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 (electrodiagnostic) testing, ultrasound measurements or the presence of thenar muscle atrophy. Nonetheless, the diagnosis of this syndrome relies heavily on the report of symptoms. A study by Graham in The Journal of Bone and Joint Surgery in 2008, for instance, reported that when numbness in the median nerve distribution, paresthesias produced by holding the wrists in a position of maximal flexion for 30 seconds (the so-called Phalen’s maneuver) and Tinel's sign are present, there is at least an 80% chance that the patient has carpal tunnel syndrome.
A Tinel’s sign (named after the French neurologist Jules Tinel) is elicited 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).
If the patient reports a sensation of tingling in the median nerve distribution of the hand (Figure 3), a “Tinel’s sign" is said to be present.
A positive Tinel’s tests is not a sign in the true sense of the word, however, as it reflects a subjective sensation experienced and reported by the patient--a symptom, in other words.
Additional Points to Consider
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 clearly not related to carpal tunnel syndrome (as the 5th finger is supplied by the ulnar, not median, nerve). As such, a report of tingling in the 5th finger, in response to tapping the over the median nerve, would clearly not count as a positive response.
(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)).
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/