weeks. Axonotmesis takes longer time.
❖ Rupture or avulsion injuries will never recover spontaneously.

Surgical treatment:
1- Nerve repair:
- It is indicated in open injuries and closed injuries that show no manifestations of recovery in 2 months duration.
- Exploration of the brachial plexus is done.
- The ruptured trunks are repaired by cable grafting.
- Avulsed roots cannot be repaired, so, their trunks can be repaired by cable grafting from intact roots or from other nerves outside the brachial plexus like spinal accessory nerve.
- Long period of rehabilitation program is needed for years.
2- Secondary procedures:
- Muscle transfer like latissimus dorsi muscle transfer to improve shoulder
abduction and external rotation.
- Osteotomies like osteotomy of the radius to improve the appearance of the
pronated deformity of the forearm.

Question 18

Clinical picture of radial nerve injury

Answer 18

1- Motor: The following muscles are paralyzed
* Triceps and anconeus muscles: Failure of elbow extension against gravity.
* Both muscles are escaped in injuries in the spiral groove.
* Extensors of the wrist and fingers: wrist drop and finger drop
* Supinator and brachioradialis: the forearm is pronated but supination can be done by biceps muscle.
2- Sensory: Anesthesia is variable and of no clinical importance.

Question 19

ttt of radial nerve injury

Answer 19

Conservative treatment:
In closed injuries for a period not more than 2 months.
1- Cock up splint to put the wrist and fingers in slight hyperextension to
prevent their stretch (Fig. 10)
2- Electrical stimulation of the affected muscle to prevent their wasting.

Surgical treatment:
Indications:
Open injuries
Closed injuries with no improvement after conservative treatment
1- Nerve repair: It gives good results when performed early and improvement is expected to be within a period of 9-12 months.
2- Secondary procedures: Tendon transfer from the flexors of the forearm to improve wrist and finger extension

Question 20

Clinical picture of median nerve injury

Answer 20

Motor
1)At or above the elbow:
* Paralysis of the flexor carpiradialis (FCR) resulting in weak wrist flexion and ulnar deviation of the hand on flexion.
* Paralysis of the flexor policis longus (FPL) resulting in failure of flexion of the distal interphalangeal joint of the thumb.
* Paralysis of the flexor digitorum superficialis (FDS)of all fingers and profunds(FDP) of the index finger resulting in loss of index flexion at all joints (pointing index)
* Paralysis of the small muscles of the hand supplied by the median nerve (Flexor policis brevis, abductor policis brevis, opponens policis and radial 2 lumbricals).
* The patient can not do palmar abduction of the thumb (ape like hand)
* Failure of opposition
* Wasting of the thenar eminence.

2)At the wrist:
* The long flexors of the wrist and fingers are spared.
* Only the small muscles supplied by the median nerve are paralyzed
* If the flexor tendons are also injured at that level the picture becomes more severe.

Sensory
* Loss of sensation in the palmar aspect of the radial side of the hand and the radial 3 and half fingers as well as the dorsal aspect of the distal phalangesof those fingers.
* Trophic changes in the tips of the above mentioned fingers

Question 21

Clinical features of Ulnar nerve injuries

Answer 21

Motor:
Above the elbow:
* Paralysis of the flexor carpi ulnaris (FCU) resulting in weak wrist flexion and radial deviation of the hand.
* Paralysis of the ulnar half of the FDP resulting in weak hand grasp especially of ring and little fingers.
* Paralysis of the following small muscles of the hand
1. Ulnar 2 lumbriclas resulting in partial clawing of the hand.
2. Interossessi resulting in failure of abduction and adduction of the ring, little and index fingers. The patient is unable to hold a sheet of paper between extended fingers (cardboard test)
3. Adductor policis muscle. When a sheet of paper is put between thumb and index finger, the patent will flex the distal phalanx. This is named Froment‘s sign
4. Flattening of the hypothenar eminence due to atrophy of hypothenar muscles
5. Hollowing of the interosseus spaces due to atrophy of dorsal inerossei

Sensory: Loss of sensation at the ulnar side of the forearm as well as the medial one and half fingers from the palmar and dorsal aspects.

At the level of the wrist:
Like above except:
✔ The FDP muscle is spared.
✔ The sensation of the forearm is normal.

Question 22

Clinical picture of Sciatic nerve injury

Answer 22

Motor:
Paralysis of all muscles below the knee and foot drop.
High injuries at the exit from the pelvis result in paralysis of hamstrings.

Sensory:
* Loss of sensation of leg and foot.
* Trophic changes of the sole of the foot.
* Causalgia in partial injuries of the nerve.

Question 23

ttt of sciatic nerve injury

Answer 23

Conservative treatment: General rules mentioned before Nerve repair.
Orthopedic operations: If the recovery does not follow repair in neglected cases secondary orthopedic procedures like:
1-Arthrodesis of the ankle
2-Below knee amputation in persistent severe causalgia or sever trophic changes.

Question 24

Clinical features of peroneal nerve injury

Answer 24

Motor:
* Paralysis of the extensor and peroneal groups of muscles of the leg resulting in dropped foot.
* In longstanding cases, the flexor group of muscle is shortened and contract resulting in paralytic equinovarus.