Carpal Tunnel Syndrome in Emergency Medicine Workup

Updated: Sep 08, 2016
  • Author: Jeffrey G Norvell, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Workup

Imaging Studies

Currently, there is no universally accepted criterion standard for the diagnosis of carpal tunnel syndrome (CTS). The diagnosis of CTS is made from the ED presumptively. The clinician who follows the patient after the acute presentation usually orders the imaging studies and other tests discussed below.

Magnetic resonance imaging (MRI) is reasonably accurate in diagnosing CTS. Currently, this imaging modality is only recommended when the clinical picture is confusing or when nerve conduction studies are equivocal or contradictory. Dynamic MRI imaging may be useful in identifying dynamic CTS (CTS symptoms brought on only by repetitive wrist motion). [15] MRI may also identify causative lesions in carpal tunnel. [16]

See the images below.

Carpal tunnel syndrome. Axial fast spin-echo T2-we Carpal tunnel syndrome. Axial fast spin-echo T2-weighted MRI with fat saturation. Note the increased T2-weighted signal within the median nerve (arrow). A slightly increased cross sectional area of the nerve is noted but the nerve architecture is preserved, consistent with early or mild inflammation.
Carpal tunnel syndrome. Fast spin-echo T2-weighted Carpal tunnel syndrome. Fast spin-echo T2-weighted MRI illustrates more pronounced increased signal within the median nerve (arrow). Note the small amount of fluid within the carpal tunnel, a secondary sign of inflammation. Slightly less optimal fat saturation is noted than on other images, which is a common occurrence.
Carpal tunnel syndrome. Axial fast spin-echo T2-we Carpal tunnel syndrome. Axial fast spin-echo T2-weighted MRI with greater increase in signal and loss of definition within the nerve (arrow). Inflammatory change is noted within the carpal tunnel, adjacent to the flexor digitorum superficialis tendons. The appearance is consistent with pronounced inflammatory change within the carpal tunnel.

Plain radiography is low-yield. [17]

High-resolution ultrasonography (US) has received increased attention in the evaluation of CTS. US as a modality is more widely available than electrodiagnostic studies and is noninvasive and has lower costs. Recent US studies have shown that patients with CTS have an increased cross-sectional area of the median nerve in the carpal tunnel than controls. One study showed that both the cross-sectional area of the median nerve in the wrist (CSA-M) and of the ratio of the area of the median nerve between the wrist and the forearm (R-WF) were useful measures in the diagnosis of CTS, using electroneuromyography (ENG) as a reference test. [18]

Ultrasonography may be useful as an alternative to nerve conduction studies for an initial diagnostic test for CTS. [19, 6, 18, 20] One study concluded that sonography is not accurate enough to replace nerve conduction studies for diagnosing CTS. [21]

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Other Tests

Electromyographic (EMG) and nerve conduction studies

EMG and nerve conduction studies help confirm the diagnosis of CTS. They are most helpful in the determination of the site and severity of nerve compression.

Electrodiagnostic testing has been found to have an 85% sensitivity and a specificity greater than 95% for diagnosing CTS. [4]

Clinically symptomatic CTS may have normal nerve conduction findings. [22]

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