DIAGNOSIS OF CARPAL TUNNEL SYNDROME: Ultrasound Versus Electromyography

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Carpal tunnel syndrome (CTS) was first described in the mid-1800s by Sir James Paget.15 It is defined as a spectrum of disease involving the hand and the wrist originating from problems related to the median nerve.1 It is probably the most well known of the peripheral compressive neuropathies, as well as being the fastest growing occupational disease in the United States. In fact, at least 1 person in 10 either develops this disorder or suffers symptoms from it in his or her lifetime.5 It is one of the most common causes of occupational absenteeism and disability, costing millions of dollars in lost productivity, not to mention the loss of hand function for the affected individual.4

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EPIDEMIOLOGY AND ETIOLOGY

CTS is associated with a welter of illnesses and conditions:

  • Occupations

  • Typists

  • Transcriptionists

  • Musicians

  • Jackhammer operators

  • Factory workers

  • Carpenters

  • Needle workers

  • Conditions

  • Pregnancy

  • Rheumatoid arthritis

  • Chronic renal failure

  • Diabetes mellitus

  • Wrist trauma

  • Amyloidosis

  • Tumors

  • Ganglia

  • Tendinitis or tenosynovitis

It most commonly affects people involved in tasks that require repeated motions and stresses of the hand and wrist. Although chronic illnesses, such as rheumatoid arthritis and chronic renal

DIAGNOSIS

Clinical diagnosis of CTS involves physical examination and electromyography (EMG). Typically, a patient presents with a history of numbness or weakness in the median nerve distribution. The symptoms can vary from mild pain due to repetitive activity to night pain and severe weakness. On physical examination, positive Tinel's and Phalen's signs are often elicited.16, 19 Thenar muscle atrophy is usually a late finding, consistent with chronic CTS. Conservative treatments including vitamin B6,

MEDIAN NERVE

The median nerve is a long peripheral nerve that originates from the brachial plexus to enervate the distal muscles of the hand as well as other structures along its course. It traverses the carpal tunnel, which is located in the volar aspect of the wrist just distal to the wrist crease. The median nerve is a small structure, but because of its superficial location, it is ideally imaged using high-frequency linear-array transducers.

Although ultrasound imaging of the median nerve has been

THREE-PHASE DESIGN

This investigation was designed in three phases in order to clarify the carpal tunnel anatomy, elucidate the ultrasound characteristics of the median nerve and the carpal tunnel, develop an understanding of the ultrasound changes with pathology, and finally evaluate the potential of ultrasound as a diagnostic tool for CTS.

Phase 1 was devoted to understanding the normal median nerve anatomy and determining its ultrasound characteristics. This was accomplished by cadaver dissection of the wrist,

CONCLUSION

Ultrasound is a simple technique to evaluate the median nerve and the contents of the carpal tunnel. The anatomy of the median nerve can be clearly defined and accurate measurements of its dimensions can be obtained. The abnormalities of the nerve, including edema, contour deformities, and enlargement of its cross-sectional area, can also be determined by ultrasound. There is a high degree of correlation between the conduction abnormalities of the median nerve as detected by EMG and the

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Address reprint requests to Doohi Lee, MD, Department of Radiology, Saint Mary's Hospital, 5801 Bremo Road, Richmond, VA 23226

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