Clinical Question
How is carpal tunnel syndrome (CTS) diagnosed clinically and how can the history and physical examination inform evidence-based management?
Evidence Summary
CTS is the most common entrapment neuropathy seen in primary care. It is caused by compression of the median nerve in the space underneath the wrist flexor retinaculum, which can produce pain in the wrist or lateral digits and thumb, paresthesia, and, in severe cases, sensory loss and weakness or atrophy of thenar muscles.
History and physical examination elements, including provocative tests, have limited accuracy compared with electrodiagnostic testing for the diagnosis of CTS. The Phalen sign has a positive likelihood ratio (LR+) of 1.4 and a negative likelihood ratio (LR−) of 0.7, and the Tinel sign has an LR+ of 1.3 and LR− of 0.8.1,2 Hypalgesia in the median nerve distribution is minimally to moderately useful for ruling in CTS, with an LR+ of 3.1, and weak thumb abduction has an LR+ of 1.8.1 A systematic review concluded that the Katz hand sensory symptom diagrams may be useful.1 According to an evidence-based guideline from the American Academy of Orthopaedic Surgery, there is strong evidence that no test alone can diagnose CTS, but the presence of thenar atrophy is useful for ruling in CTS.3 The majority of studies that examined sensitivity and specificity of history and physical examination findings for CTS were performed in specialty settings, limiting the usefulness of these findings in primary care. However, one study found that 81% of patients referred by family physicians for clinically suspected CTS had the diagnosis confirmed by a neurologist.4
The CTS-6, a validated risk score, is useful for making the diagnosis and assessing severity of CTS.5 The CTS-6 assigns points for six signs and symptoms (Table 16,7 ). Although there is no consensus on a diagnostic reference standard for CTS, a 2014 study found that compared with electrodiagnostic testing, a CTS-6 score of 12 or more had a sensitivity of 89%, a specificity of 80%, an LR+ of 4.5, and an LR− of 0.14.6 A CTS-6 score of 18 or more is 99% specific for CTS, but is only 31% sensitive (LR+ = 31, LR− = 0.70).7
TABLE 1. CTS-6 Risk Score for Diagnosing Carpal Tunnel Syndrome
| Symptom or sign | Points |
|---|---|
| Thenar atrophy or weakness | 5.0 |
| Positive Phalen test | 5.0 |
| Loss of 2-point discrimination | 4.5 |
| Nocturnal numbness | 4.0 |
| Positive Tinel sign | 4.0 |
| Numbness predominantly or exclusively in median nerve distribution | 3.5 |
| Total (range 0 to 26) | _____ |
Note: For a cutoff of ≥ 12 points, the LR+ is 4.5 and the LR− is 0.14. If pretest probability is 50%, positive predictive value is 82% and negative predictive value is 12%. For a cutoff of ≥ 18 points, the LR+ is 31 and the LR− is 0.70. If pretest probability is 50%, positive predictive value is 97% and negative predictive value is 41%.
LR+ = positive likelihood ratio; LR− = negative likelihood ratio.
Symptom severity determines management. Severe CTS presents with thenar atrophy, median nerve sensory loss, and persistent nocturnal symptoms. Severe CTS can also develop in patients for whom conservative treatment has been unsuccessful. Patients who have CTS, especially with severe thenar atrophy, may benefit from early referral for surgical consideration and specialized diagnostic testing. A systematic review found better outcomes for severe CTS with surgery at 6 months, but not at 3 or 12 months.8 Activity limitations, splinting, and corticosteroid injections may be effective treatment options for patients with nonsevere CTS.9,10 A high score on the CTS-6 tool has a weak positive correlation with higher severity grades on electrodiagnostic testing.11
Patients may be considered for surgery if they have insufficient symptom relief after a trial of conservative management or severe symptoms and functional impairments.3 There are no widely accepted tools to determine which patients may have successful surgical outcomes. A multivariate prognostic model based on data from more than 3,000 patients found that moderately severe or worse nerve conduction abnormalities, female sex, family history, and symptoms that are relieved by shaking the hand were associated with better patient-reported surgical outcomes.12
Applying the Evidence
An otherwise healthy 42-year-old woman who works as a data entry clerk presents with numbness and tingling in the first, second, and third digits of her dominant hand with pain radiating up her arm. Her symptoms occur at night and are relieved by shaking her hand. She does not have thenar atrophy. Her Phalen and Tinel tests are both positive. She has normal 2-point discrimination. You determine she has mild to moderate CTS based on a CTS-6 score of 16.5 and recommend workplace duty alterations and a wrist splint. You suggest follow-up in 2 months to assess her symptoms and to consider a corticosteroid injection. You advise her that surgery may be an option if she has persistent symptoms after 6 months of conservative management or worsening symptoms with functional impairments. Nerve conduction studies may help determine if surgery is likely to be beneficial.
Editor's Note: Dr. Brown is a contributing editor for AFP.
