Patients with Raynaud’s disease or phenomenon may have intermittent numbness in the hands typically precipitated by stress or cold. The typical “red-white-blue” discoloration accompanies the numbness which occurs following vasospasm of the small vessels. Although history is generally enough to differentiate CTS from Raynaud’s, the results of various provocative tests and/or laboratory studies in the setting of phenomenon may be useful. Vascular insufficiency with occlusion of the radial or ulnar artery leading may mimic CTS [13]. An Allen’s test may be performed to assess for vascular competency (Figs. 14.3, 14.4, and 14.5).

The surgeon must consider additional sites of compression of the nerve proximally. The nerve may be compressed more proximally such as in the forearm with pronator syndrome. In pronator syndrome, the patient may have symptoms of weakness in the FDP of the index and the FPL and commonly has numbness in the “palmar triangle” related to involvement of the palmar cutaneous branch of the median nerve [9]. In addition, proximal lesions in the cervical spine can be problematic [9]. The patient may have isolated proximal compression or may suffer from both CTS and a proximal lesion leading to the “double-crush” phenomenon. Patients may also suffer from generalized peripheral neuropathy, and referral to a neurologist for evaluation and possible treatment may be beneficial. Electrodiagnostic testing is helpful to determine the level of pathology and to determine the presence of generalized neuropathy.

A study by Witt and Stevens reviewed 12 patients with a diagnosis of CTS who underwent unsuccessful CTR that were evaluated in their electrodiagnostic lab [16]. In their series, ten patients did not meet electrodiagnostic criteria for CTS but were discovered to have a neurological diagnosis including polyneuropathy (five patients), motor neuron disease/ALS (four), cervical radiculopathy (three), multiple sclerosis (two), cervical spondylotic myelopathy (one), and syringomyelia (one). Only one patient had severe recurrent CTS related to postoperative scarring, and one patient had asymptomatic median neuropathy at the wrist. The authors conclude that the patients either did not have CTS or their CTS were not a clinically important factor compared to their other neurologic diseases.

The surgeon should request the operative report from the patient’s index procedure, including initial workup testing such as electrodiagnostic testing , and clinical examination documentation as well as any imaging studies. Review of these documents may provide a clue as to the cause of the recurrent symptoms. Clinical exam may show misplaced or small surgical scar. MRI or ultrasound, although rarely indicated, may be used in an appropriate setting to search for an occult mass or space occupying lesion which may be the culprit of ongoing symptoms and would be an important finding not to be missed. MRI, however, does not reliably detect evidence of incomplete release [3].

A reasonable course of nonoperative management is indicated initially including splinting, rest, injections, hand therapy, and desensitization [9]. An excellent diagnostic and potentially therapeutic intervention is carpal tunnel injection. If patients exhibit improvement following injection, the recurrent carpal tunnel syndrome is likely a cause or the cause of recurrent symptoms. If these measures fail to provide adequate relief and electrodiagnostic results worsen, the surgeon can reasonably proceed to revision CTR. The patient should be counseled that they may not get relief of symptoms if the nerve was adequately decompressed initially and if recurrent carpal tunnel syndrome is not the cause of their symptoms.

The surgeon may consider using an extended carpal tunnel approach in the revision setting in order to fully assess the nerve. The surgeon should take care to document the integrity of the transverse carpal ligament at the time of repeat exploration, the integrity of the median nerve and its branches, as well as the presence of inflamed or hypertrophied synovium . The surgeon should consider sending tissue samples for pathology and culture if there are any concerns at the time of surgery as atypical or fungal infections may present with hypertrophied synovium leading to CTS [18]. The median nerve is typically contained within dense scar tissue and may require careful external neurolysis or even epineurectomy, although internal neurolysis is contraindicated [9].

Controversy exists as to whether additional tissue coverage steps should be taken in the revision setting. Some advocate that if a definitive cause for the patient’s symptoms is found, coverage may not be indicated [9]. However, if the nerve is found in significant scar tissue, it is reasonable to consider interposition of some type of soft tissue between the nerve and the residual TCL and the palmar skin to prevent recurrence. Local flap options include muscle (abductor digiti minimi, pronator quadratus, palmaris brevis), hypothenar fat pad flap, synovial flap, dermal graft, or use of synthetic membrane [9]. Distal flap options described include omental, reverse radial forearm adipofascial and small free muscle and fascial flaps [9]. In the authors’ hands, flap coverage is rarely necessary, and we feel it may contribute to additional recurrent scarring.

Outcomes following revision CTR may not be as rewarding as in the primary setting with some studies reporting poor results and up to 95% of patients reporting persisting symptoms, while others report an overall 95% satisfaction rate [3]. A recent large series reviewing results of CTS revision found that most patients demonstrate good outcomes with reasonable improvements in pain and strength [10].

Nerve injury or transection at the time of surgery is a dreaded complication but can occur even in the hands of experienced surgeons [6, 8, 9, 19]. Multiple studies including a recent meta-analysis have shown an increased risk of nerve injury in endoscopic compared to open technique; however, the nerve injuries tend to be temporary neurapraxias [4, 15]. In the next section, we explore the various nerve injuries that can be associated with CTR.

Patients will typically report a history of persistent or worsening symptoms postoperatively. Thorough examination to determine level of nerve injury should be performed. Examination should document two-point discrimination for all digital nerves as well as the distribution of the palmar cutaneous branch. The examiner should evaluate for a Tinel’s at the wrist, at the scar, as well as proximally in the forearm. This can help determine the presence of a neuroma or of a proximal nerve entrapment. Motor strength should be carefully examined to help determine level of injury. A clue to nerve damage is that patients may experience worsening postoperative pain secondary to nerve injury or transection. Relief of symptoms with injection of local anesthetic at the site of presumed injury has been described as a reliable diagnostic test [11].

Injury to the recurrent thenar motor branch has been reported as 0.01% [6]. Loss of thenar branch function leads to weakness of thumb abduction and apposition. Care should be taken to determine if the functional deficits are due to nerve injury or preexisting atrophy due to long-standing carpal tunnel syndrome [6]. Three variations of the course of the thenar branch have commonly been described and include the extraligamentous, subligamentous, and transligamentous course [20]. Extraligamentous type will arise distal to the transverse carpal ligament (TCL ) and runs retrograde to reach the thenar musculature. Subligamentous type arises from within the carpal tunnel and runs deep to the TCL until it reaches the thenar muscles. The preligamentous type branches proximal to the carpal tunnel and runs superficial to the TCL into the thenars. A recent prospective clinical study showed the presence of hypertrophic muscle overlying the TCL in all cases of sub- and preligamentous course, noting that the motor branch ran within the hypertrophic muscle [21]. Hypertrophic muscle superficial to the TCL should be incised with care, staying along its ulnar border to avoid injury to the thenar motor branch. Surgeon awareness of these variable patterns can help decrease risk of injury. A cadaveric analysis found the average distance from the distal TCL to the thenar motor branch was 6.9 ± 0.4 mm [22].

Injury to the median nerve has been reported at 0.06% [19]. Complete transection following endoscopic and open release has been reported [23] (Fig. 14.6a–c). The nerve is the most superficial structure within the carpal tunnel, typically lying radially, and may be injured with CTR. The nerve is mixed motor and sensory; therefore, patients may have a variable exam depending on the extent of partial vs complete injury [6]. Injury to the ulnar nerve has been reported with an incidence in some series of 0.03% [19]. Causes of injury to the ulnar nerve include a neurapraxia from excessive traction from the carpal tunnel retractor, laceration, or even transection from the wrong tunnel released. The ulnar nerve lies superficial to the transverse carpal ligament within Guyon’s canal, and misidentification of the carpal tunnel could lead to inadvertent ulnar nerve injury en route to the transverse ligament. Injury to the deep motor branch of the ulnar nerve leads to loss of intrinsic function including the ulnar two lumbricals, dorsal and palmar interossei, abductor digiti minimi, opponens digiti minimi, and flexor digit minimi [6]. Injury to the common digital nerve to the long and ring finger has been reported, especially following endoscopic release [9].