Carpal Tunnel Syndrome might be diagnosed (in part) by the presence of a so-called Tinel’s Sign. What is that and why is it not a true sign?
Carpal tunnel syndrome might be diagnosed (in part) by objective information such as the results of nerve conduction testing, ultrasound measurements, and the presence of thenar muscle atrophy. Nonetheless, the diagnosis of carpal tunnel syndrome relies heavily on the report of classical symptoms such as numbness and tingling in the distribution of the median nerve, nocturnal wrist or hand pain, and decreased sensation.
Tinel's test can be employed to help diagnosis carpal tunnel syndrome as well. Tinel’s test is performed by tapping the volar surface of the wrist at the point where the median nerve passes through the carpal tunnel (Figure 1 and Figure 2)
Figure 1: the examiner is performing Tinel's test by tapping the wrist right over the medial nerve within the carpal tunnel.
Figure 2: Carpal Tunnel Anatomy: the median nerve accompanies the flexor tendons as they pass through the carpal tunnel at the wrist. (Wikipedia. http://bit.ly/1Q7JcxZ)
Tinel's test is considered positive when the patient reports a sensation of tingling in the median nerve distribution of the hand (Figure 3). This response is called a “Tinel’s sign.”
Figure 3: Dermatomal distribution of the median nerve shown in yellow. If the medial nerve is compressed at the wrist, sensory changes are expected to be reported only within this territory (Modified from Wikipedia.https://commons.wikimedia.org/wiki/Category:Dermatomes_of_the_human_hand#/media/File:Grant_1962_84.png)
A positive Tinel’s tests is not a sign, however, as it reflects a subjective sensation experienced and reported by the patient. By contrast, signs are objective findings that are noted by the observer, independent of the perceptions and report of the subject–and a description of a sensation is not that. (A body temperature of 39 degrees is an objective finding; the report “I am hot” is subjective. And needless to say, a patient with a body temperature of 39 degrees may indeed report “I feel chills.”)
The response to a Tinel's test might better be termed a "wign"*. This word is pronounced "whine" to remind us it is a spoken response, and its spelling echoes that of sign, reminding us likewise that a “wign” might be more specific than a general patient complaint. In the case of carpal tunnel syndrome, one manifestation of “specificity” might be that the complaints indeed respect the dermatomal borders shown in Figure 3. That is, a report of tingling in the 5th finger is
(Tinel’s is not the only wign in musculoskeletal medicine. A patient reporting pain with forward elevation of the shoulder (due, most likely, to rotator cuff tendinosis) might be described as demonstrating an impingement wign, not impingement sign (as it is frequently but mistakenly called)).
Additional Points to Consider
You might wonder why the distinction between objective and subjective is worthy of preservation. After all, if the job of the physician is to mitigate suffering, then the patient’s complaints should be paramount and they usually are. That is not to say, however, that complaints should always be the sole basis of diagnosis. If nothing else, the physician’s perception of patients’ description may not match the underlying original perception. Also, if we’ll be open about it, patients are not always completely forthcoming or honest about their symptoms. This is particularly germane with of carpal tunnel syndrome, whose status as a possible work-related condition is contentiously debated**.
* Fine Wigns Clin Orthop Relat Res. 2010 Apr; 468(4): 1165–1167. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2835601/
** Carpal Tunnel Syndrome is Work-related-Because I Said So. Clin Orthop Relat Res. 2020;478(6):1173‐1177. https://pubmed.ncbi.nlm.nih.gov/32282535/