Best Tests for Carpal Tunnel Syndrome
My colleague and fellow MedBridge instructor Eric Hegedus – who has published an infinite number of papers on diagnostic accuracy – recently created a theorem. Hegedus’s theorem states: “The total number of clinical tests that are available for a particular pathoanatomical diagnosis is inversely proportional to the likelihood that we will ever accurately diagnose the pathology of interest.” In other words, the more difficult the diagnoses are in the body region, the more special tests are available (e.g., sacroiliac joint, shoulder labrum). Carpal tunnel syndrome (CTS) is among the conditions that have many special tests but are challenging to diagnose.
Pathophysiology and symptoms
Carpal tunnel syndrome is the most common form of compression neuropathy in the upper extremities. It occurs when the median nerve is entrapped within the carpal tunnel of the wrist.
Symptoms vary but may include early involvement of the sensory systems and later involvement of the motor system. Within the hand, CTS generally affects the thumb, index, and middle finger and the radial half of the ring finger. However, atypical distributions are present and can make CTS diagnosis challenging.
The condition is relatively common among pathological processes. Prevalence rates range from 3% to 6% of individuals annually in the United States, affecting most often people of select occupations. CTS is more common in middle aged women and may have a presentation that is worst at night during sleep or in the daytime during activity.
Diagnosis and special tests
Carpal tunnel syndrome is generally considered a clinical diagnosis. This means that the signs and symptoms are the necessary criteria to consider the condition, whereas electro-diagnostic testing aids in confirming the diagnosis. Further, the condition is divided by acute and chronic CTS, with chronic CTS the most prevalent form seen by treating clinicians. Symptoms may involve burning, pain, numbness, and tingling, and less commonly clumsiness and weakness of the hand. Clinicians must rule out competing conditions such as cervical myelopathy or other forms of mononeuropathy.
Certainly, the clinicians that frequently treat CTS are going to be the best at identifying the condition. Clinicians who rarely care for patients with CTS may have to rely on a good physical examination and proper special tests and measures. Although, there is a wealth of special tests for CTS, only a few provide diagnostic utility consistently across a number of studies.
The two tests that have demonstrated the best diagnostic utility are the carpal compression test (in its many forms) and Phalen’s test (which is frequently incorrectly performed). The carpal compression test involves applied compression to the carpal tunnel region for a dedicated time, with the wrist in a flexed, extended, or neutral position. The amount of time past 1 minute of compression doesn’t seem to influence the accuracy of the test, nor does the wrist positioning. Phalen’s test is a static, passive test that involves allowing the wrist to hang in flexion for 2 or more minutes. See a demonstration of the compression test and Phalen’s test below.
Treatment
Treatment of CTS involves both conservative and surgical approaches. Unfortunately, surgical approaches are performed too frequently and should only be considered when symptoms are severe. Surgical approaches involve an open release and an endoscopic release, neither of which provide superior outcomes over the other. According to Ghasemi-rad and colleagues, conservative treatments may include splinting, cortical steroid injections, non-steroidal anti-inflammatory drugs, B6 vitamin, diuretics, ultrasound therapy, ergonomic positioning, manual therapy intervention, lidocaine patches, and acupuncture.
