Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome, and is characterised by numbness and tingling of the radial 3 ½ digits. It is found in 1% of the general population1 and increased incidence is noted in women, the elderly and pregnant patients. Risk factors for development of CTS include diabetes mellitus, obesity, smoking, hypothyroidism, renal failure as well as rheumatoid arthritis.

Occupational risk factors have long been recognised and primarily include repetitive, forceful hand work with wrist extension as well as vibration, cold environment, and combinations thereof.² Workers with increased risk for CTS include workers in the construction, electronic and forestry, fish processing and cannery, frozen food/meat, furniture factory, garment and textile, and metal casting industries; aircraft mechanics; appliance and automobile manufacturers; and dentists.³

CLINICAL PRESENTATION

The classic patient is usually a lady in her fifties who complains of numbness and subjective weakness in her affected hand. Occasionally, she may also present with pain and a tingling sensation. We often ask about the occurrence of night symptoms which affects the quality of life for the patient. More often than not, both hands are affected simultaneously.

Physical examination involves looking out for signs such as abnormal sensation, Tinel’s sign, Phalen’s test, abductor pollicis brevis weakness, thenar atrophy as well as decreased grip strength. It is also important to look for previous fracture of the wrist with deformity or the presence of lumps such as ganglions or gouty tophus which can compress on the median nerve and result in CTS.

A thorough history and clinical examination is usually sufficient to make the diagnosis of CTS. It is also important to be aware that there are other potential and more proximal sites of peripheral nerve compression, such as cervical root compression, thoracic outlet compression, pronator tunnel syndrome, which can coexist with CTS, resulting in the double crush syndrome. The severity of CTS can be staged as shown in Table 1.

Table 1 Stages of clinical severity

Nerve conduction study is routinely done to confirm the diagnosis especially when the clinical features do not follow the classical presentation and when other neurologic diagnoses, in addition to or instead of CTS, are suspected. Moreover, electrodiagnostic studies can provide baseline data and exclude other pathology that presents with similar symptoms. It also aids to ascertain the severity of the disease.

High frequency ultrasound is an increasingly popular modality which may be utilised in clinching the diagnosis of CTS when the diagnosis is uncertain and the patient cannot tolerate electrodiagnostic testing. It diagnoses CTS based on the following measurements: median nerve cross-sectional area, median nerve flattening ratio and palmar displacement of the flexor retinaculum.

MRI, on the other hand, may be used for evaluation of secondary pathologies such as a mass (ganglions or lipomas) or pathologic flexor tenosynovitis. Currently, such imaging is not necessary in the workup of uncomplicated CTS.

LIKELY TREATMENT OPTIONS BY GPs

Conservative treatments such as night splints and activity modifications are widely accepted first-line therapies for mild CTS. Such splints which keep the wrist in a neutral position, help to reduce the night symptoms that occur secondary to an increased intra-canal pressure caused by inadvertent excessive flexion or extension of the wrist during sleeping. Activities resulting in overuse of the hands should be identified and cut down. However, their effects are usually temporary.

Cochrane review by O’Conner et al⁴ stated that drug therapy, including nonsteroidal anti-inflammatory medications (NSAIDs), diuretics and vitamin B6 do not have any short-term benefit when compared to placebo or control. Oral steroids, on the other hand, do have some short-term benefit.

Local corticosteroid injection into the carpal tunnel is of diagnostic and potentially therapeutic benefit. An initial positive response to the injection has been strongly correlated with a positive response to surgical release and is considered the pre-operative factor that is most predictive of outcome.

Cochrane review by Marshall et al⁵, showed that a steroid injection does provide greater clinical improvement in symptoms one month after injection compared to placebo and it also provides significantly greater clinical improvement than oral corticosteroid for up to three months. Its value relative to other nonsurgical treatments e.g. splinting has been controversial as well-controlled comparative studies are lacking, and because a prominent histological inflammatory response is not usually seen with CTS.

Although steroid injections appear to be generally safe, they are not routinely performed as studies have repeatedly shown that they rarely provide relief of symptoms beyond one year. They are also associated with several risks, including exacerbation of median nerve compression, accidental injection into the median or ulnar nerves, and digital flexor tendon rupture.

Carpal mobilisation or nerve gliding exercises may be helpful for mild to moderate symptoms when combined with other treatments such as activity modification, wrist splinting or corticosteroid injections. This set of exercises is also useful in preventing nerve adhesions post-surgery or if there has been significant trauma to the area such as a fracture that requires wrist surgery or repair near the carpal tunnel.

Figure 1 demonstrates the median nerve gliding exercises. Exercises 1 to 6 should be performed as one cycle and repeated up to five cycles with a 1-2 hour interval each day.

WHEN TO MAKE A SPECIALIST REFERRAL

The patient should be referred to a hand surgeon for surgical decompression if the non-operative options fail or as early as possible in advanced stages of nerve compression as indicated by progressive motor deficit, severe sensory deficit, or a severe electrodiagnostic abnormality to avoid further nerve damage.

In patients with secondary CTS associated with a systemic disease, treatment should be targeted at the primary disease. Consultation for diagnosis should also be considered when the diagnosis is in doubt, when conservative treatment has failed, and when surgery or other invasive treatment is being considered.

LIKELY TREATMENT OPTIONS BY SPECIALISTS

Surgical release of the carpal tunnel is indicated when conservative measures have not managed to relieve the patient’s symptoms or when the compression is severe enough to avoid any further delay which will worsen the denervation of the median nerve. It consists of division of the transverse carpal ligament, which increases the space in the carpal tunnel, thereby reducing the pressure on the median nerve.

Open carpal tunnel release (OCTR) (Figure 2) is currently the gold standard surgical procedure for treatment of this condition and is associated with a high success rate of up to 90% in many studies. It is a very safe operation that can be performed under local or regional anaesthesia (Bier’s block).

Endoscopic carpal tunnel release (ECTR) (Figure 3) has gained recognition as an alternative to OCTR. In ECTR, an endoscope and cutting instrument is inserted via a small incision at the level of wrist crease and the carpal ligament is divided under direct vision. This technique has gained in popularity over the years due to the perceived benefits of smaller scar, better post-operative comfort as well as less wound pain.

Post-surgical care includes elevation of the hand, gradual exercises of the hand, wrist and forearm. Although infrequent, complications of surgery for both endoscopic and open carpal tunnel release can still occur and are included in Table 2.⁶

Outcome studies have demonstrated that both open and endoscopic releases produce subjective improvement in pre-operative symptoms.^7-8 The choice of technique is largely surgeon-dependent. Each has its advantages and disadvantages, and each technique has a learning curve, which is greater with the endoscopic technique.

   Although outcome measures and results vary, no significant differences were found in terms of efficacy. Several randomised, controlled studies comparing various surgical techniques for CTS treatment have failed to demonstrate any strong evidence supporting the use of one technique over the other.⁹

A recent meta-analysis of 21 randomised, controlled trials comparing open versus endoscopic carpal tunnel release indicated that endoscopic release allows earlier return to work and improved strength during the early post-operative period. Results at 6 months or later were similar, except that patients undergoing endoscopic release were at greater risk for nerve injury and less risk for scar tenderness than those having open release.¹⁰

THE SINGAPORE GENERAL HOSPITAL EXPERIENCE

A prospective study conducted by the Department of Hand Surgery¹⁰, Singapore General Hospital (SGH) from 2007 to 2009 showed that all the patients experienced improvement in symptoms with 72% showing complete symptomatic relief. 74% showed improvement in function and 66% showed improvement in grip strength. 82% were either completely or very satisfied with the results of surgery. The study also found that older patients and patients with weakness associated with poorer outcomes.

Patient factors such as gender, occupation, presence of comorbidities such as diabetes mellitus, thyroid disease and rheumatoid arthritis did not appear to significantly influence the results of operation. In addition, the duration of symptoms before surgery and degree of electrophysiological severity also did not correlate with the outcomes of surgery.

The results do not imply that patients with the negative predictive factors should be discouraged from surgery. In fact, our study showed that, regardless of age, signs and symptoms, most, if not all patients, will benefit considerably from surgery.

Rather, clinicians should include these factors in their discussions with patients and inform them that the presence of these factors portend a less favourable outcome. Patients will thus have more accurate expectations of the outcomes of surgery.

CONCLUSION

Patients should be educated about the nature of CTS, its known causes and risk factors, exacerbating activities, diagnostic methods and therapeutic options. Patients who have good information about their disease will more likely exercise secondary prevention and adhere to therapeutic interventions and follow-up care. Many patients feel reassured by learning about their disease, particularly if they had suspected a more serious neurologic problem or other conditions. Primary care physicians are in the best position to educate patients and empowering themselves and thereby their patients with knowledge on this commonest entrapment neuropathy will only serve for the greater good.

GPs can call for appointments through the GP Appointment Hotline at 6321 4402.

Dr Jacqueline Tan is currently the Director of Micro-reconstruction Service and Consultant with the Department of Hand Surgery at the Singapore General Hospital. Her areas of special interests are in brachial plexus reconstruction, peripheral nerve disorders and reconstructive microsurgery of the extremities.

Dr Rebecca Lim is currently a third year SingHealth Hand Surgery Resident. Hand Surgery is her chosen specialty at the Singapore General Hospital as it is highly intricate, challenging, pushes her boundaries and trains her powers of concentration and perseverance.