Carpal tunnel syndrome (CTS) is a common condition, with a 1% to 5% incidence in the adult population. Making an accurate diagnosis of CTS is a critical aspect of successful management and treatment because many other conditions can mimic CTS. The surgeon should not confuse a vague symptom of arm numbness with CTS.

CTS is associated with pain in the distal third of the forearm and the volar wrist area. Characteristic paresthesias occur in the median nerve distribution, involving the thumb, the index finger, the long finger, and the radial portion of the ring finger. However, this anatomic distribution may not occur if there is more proximal nerve compression, multiple nerve compression, or an innervation anomaly such as a Martin-Gruber anastomosis.

The carpal tunnel compression test, in which the examiner exerts finger pressure over the wrist and the median nerve, is useful.¹ A combination of a positive Tinel sign, the Phalen maneuver, and carpal tunnel compression, with appropriate negative aspects of the physical examination to screen for alternative conditions, has been shown to be both sensitive for and specific to CTS, as proved by electrodiagnostic testing.

Once a diagnosis of CTS has been made, nonsurgical treatment is recommended. This may include activity modification, the use of wrist braces, the use of oral nonsteroidal anti-inflammatory drugs or corticosteroids, and a trial of cortisone and local anesthetic injection into the carpal canal.

If nonsurgical treatment fails and the patient presents with significant symptoms, carpal tunnel release (CTR) should be considered. CTR has evolved over the years from a standard open procedure with a long palm and forearm incision to limited incision and endoscopic techniques. These treatments are effective, but there are also reports of complications with all of the treatments. The key objective of the surgery is to completely divide the transverse carpal ligament without injury to the nerve. It is now well established that for index CTS surgery, internal neurolysis is not considered helpful and can be deleterious. Identification and knowledge of the anatomy in this area and the ability to differentiate the median nerve from the palmaris longus and the flexor tendons are key regardless of surgical technique and are based on the surgeon’s knowledge and experience with the particular anatomy of the region affected by CTS.²

The diagnosis of CTS is confirmed by a combination of the presence of classic clinical symptoms and signs and positive nerve conduction studies (NCS) and electromyographic (EMG) studies. If the NCS or EMG findings are negative, at least one trial of corticosteroid injection should be given to evaluate the clinical response. The surgeon should confirm that a trial of nonsurgical treatment has been undertaken without a cure and also confirm that differential diagnoses have been considered.

The presence of other conditions will affect the overall results of CTS treatment; this needs to be discussed with the patient before, not after, surgery. In fact, the surgeon should strongly consider delaying CTS treatment to control or improve other conditions that may be amenable to nonsurgical treatment, such as tendinitis of the wrist, forearm, or elbow.

If the above conditions are met, CTR should have good to excellent results in more than 95% of cases.² In the case of recurrent CTS, the key to success is patient selection. Although there are scant data to correlate the preoperative evaluation with results, the patient’s clinical course and response to nonsurgical treatment along with the interpretation of electrodiagnostic studies and MRI should be carefully considered before revision surgery.

Electrodiagnostic testing can be helpful in confirming the diagnosis of CTS and potentially eliminating secondary diagnoses. The earliest signs of CTS are generally an increase in sensory and motor latency followed by an increase in distal motor latency. Sometimes, a decrease in amplitude is a soft indicator of peripheral neuropathy. The degree of delay in latency and the degree of decrease in amplitude has some rough correlation with the severity of the neuropathy. Conduction velocity can be a helpful parameter. As the velocity moves from a normal conduction velocity of 50 mps (m/s) to 60 mps down toward a conduction velocity of 30 mps, the trend is highly suggestive of peripheral neuropathy.

EMG of median nerve-innervated thenar muscles is helpful in that denervation patterns can be seen in cases of axonal degeneration with positive sharp waves and fibs highly suggestive of a chronic axonal neuropathy. The evaluation of the ulnar nerve at the wrist and the peripheral nerves across the elbow and the forearm can be also performed if there is clinical suspicion of this.

It should be noted that there is disagreement between the electrodiagnostic disciplines and the hand surgery disciplines regarding the sensitivity and the specificity of electrodiagnostic tests. It would be prudent for the physician to not use an NCS and EMG test as an initial screen for diagnosis of CTS. Rather, a careful history and physical examination should take a primary role in the diagnosis of CTS, with electrodiagnostic testing taking a secondary or supportive role in making the diagnosis. The false-positives in NCS- and EMG-diagnosed CTS derive from the fact that many of the conditions noted earlier are not particularly sensitive to electrodiagnostic testing, even if they are screened for. At the same time, there is a population of patients who exhibit all the signs and symptoms of CTS as a discrete diagnosis but have normal NCS and EMG findings, thus having a false-negative result in electrodiagnostic testing.⁵ These patients, whose histories and physical examinations have findings consistent with CTS, should be considered to have the diagnosis of CTS despite the negative electrodiagnostic studies. The surgeon should be careful to reevaluate these patients at multiple intervals if they are being treated nonsurgically and such treatment has failed, particularly if surgical treatment is being contemplated.