Peripheral nerve injuries

Structure of the nerve

Axon

myeline sheath

Schwann cell layer

Endoneurium

Perineurium

Epineurium

Pathology

The nerve is injured by:

Ischaemia

Compression

Traction

Laceration

burning

Types of injury

•Transient ischaemia

•Neurapraxia

•Axonotmesis

•Neurotmesis

Transient ischaemia

Acute nerve compression →

Acute endoneural anoxia →

Temporary numbness + muscle wasting

Recovery by 10 minutes

Neurapraxia

Chronic mechanical pressure →

Demyelination of axon

Spontaneous recovery after few days or weeks

Axonotmesis

• Segmental interruption of the axons

• Loss of conduction

• But the neural tubes are intact

• Seen in closed fractures and dislocations

• Distal to the lesion → Wallerian degeneration

• Axonal regeneration occurs by formation of the new axonal processes which grow at a speed of 1-2 mm per t

Neurotmesis

Division of the nerve trunk

Occurs in open wounds

Neural tubes are destroyed

A Neuroma is formed( regenerating fibers + Schwann cells + fibroblasts)

Function may be adequate but is never normal even after surgical repair.

Diagnosis

Symptoms: (1) Numbness (2) Tingling (3) Weakness

Signs: (1) Abnormal posture ( wrist drop) (2) Atrophy of the muscles (3) Change in sensibility

Tinels sign: shows progression in nerve recovery

Electrodiagnostic tests (1) level of injury (2) Severity (3) progress of nerve recovery

Obstetric brachial plexus injuries

Caused by excessive traction on the brachial plexus during childbirth.C5+C6+C7+C8+T1

Clinical features:•Difficult delivery•Flail arm.

•Further examination reveals one of the following: (A) Erb’s palsy (B) klumpke’s palsy

Erb’s palsy:

Injury of C5+ C6

The arm is held to the side, internally rotated, and pronated.

(i.e paralysis of the abductors and external rotators of the shoulder + the supinators)

Klumpke’s palsy:

Less common

The arm is flail and pale

All muscles of the fingers are paralyzed

± Ipsilateral Horner’s syndrome

Treatment:

If there is no biceps recovery by 3 months, surgery is performed:

If the roots are not avulsed: Nerve graft

If the roots are avulsed : Nerve transfer

If severe internal rotation : Subscapularis release ± tendon transfer OR Rotation osteotomy of the humerus

Physiotherapy in all cases

Prognosis in Klumpke’s palsy is poor.

Axillary nerve injury (C5)

Supplies (1) Deltoid (2) Skin over the lower ½ of the deltoid.

Injured in (1) Shoulder dislocation (2) # of humeral neck

Clinically (1) Loss of abduction (2) Numbness over the deltoid.

Treatment:

Spontaneous recovery during 8 weeks. If not:

Exploration + repair OR graft. If failed:

Tendon transfer OR Shoulder arthrodesis. .