Carpal tunnel syndrome

Risk factors

• Female
• Genetics?
• Diabetes
• OA/RA
• Obesity
• Hypothyroidism
• Pregnancy
• Trauma
• Aromatase inhibitors
• Environmental factors - controversial, may be associated with repetitive hand/wrist use, vibrating tools, sustained pressure
  • Probably NOT computer use

Pathophysiology:

• Caused by median nerve compression in the carpal tunnel, which can happen due to arthritic changes of the wrist joint, synovial sheath thickening or oedema
• Impaired sensation over 3.5 digits on the thumb side of the hand, and later in the disease course, wasting of the thenar muscles. No sensory loss over thenar eminence itself, since this area is supplied by the palmar branch of the median nerve (which enters the palm superficial to the flexor retinaculum).
• In median nerve damage at a higher level:
  • Thenar eminence won't be spared
  • Weakness of the relevant flexor muscles in the forearm (e.g. flexor pollicis longus) is a notable feature - check whether terminal phalanx of thumb can be flexed with normal power - in higher lesions this is lost.
• Can be repaired open, endoscopically or with USS as an essentially percutaneous procedure

Investigation

• Nerve conduction studies
  • High sensitivity and specificity and useful for gauging severity of median nerve injury
  • Demonstrate impaired median nerve conduction across the carpal tunnel with normal conduction elsewhere
  • Measure conduction velocity and amplitude of sensory and motor responses
  • Will see delayed latency with injury
• Electromyography (EMG)
  • Assesses for pathologic muscle changes
  • Excludes other conditions such as radiculopathy
  • Only necessary if there is diagnostic doubt
• USS
• MRI
  • Specificity and sensitivity 85-100% when using cross-sectional area >155mm/squared as cutoff

Differential diagnosis

• Cervical radiculopathy
  • Neck pain radiating into shoulder/arm
  • Exacerbation of symptoms with neck movement
  • Reduced reflexes
  • Weakness of proximal arm muscles
  • Sensory loss in forearm or medial palm
• Median neuropathy in forearm
• Cervical spondylotic myelopathy
• Brachial plexopathy
• Ischaemic stroke
  • Sudden onset
  • No pain
  • No single nerve distribution
• Motor neuron disease
  • Absence of pain
• Forearm or hand compartment syndrome
• Fibromyalgia
• Arthritis
  • Bilateral involvement
  • Involvement of joints other than wrist
  • Joint swelling
• Raynaud phenomenon
  • Provoked by cold/stress
• Pain from a ligamentous disruption

Symptoms

Clinical symptom grading

Mild symptoms

Tingling or discomfort in median nerve distribution, and

No sensory loss or weakness, and

CTS symptoms do not disrupt sleep, and

No difficulty with hand function or ADLs

Moderate symptoms

Sensory loss in median distribution, or

CTS symptoms (sensory loss or pain) interfere slightly with hand function but patient is able to perform all ADLs, or

Nocturnal symptoms may occasionally but not routinely disrupt sleep

Severe symptoms

Weakness in the median distribution, or

CTS symptoms disrupt one or more ADLs; patient is unable to carry out all previous activities, or

Nocturnal symptoms routinely disrupt sleep

EDX classification[1]

Mild CTS

Prolonged (relative or absolute) sensory latencies, and

Normal motor studies, and

No evidence for axon loss

Moderate CTS

Abnormal median sensory latencies as noted for mild CTS, and

Relative or absolute prolongation of median motor distal latency, and

No evidence of axon loss

Severe CTS

Any of the aforementioned NCS abnormalities with evidence of axon loss as defined by any of the following:

An absent or low-amplitude SNAP or mixed NAP

A low-amplitude or absent thenar CMAP

A needle EMG with fibrillation potentials or motor unit potential changes (large amplitude, long-duration motor unit potentials, or excessive polyphasics)

Diagnosis

• Phalen's test - bring dorsal hands together with elbows flexed. A positive test is pain or tingling on median nerve distribution within a minute.
• Tinel's sign - tap firmly over median nerve just proximal to carpal tunnel. Positive if symptoms are reproduced.
• Both have specificity of about 75%.

Treatment

Conservative treatment

• Wrist splint at night (prevent flex/ext)
• Corticosteroid injections

Indications for surgery: (always have electrodiagnostic proof prior to operating)

• Mild CTS unresponsive to conservative measures
• Moderate-to-severe CTS associated with axonal loss or denervation on electrodiagnostic studies
• If electrodiagnostic studies are normal, physical signs of median nerve dysfunction must be present in addition to classic symptoms

Technique

• Tourniquet
• LA
• Incision between distal wrist crease and Kaplan's cardinal line (from the apex of first interdigital fold towards ulnar aspect of hand, in line with middle crease of the hand), longitudinally aligned with radial edge of ring finger
• Fat
• Palmar fascia (see some muscle fibres - palmaris brevis)
• Transverse fascia ('transverse carpal ligament') - make a small hole, then get the nerve protector in and divide the rest of the ligament longitudinally over nerve, along the ulnar border of the transverse carpal ligament (stay away from thenar branch of median nerve). Check for full division proximally and distally with finger and metal instrument.
• 4/0 Vicryl rapide or nylon to skin (horizontal mattress)
• Opsite, crepe
• Release tourniquet

Tips

• Careful of motor branch of median nerve - don't stray towards thenar eminence
• And palmar cutaneous branch of median nerve is located more radially at wrist

Post-op

• Soft dressing for three days, then remove
• Elevate post-op
• Encourage active movements of fingers/wrist

Complications

• Inadequate division of transverse carpal ligament
• Injuries to recurrent motor or palmar cutaneous branches of median nerve
• Vascular injury to superficial palmar arch
• Infection
• Painful scar
• Complex regional pain syndrome