Carpal Tunnel Syndrome: Pathogenesis and clinical findings
Diabetes Mellitus (See Pathogenesis Slide)
↑ Blood sugar: deposition of advanced glycation end (AGE) products (proteins or lipids glycated when exposed to sugar)
AGE attaches to and prevents tendons from moving properly
Authors: Amanda Eslinger Yvette Ysabel Yao Reviewers: Matthew Harding Owen Stechishin Mao Ding, Cory Toth* * MD at time of publication
Wrist trauma (distal radius fractures, carpal/metacarpal fractures, tendon ruptures)
Repetitive Strain Injury (repetitive hand & wrist movements)
Irritation, swelling & thickening of tendons in carpal tunnel
Calcium deposits
Calcifica tion
Deposition Amyloidosis
Amyloid
(protein aggregates) deposition
Gout
(See Gout Slide)
Uric acid crystal deposition
Pregnancy
↑ Concentration of hormones & uterine pressure on inferior vena cava
Backup of blood into systemic circulation
Autoimmune
(i.e. Rheumatoid arthritis, scleroderma, lupus, Sjogren’s syndrome)
↑ Inflammatory cytokines causing inflammation
Hypo- thyroidism
Myxedema (swelling of skin and underlying tissues) in carpal tunnel
Idiopathic or Congenital
Edema
Narrowed carpal tunnel leads to ↑ internal pressure
Carpal Tunnel Syndrome
Vascular: median artery thrombosis in carpal tunnel
Median nerve compression inside the carpal tunnel Mechanical disruption of median nerve
Compression exacerbated with flexed wrists (i.e. sleep, driving, holding phone/cup)
Disruption of daily activities and sleep
Ischemia (↓ blood supply) to median nerve
Hypoxia (↓ oxygenated blood flow)
Metabolic conduction block (impaired axonal transport due to ischemia)
Nerve conduction study
(show sensory nerve impulses slowing across the wrist, followed by mild / moderate / severe loss of sensory nerve amplitude
Damage to the myelin sheath
↓ Saltatory conduction (action potential propagation along myelinated axons)
Neuropraxia (nerve compression blocks conduction)
Interruption in axonal continuity
Axonotmesis (endoneural tube stays intact but myelin & distal axon degenerates)
Recovery possible
Full disruption of myelin, axon & nerve sheath
Neurotmesis (axons no longer have an endoneural tube to guide regrowth)
Recovery impossible
↓ Ability to contract and use abductor pollicis brevis muscle
↓ Signals through median nerve
Interference with signals to the brain causes unusual sensations
Hypoalgesia (↓ pain Dysesthesia (tingling, burning, or sensitivity at 1st 3 1⁄2 digits) painful sensation at 1st 3 1⁄2 digits)
Thenar muscle wasting
Reduced hand dexterity
Weak thumb abduction
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published December 2nd, 2013, updated March 22, 2023 on www.thecalgaryguide.com