Carpal Tunnel Syndrome (CTS)
Carpal tunnel syndrome (CTS) is an entrapment neuropathy of the median nerve in the carpal tunnel at the wrist.
Causes and Risk Factors
- Activities with high hand / wrist repetition rate (wrist flexion or hand elevation)
- Gardening
- Assembly line work
- Use of vibrating hand tools
- Computer work (lack of consistent evidence)
- Obesity
- Pregnancy
- Osteoarthritis of the MCP joint
- Ganglion cyst
Secondary causes (more likely to cause bilateral carpal tunnel syndrome):
- Inflammatory joint disease (e.g. rheumatoid arthritis)
- Hypothyroidism
- Diabetes mellitus
- Amyloidosis
Clinical Features
Symptoms
Sensory symptoms are common:
- Burning pain / numbness / paraesthesia in the median nerve distribution
- Specifically, 1st to 3.5 digit of the palmar aspect (thumb, index, middle and radial half of ring finger)
- Palm sensation is intact (as the palmar cutaneous branch of the median nerve does not pass through the carpal tunnel)
- Symptoms are often worse at night
- Relieving factor: changing hand posture or shaking the wrist (flick sign) or hanging the arm / hand out of bed at night
Motor features are uncommon in early stages, usually only seen in advanced disease.
CTS is typically worse at night, classic history: “I wake up at night with numbness and have to shake my hand or hang it over the side of the bed.”
This is because there is ↑ tissue fluid / oedema at night, and people tend to sleep with their wrist flexed → ↑ carpal tunnel pressure.
Examination Findings
The following signs are associated with advanced disease:
- Motor deficit of the thenar muscles (LOAF: lateral 2 lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)
- Weak thumb opposition (most important) and thumb abduction
- Typically results in difficulty with pinch grip, buttoning, and holding small objects
- Late: thenar wasting
- Sensory loss in the median nerve distribution
- Specifically, 1st to 3.5 digit of the palmar aspect (thumb, index, middle and radial half of ring finger)
- Palm sensation is intact (as the palmar cutaneous branch of the median nerve does not pass through the carpal tunnel)
- Trophic ulceration at the tips of the digits (rare – indicates loss of protective sensation)
Certain hand provocation manoeuvres can be used to support the diagnosis of carpal tunnel syndrome:
- Phalen’s test: +ve if flexing the wrist for 60 seconds reproduces symptoms
- Tinel’s test:+ve if tapping lightly over the median nerve at the volar surface of the wrist reproduces symptoms
- Durkan’s test (carpal tunnel compression test): +ve if direct pressure over the proximal wrist crease reproduces symptoms
Carpal tunnel syndrome is a cause of low median nerve lesion, which presents differently from a high median nerve lesion. See the comparison table below:
| Feature | High median nerve lesion (above elbow) | Low median nerve lesion (wrist) |
|---|---|---|
| Common causes | Supracondylar fracture, elbow injury | Carpal tunnel syndrome |
| Forearm flexors (FDS, FDP II–III, FPL) | ❌Affected | ✅Unaffected |
| Thenar muscles (LOAF) | ❌Affected | ❌Affected |
| Finger flexion | ❌Affected | ✅Unaffected |
| Thumb opposition | ❌Affected | ❌Affected |
| Hand of benediction* | ✅Present | ❌NOT present |
| Thenar wasting | Possible | Common (late sign) |
| Sensory loss | Lateral palm + digits 1–3.5 | Digits 1–3.5, palm spared |
*The hand of benediction results from the inability to flex the index and middle fingers (innervated by the median nerve), but the patient is still able to flex the 4th and 5th digit (innervated by the ulnar nerve). This gives a deformity of the ring and little finger flexing normally, but the index and middle fingers remain extended (resembling a priest’s blessing gesture).
It is important to note that the hand looks relatively normal at rest, the hand of benediction deformity ONLY appears when the patient attempts to make a fist.
Investigation and Diagnosis
Carpal tunnel syndrome is primarily a clinical diagnosis if there are typical clinical features.
Further investigations can be performed in secondary care:
- Nerve conduction studies – if there is diagnostic uncertainty
- Blood tests – if secondary causes are suspected (e.g. rheumatoid arthritis, hypothyroidism)
Management
Carpal tunnel syndrome can be initially managed in primary care, only refer to secondary care if there is:
- Persistent symptoms despite primary care management, or
- Severe disease impacting daily function, or
- Diagnostic uncertainty
Primary Care Management
Advise on lifestyle changes (if possible):
- Avoid repetitive hand / wrist movements
- If possible, change in occupation or role
- If not possible, take regular breaks from tasks that precipitate symptoms
Optimise management of any underlying conditions
Offer a 6-week trial of conservative treatment; options include:
- Hand exercise and median nerve mobilisation techniques
- Wrist splint to be used at night (to maintain neutral wrist position)
- Corticosteroid injection (if appropriate expertise and experience available) – sometimes only performed in secondary care
- Generally not offered as 1st line
- Offers rapid symptom relief (up to 6 months), but effects are often temporary (limited long-term efficacy and recurrence is common)
Secondary Care Management
Carpal tunnel decompression (open / endoscopic technique)
- Recurrence rate post-surgery is 0.3-12 %
- Risks of surgery
- Scar
- Neurovascular damage
- Complex regional pain syndrome
In most patients, carpal tunnel decompression should only be offered if conservative treatment and corticosteroid injections fail.
However, immediate carpal tunnel decompression (without a trial of conservative care) is indicated in severe disease to prevent permanent median nerve damage, as suggested by: [Ref]
- Severe disease on electromyography
- Marked thenar muscle atrophy
- Objective weakness and constant numbness