Nerve Injuries in the Upper Limb

Nerve Injuries in the Upper Limb

• The presentation focuses on investigating nerve injuries in the upper limb within the musculoskeletal system.
• Topics include nerve anatomy and histology, types of nerve injuries, causes of nerve injuries, diagnosis of nerve injuries, and specific examples of upper limb nerve injuries.

Nerve Anatomy and Histology

• A nerve is composed of bundles of axons (nerve fibers) along with connective tissues: epineurium (outer layer), perineurium (wraps fascicles), and endoneurium (surrounds individual axons).
• Axons can be myelinated or unmyelinated. Myelinated axons have a myelin sheath, with Nodes of Ranvier.
• Blood vessels run alongside the nerve.

Nerve Injury Types

• Neuropraxia: Transient interruption in nerve conduction. Temporary loss of function that reverses within hours to months. Caused by compression, blunt blows or shock injuries. Motor function often affected more than sensory.

• Axonotmesis: Severe crush or contusion. Loss of axon continuity, but the epineurial and endoneurial tubules remain intact. Equal loss of motor and sensory components. Axon regrowth happens at a rate of 1-3 mm per day.

• Neurotmesis: Severe contusion, stretch or laceration. Complete loss of motor, sensory, and autonomic function. Continuity of the nerve's connective tissue is lost. Outcome is more favorable if only the endoneurial tube is damaged.

Causes of Nerve Injuries

• Mechanical: Compression, traction, laceration.
• Others: Metabolic, ischemia, thermal, radiation.

Diagnosis of Nerve Injuries

• History: Patient's account of the injury.
• Clinical examination: Assessment for weakness, wasting (muscle loss), flaccidity, loss of sensation (pain/temperature/fine touch), and loss of sweating.

Examples of Nerve Injuries in the Upper Limb

• Erb's Palsy: Nerve injury affecting shoulder, arm, and hand movement in infants. Often caused by shoulder dystocia, causing traction injury to the brachial plexus (C5-6). Involved nerves include suprascapular, musculocutaneous, and axillary. Characteristics include arm hanging by side, rotated medially, forearm extended and pronated. Biceps damage is called 'waiter's tip'. Treatments involve nerve transplants, subscapularis releases, and latissimus dorsi tendon transfers.

• Klumpke's Paralysis: Paralysis affecting forearm and hand muscles. Results from brachial plexus injury that affects the C8 and T1 nerves. Affects intrinsic muscles of the hand and wrist/finger flexors (flexor digitorum profundus ulnar half).

• Claw Hand: Occurs due to ulnar nerve laceration at the wrist joint. Loss of intrinsic hand muscles (interossei) leading to difficulties with abduction/adduction of fingers. Medial two lumbrical paralysis greatly reduces little and ring finger movement. Characterised by a hand deformity called "ulnar claw".

• Wrist Drop: A sign of radial nerve injury. Usually caused by humerus dislocations or fractures. Paralysis of triceps and posterior compartment muscles. Inability to extend the elbow, wrist, and fingers. Loss of sensation over the radial nerve's cutaneous innervation.

• Carpal Tunnel Syndrome: Median nerve entrapment which causes numbness, pain, or paresthesia (pins and needles) in the thumb, index, long, ring, or part of the little fingers. Risk factors include: diabetes, obesity, pregnancy, hypothyroidism, and heavy manual work involving vibrating tools. Conservative treatments include night splints and corticosteroid injections.

This quiz explores nerve injuries in the upper limb, focusing on anatomy, types of injuries, their causes, diagnosis, and examples. Learn about the histological structure of nerves and the implications of different injury types such as neuropraxia and axonotmesis.