Carpal Tunnel Syndrome

The most common entrapment neuropathy you will see, and the one students over-test.

Illness script in one line: numbness, tingling or burning in the thumb, index, middle and radial half of the ring finger, worst at night, waking them, relieved by shaking or flicking the hand — with dropping things and a vague sense of weakness as it goes on.

Caseload frequency: common, and commoner still on a hand, occupational or women's health caseload. Read further: global and regional prevalence [1], general-population prevalence [2], lifetime prevalence, annual incidence and risk factors for carpal tunnel release [3].

The history makes this diagnosis. Your tests don't.

This is a 70/30 pattern in its purest form: night symptoms are the diagnostic giveaway.

Read further: diagnostic test accuracy of scales, questionnaires and hand symptom diagrams [4], clinical utility of the CTS-6, the Boston-CTS and the hand diagram [5], sensitivity and specificity of electrodiagnostic parameters [6].

The direction, which is all you need:

That is not a licence to skip the objective exam. It is a reason to spend your objective time on the two things that change management — motor loss and thenar bulk — rather than on three provocative tests you will do badly and interpret worse.

Main problem

"My hand goes numb at night." Or dead, or asleep, or on fire. Numbness, tingling or burning in the thumb, index, middle and radial half of the ring finger.

The complaint is sensory first and motor second. A patient whose opening line is weakness, with no sensory story, is a different page.

Body chart

Median distribution — thumb, index, middle, radial half of ring.

Two things students get wrong with it:

• Plenty of genuine carpal tunnel patients report the whole hand. They are not lying and it does not rule it out. Ask them to shade it, then ask specifically about the little finger. Little-finger symptoms don't exclude it either — carpal tunnel can refer outside the median territory — but a clearly ulnar pattern, a neck relationship or a dermatomal march should send you screening wider.
• The palm is often spared, because the palmar cutaneous branch of the median nerve leaves proximal to the tunnel. Numbness over the thenar eminence and central palm points you proximal, not distal.

Proximal ache into the forearm and even the shoulder is common and does not make it cervical.

Behaviour

Worse at night, with gripping, and with sustained wrist flexion. Relief by shaking or flicking the wrist.

Night waking is the single most useful item in the history and it is worth asking about properly: what time, how many times, what they do about it, whether they've started sleeping with the hand out of the bed. The pearl that night symptoms are the diagnostic giveaway is the line the evidence supports, and the structured symptom tools that carry the diagnostic accuracy work are built around exactly this kind of item.

The flick sign is a genuine discriminator. People with cervical radicular pain do not shake their hand at 3am and get relief in thirty seconds.

Aggs: night, sustained wrist flexion or extension, driving, holding a phone or book, gripping, vibration.
Eases: shaking, flicking, changing hand position, hanging the arm out of the bed.
Severity: VAS 0–10 at best / at worst / right now.

History

Gradual, fluctuating, months. Intermittent at first, then more nights, then daytime, then constant. Constant numbness is a change in stage, not just a worse day — see section 4.

Special / screening questions

Repetitive use, pregnancy, diabetes, hypothyroidism. All four earn their place.

• Pregnancy and postpartum. Different prognosis conversation — it commonly settles. Splint, reassure, review. The same patient is often being seen for De Quervain's at the same time. Read further: carpal tunnel syndrome in pregnancy [7].
• Occupation. Ask about vibration and forceful repetitive grip, not just typing. Read further: causes, mechanisms, diagnosis and management of occupational carpal tunnel syndrome [8].
• Diabetes and thyroid disease. Ask. It changes the referral letter.
• Bilateral, older, and no occupational explanation — go to section 4 before you go to section 6.

The discriminator that does most of the work: what does the little finger do, and does the neck change anything.