The diagnosis of recurrent carpal tunnel syndrome begins with a thorough history, attempting to document symptoms prior to primary carpal tunnel decompression, including details such as nighttime awakening, daytime numbness, whether the numbness was intermittent or constant, and whether the initial symptoms were confined to the median nerve distribution [12, 13]. Pain should be differentiated from numbness, as many patients perceive all wrist or hand pain to be synonymous with carpal tunnel syndrome. In addition, any preoperative electrodiagnostic studies should be obtained. In summary, the anatomic distribution of symptoms, specific symptoms, and exacerbating and alleviating factors if any are all important aspects of the history that will help in diagnosing recurrence.

Following the establishment of the clinical picture prior to the initial diagnosis of carpal tunnel syndrome, one must elicit the patient’s description of events surrounding decompression and the return of symptoms. It is important to determine if any symptoms improved or resolved, if any symptoms worsened, and the timing of these. The goal is to determine whether the patient has persistent, recurrent, or new symptoms [11]. An improvement in position-specific symptoms, improvement in paresthesias , or improvement in intermittent pain all point toward a complete release of the transverse carpal ligament. If the same symptoms return after a symptom-free interval, true recurrence is likely. Persistent numbness may be due to chronic compression and does not always improve following complete release of the ligament. One may consider baseline Semmes-Weinstein testing to observe improvement over time [14]. If intermittent symptoms worsen or new symptoms develop immediately following surgery, one has to consider iatrogenic nerve injury. No change in intermittent symptoms may cause one to consider an incomplete release. Of note, at least one study in the literature has found hypertension and diabetes to be associated with recurrence of carpal tunnel syndrome [15]. Thus, one should still take a full history, including a complete past medical history, family, and social history. Amyloidosis and inflammatory disorders can also cause proliferative tenosynovitis and contribute to symptoms for which a patient is seeking revision carpal tunnel surgery [2].

Another important reason for a detailed history is to determine whether the initial diagnosis of carpal tunnel syndrome was correct. It is possible that a patient presenting with a wide variety of hand and wrist complaints is diagnosed with carpal tunnel syndrome. Conditions such as ulnar neuropathy, basal joint arthritis, or compression of the median nerve proximal to the carpal tunnel are all conditions that may coexist or be mistakenly diagnosed as carpal tunnel syndrome. In addition, the patient may have electrical studies that indicate median nerve compression at the carpal tunnel, but clinical symptoms that are not typical for CTS and do not respond to carpal tunnel release.

The physical examination should be thorough and include the entire upper extremity, evaluating for other common conditions that may coexist with CTS. In addition, other areas of nerve compression must be ruled out, including compression proximally such as with pronator syndrome and even cervical spine pathology. The exam begins with inspection and comparison to the contralateral limb, beginning at the hand and working proximally. Skin color and any warmth or erythema is noted. Thenar strength is evaluated, noting any atrophy that may be present. The prior incision is also inspected and then palpated. Tenderness anywhere along the incision site is noted as well as tapping on the nerve to illicit a Tinel sign.

The sensory exam is of particular importance. This consists of light touch and two-point discrimination. Decreased two-point discrimination can be a late finding in median nerve compression and may still be present following a complete carpal tunnel release. Similarly, a change in threshold with Semmes-Weinstein monofilament may be present in chronic nerve compression even after complete release. However, this information is useful in comparing the bilateral upper extremities as well as having a comparison to the exam prior to initial release if these data were obtained. When checking two-point discrimination, it is important to be oriented in a longitudinal direction to prevent measurement of the adjacent digital nerve [16].

Motor function of the intrinsic muscles is important in the physical examination for carpal tunnel syndrome. Opposition of the thumb to the little finger is used to test thenar muscle function and median nerve innervation. When testing opposition and strength, one should note that the deep head of the flexor pollicis brevis (innervated by the ulnar nerve) and the flexor pollicis longus can flex the thumb across the palm to the little finger [16].

Specific provocative maneuvers for median nerve compression should be performed in a complete examination of the hand. In cases of compression elsewhere, such as with pronator syndrome, a Tinel sign will be absent over the transverse carpal ligament but present in the proximal anterior forearm. In the event there is compression of the nerve in the distal forearm, possibly from incomplete release of the antebrachial fascia , the patient may have symptoms when tapping on the nerve in this region. If an iatrogenic injury to a branch of the median nerve is being considered, percussion five to eight centimeters proximal to the incision site may lead to the patient localizing paresthesias along the course of the injured nerve [17]. When done over the site of injury, the pain may be too much for the patient to localize. Provocative maneuvers for median nerve compression include the carpal tunnel compression test (Durkan’s test ), performed by applying manual compression over the transverse carpal ligament for 30 s. Tinel sign and the carpal tunnel compression test are both positive when paresthesias are elicited along median nerve innervation. Phalen and reverse Phalen are performed by maximal flexion (Phalen), and extension (reverse Phalen), held for 60 s to illicit numbness in the median nerve distribution [16].

A thorough physical examination as described above is performed not only for current symptoms but as a comparison for prior symptoms. It further guides the clinician toward recurrent, persistent, or new symptoms and adds to information obtained in the history. For example, thenar atrophy confirms the likelihood of chronic compression of the median nerve. A lack of change in symptoms combined without improvement symptoms post-surgery points toward an incomplete release of the transverse carpal ligament causes persistent symptoms. Pain along the third web space with percussion proximal to the incision site may indicate entrapment or iatrogenic injury of the superficial branch coming off the median nerve to the third web space [17]. Most importantly, comparison of physical exams prior to and post initial carpal tunnel release may provide notable information with regard to the presences of a symptom-free interval or an iatrogenic injury.