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Introduction

Carpal tunnel syndrome is a relatively common disorder, which can be unilateral or bilateral, caused by compression of the median nerve at the level of the wrist, as it passes through the ‘carpal tunnel’.

Patients typically initially complain of parasthesia (“pins and needles”) in the distribution of the median nerve – the thumb, index, middle and half of the ring finger on the affected side. This may progress to pain in the same distribution as the condition progresses.

Symptoms are classically worse at night – often waking the patient from sleep, and patients will commonly report that ‘hanging the arm over the side of the bed’, or getting up and ‘shaking the arms’ relieves the symptoms.

  • Pain may also be felt in the wrist, forearm, and can even radiate as far as the shoulder

Symptoms are typically provoked by use of the hand and wrist, but occur after rather than during the activity. In advanced disease, there may be weakness of the grip, particularly the thumb, possibly including the classical “wasting of the thenar eminence” (the muscular mass at the base of the thumb).

Carpal Tunnel Syndrome Overview

Carpal Tunnel Syndrome Overview. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Epidemiology and Aetiology

  • Affects about 5% of the population
    • Estimates vary from 1-10%
  • More common in women
  • Typical presentation at age 30-50
  • Associated with:
  • Tasks that involve repetitive flexing and/or vibration of the wrist are likely to predispose to the condition
    • E.g. meat packers, production line workers
    • Sports – tennis, cycling, throwing
    • RSI – repetitive strain injury – is a a generic term that should be avoided. There is usually a more specific diagnosis, such as intersection syndrome, De Quervain tenosynovitis, or carpal tunnel syndrome
  • Most cases are ideopathic (no cause identified)

Pathology

  • Compression of the median nerve as it passes through the carpal tunnel (under the flexor retinaculum)
  • It is thought that a flexor tenosynovitis develops (as opposed to De Quervain tenosynovitis – which is an extensor tenosynovitis), and the swelling associated with this compresses the median nerve as it passes through the carpal tunnel.
Anatomy of carpal tunnel syndrome

Anatomy of carpal tunnel syndrome. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Signs and symptoms 

These are the signs of of median nerve compression:
  • Wasting of the thenar eminence (the chunky muscle on the palmar aspect of the base of the thumb) – is often a late sign
  • Parasthesia of the lateral 3½ fingers (thumb, forefinger and middle finger)
  • Pain / tingling in the lateral 3 fingers
    • Pain is often worse at night and may wake the patient. It is often a burning or aching sensation.
  • The median nerve also supplies the lateral part of the palm but typically, this is spared as this branch of the median nerve does not pass through the carpal tunnel.
Late carpal tunnel syndrome

Late carpal tunnel syndrome, showing bilateral wasting of the thenar eminence. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Examination

  • Look for wasting of the thenar eminence (late sign)
  • Check sensation on the lateral 3½ fingers
  • Check the power in the fingers
    • Reduced thumb or grip strength indicated the need for urgent specialist referral
  • The self-administered hand diagram
    • Is the most useful test – and is about 75% sensitive for carpal tunnel syndrome
      • As the patient to draw around their hand(s) on a piece of paper
      • Then ask them to shade the affected areas
      • A positive test is where the shaded areas correspond well to the median nerve distribution
Median Nerve Distribution

Median Nerve Distribution. Image from page 851 of “Internal medicine; a work for the practicing physician on diagnosis and treatment, with a complete Desk index” (1920)

  • Durkan’s Test – This is the most sensitive test for carpal tunnel syndrome
    • The examiner presses over the carpal tunnel with their thumbs for 30 seconds
    • Onset of pain or parasthesia in the distribution of the median nerve is a positive test
  • Phalen Test – ask the patient to hold their wrists in a flexed position for 60 seconds. May elicit / exaggerate typical symptoms
  • Tinel’s Test – tap over the medial aspect of the inside of the wrist. Can induce tingling sensations. Less likely to elicit signs than Phalens
    • “Tinels – Tapping, Phalen – Flexing”
    • Both Tinel’s and Phalen tests are not very specific for Carpal Tunnel syndrome

Investigations

  • Diagnosis is usually clinical, but occasionally in difficult cases, nerve conduction studies may be performed
    • History and examination is usually more useful
  • Consider investigation for any potentially undiagnosed underlying disorders – such as hypothyroidism or diabetes

Management

In addition to below, treat any underling disorder (e.g. hypothyroidism, diabetes, obesity).

1st line

  • Conservative
    • Modification of activities – e.g. keyboard position at work, identification and avoidance of flexing activities
    • Splint – can be worn at night to reduce nocturnal symptoms. Particularly useful for patients with night-time only symptoms
    • Pain relief – is typically in the form of NSAIDs
    • Consider specialist hand physiotherapy

2nd line

  • Carpal Injection – corticosteroids – e.g. hydrocortisone acetate – can be used if other methods have failed to control symptoms. Inject just dorsal to the wrist crease.
    • Effective in about 80% of cases
      • Failure to improve after injection is  poor prognostic indicator
      • Less likely to respond if symptoms >6 months duration, or if >3 previous injections
    • Typically wears off after a few months
    • 20% will be pain free at 1 year
    • May cause a sensation of shooting and tingling if you touch the nerve. If this is the case, you are in the wrong place! You are not aiming for the nerve itself, but for the flexor tendons.
    • Wearing a splint for a few days after injection can reduce the symptoms induced at time of treatment

3rd line

  • Surgical decompression can be used for patients who still fail to respond to the above, or whom have presented with advanced disease (reduced grip strength and/or wasting of the thenar eminence). This can be open or endoscopic surgery.
    • Patients who have had previous temporary improve after corticosteroid injection tend to have better surgical outcome
    • Open vs endoscopic techniques have similar symptom-relief outcomes, but open procedures tend to have fewer complications

Flashcard

References

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