Carpal tunnel syndrome is a bilateral disorder, The

carpal tunnel syndrome is a bilateral disorder, The

Bagatur, A E

We studied, retrospectively, 131 patients who had undergone an open operation for the carpal

tunnel syndrome (CTS) in 229 hands. The symptoms were present on both sides in 59% of patients when first seen. Neurophysiological impairment of the median nerve was observed in 66% of the asymptomatic hands, and 73% of patients in this group developed symptoms of CTS after the opposite side had been operated on. Follow-up of patients with unilateral CTS showed that the subsequent development of disease in the unaffected hand is very common. We conclude that CTS is a bilateral disorder and that it becomes more evident as time passes. There is a correlation between the duration of symptoms and bilateral occurrence.

J Bone Joint Surg [Br] 2001;83-B:655-8.

Received 17 May 2000; Accepted after revision 13 December 2000

Bilateral presentation, or the subsequent development of symptoms in the unaffected hand, is common in the carpal tunnel syndrome (CTS). Symptoms are usually more severe on one side and sometimes treatment of one hand may lead to the aggravation or development of problems in the other. In recent publications, the incidence of bilateral symptoms has been reported to be between 60% and 87%.1,2 Although it is widely known that patients with CTS often complain of bilateral symptoms,3 there are only two studies in which this condition has been investigated in idiopathic CTS.2,4

We have therefore studied, retrospectively, the records of all our patients with idiopathic CTS who underwent open carpal tunnel release to evaluate the incidence of bilateral symptoms, the correlation between the duration of symptoms and the occurrence of bilateral CTS, the neurophysiological status, the incidence of the subsequent development of the syndrome, and the frequency of operations in initially asymptomatic hands in patients with unilateral symptoms.

Patients and Methods

We reviewed the records of all patients with CTS who had undergone open carpal tunnel release by the same surgeon (AEB) between 1992 and 2000. From an initial group of 219 patients, in whom CTS has been established both clinically and electrophysiologically, 131 (112 women and 19 men) with a mean age of 48.7 years (33 to 69) were selected for this study. The inclusion criteria were an unknown aetiology, positive electrodiagnostic tests, and a postoperative follow-up of at least 18 months. Exclusion criteria included underlying disease such as rheumatoid arthritis, diabetes, gout and hypothyroidism, as well as renal dialysis, pregnancy, space-occupying lesions such as a ganglion, previous carpal tunnel release, previous fracture of the distal radius and non-surgical treatment.

All patients had a physical examination and electrodiagnostic tests of both hands regardless of their complaints. The clinical diagnosis of CTS was based on a history of nocturnal pain and paraesthesiae, activity-related pain, a sensory deficit in the territory of the median nerve, loss of hand-grip strength, atrophy of the thenar muscles, a positive Phalen’s test, and a positive Tinel’s sign5 (Table I). Electrodiagnostic tests included needle electromyography (EMG) and nerve-conduction studies, with measurement of the distal motor latency (DML) and sensory nerve conduction velocity (SNCV) from the first and third digits to the wrist. Since the neurological symptoms of CTS are not specific for median neuropathy at the wrist, EMG studies of both hands included the distribution of the ulnar as well as of the median nerves; both DML and SNCV studies were carried out in order to exclude patients with proximal median neuropathy, polyneuropathy, or cervical radiculopathy.1,6 The temperature of the arm was not measured. All the tests were conducted in normal clinical settings at room temperature. A DML of less than 4.0 ms, a first digit-towrist SNCV of 42 m/s and a third digit-to-wrist SNCV of 44 m/s were accepted as normal.7 Pathological findings on

EMG included fibrillation activity, decreased recruitment and abnormalities in the configuration of the motor unit action potential (MUAP).1

Initially, 77 patients (59%) described bilateral and 54 (41%) unilateral symptoms of CTS. Details of the distribution of symptoms are given in Table II. Although the patients were not very accurate about the timing of their symptoms, those with bilateral problems reported a duration of about three years and those with unilateral complaints of about one year.


Electrodiagnostic tests revealed positive results in both hands in all of the 77 patients who had bilateral symptoms. When hands were affected unequally, the results were more abnormal on the worst side. In the more severely affected hands, nine patients showed an absence of at least one digit-to-wrist sensory nerve action potential (SNAP) with one also showing an absence of the motor response (Table III).

Of the 54 patients with unilateral symptoms, electrodiagnostic tests were positive in all of the symptomatic, and in 31 of the asymptomatic hands (57%) with greater abnormality in those with symptoms. In the 23 patients (43%) with negative electrodiagnostic results in the contralateral asymptomatic hands, the readings were at the upper limits of normal. None of these patients in the group with unilateral symptoms had an absence of either the digit-to-wrist SNAP or of the motor response in either hand (Table III).

EMG showed positive results only in patients with moderate or severe symptoms. In mild cases in which no pathological DML was detected, the EMG was normal. The results of the EMG studies are summarised in Table IV.

At operation the carpal tunnel was released by an open technique. When bilateral symptoms were present the more severely affected hand was treated first. Of the 77 patients who had bilateral symptoms, 45 (58%) had release of the second side within six months. Thus 32 (42%) did not, and these reported that “they were doing all right” and did not want an operation on the contralateral side. After a mean of 2.1 years, however, 21 patients (66%) with aggravated symptoms returned for operation on the other hand. The remaining 11 (34%) were contacted and reported that their symptoms either had not changed or were worse in the nonoperated hand, but that they were happy with the results of the operation on their worse hand. They did not want an operation on their contralateral hand because, with their dominant hand symptom-free, they managed better. Four of these patients had had activity-related pain initially and all had had the operation on their dominant hands; five patients were discouraged because of postoperative pain and tenderness of the scar.

Of the 54 patients in the group with unilateral symptoms, 41 (76%) developed symptoms in the non-operated hand after a mean interval of 3.2 years. Of these, 32 (78%) had a carpal tunnel release in their second hand, but the remaining nine patients did not seek a further operation. Since 27 of these 41 patients (66%) had positive nerve-conduction results before the first operation, repeat electrodiagnostic tests were not required. The two patients who had positive EMG studies in their asymptomatic hands initially were in this group. Second electrodiagnostic tests were carried out in the remaining 14 patients who had negative findings initially and all but one had neurophysiological impairment of the median nerve. EMG showed positive results in four patients. When compared with the initial results, the development of neurophysiological impairment of the median nerve with time was evident (Table V).

Electrodiagnostic tests were obtained in seven of the 13 patients who did not present with symptoms in their nonoperated hand. Three of these had positive results (mean DML of 4.4 ms, a mean SNCV first digit-to-wrist of 38.9 m/s, and third digit-to-wrist of 39.5 m/s). None of the patients in this group had positive EMG findings.


Although it is widely known that patients with CTS usually complain of bilateral symptoms, so far only two studies have specifically investigated this condition. 2,4 The authors focused on the initial incidence of bilateral symptoms and neurophysiological impairment, not on subsequent developments. In recent publications, the incidence of bilateral symptoms has been reported to be between 60% and 87%, 12 and was 59% at the first visit in our study.

In our group with unilateral symptoms, more than half had positive electrodiagnostic test results in the asymptomatic, contralateral hand. Likewise, Corwin and Kasdan 6 using electrodiagnosis, reported that median neuropathy at the wrist may occur in asymptomatic individuals. Bendler et al4 also found that 38% of the patients in their series who complained only of unilateral symptoms were shown to have bilateral neurophysiological impairment of the median nerve. Padua et al2 found similar circumstances in about half of the asymptomatic hands.

In those with bilateral symptoms and in those affected unilaterally, 14% and 26%, respectively, remained with surgery to one hand only after a mean of 3.6 years from the first operation. All of the patients in the first, and half of the patients in the second group, had postive electrodiagnostic test results in these non-operated hands. If the patients with an established diagnosis are excluded, there was only one who was symptomatic, but had negative electrodiagnostic results, whereas 13 had positive findings. The suggests that the remaining patients will also develop neurophysiological impairment of the median nerve in the course of time, becoming symptomatic and requiring treatment.

The results of nerve-condition studies were worse in patients with bilateral symptoms than in those with unilateral problems, and there were no patients with absence of the SNAP or of the motor response in the latter group. EMG also gave less positive results even in the symptomatic hands of the group with unilateral symptoms. Furthermore, in the group with bilateral symptoms, patients who had more severe symptoms in one hand had worse results on nerve-conduction studies compared with patients with symptoms of equal severity in both hands. It was also noted that patients with absence of the SNAP or of the motor response were also in the first group. This is probably because CTS usually starts in one limb, and affects the other later. The first affected hand always has the worse symptoms and more severe neurophysiological impairment.

Patients were not very certain as to the duration of their symptoms. Those with bilateral complaints reported that they had had these for about three years, while in patients with unilateral symptoms the duration was about one year at the time of the first visit. Since patients in the latter group developed symptoms in the contralateral hand with time, we assume that bilaterality may be time-dependent. Unfortunately, the records were not very precise about the duration of symptoms, so that a definite conclusion could not be drawn. A prospective study design as recommended by the American Association of Electrodiagnostic Medicine would allow the uniform collection and analysis of data.1

Nakamichi and Tachibana reported an increased incidence of space-occupying lesions in unilateral compared with bilateral CTS and concluded that when the condition is unilateral and the aetiology is not clear, a space-occupying lesion should be suspected. In our series, five of the patients excluded for having a space-occupying lesion had unilateral CTS. Although these patients were not included in the study, the unilateral presentation implies the bilateral nature of idiopathic CTS.

We suggest that CTS is a bilateral disorder and that this is confirmed with the passage of time. There is a correlation between the duration of symptoms and bilateral occurrence of CTS. We believe that patients with unilateral symptoms should be closely monitored, both clinically and, if possible, neurophysiologically, and warned about the likelihood of the development of the disease in their asymptomatic hands. Prospective, rather than retrospective, studies should be carried out to establish this hypothesis further.

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.


1. Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH. Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. AAEM Quality Assurance Committee. Muscle Nerve 1993;16:1392-414.

2. Padua L, Padua R, Nazzaro M, Tonali P. Incidence of bilateral symptoms in carpal tunnel syndrome. J Hand Surg [Br] 1998;23:603-6.

3. Kulick RG. Carpal tunnel syndrome. Orthop Clin North Am 1996;27:345-54.

4. Bendler EM, Greenspun B, Yu J, Erdman WJ 3rd. The bilaterality of carpal tunnel syndrome. Arch Phys Med Rehabil 1977;58:362-4.

5. Davis TRC. Diagnostic criteria for upper limb disorders in epidemiological studies. J Hand Surg [Br] 1998;23:567-9.

6. Corwin HM, Kasdan ML. Electrodiagnostic reports of median neuropathy at the wrist. J Hand Surg [Am] 1998;23:55-7.

7. Aulisa L, Tamburrelli F, Padua R, et al. Car-pal tunnel syndrome: indication for surgical treatment based on electrophysiologic study. J Hand Surg [Am] 1998;23:687-91.

8. Nakamichi K, Tachibana S. Unilateral carpal tunnel syndrome and space-occupying lesions. J Hand Surg 1993;18:748-9.

A. E. Bagatur, G. Zorer

From SSK Istanbul Training Hospital, Turkey

A. E. Bagatur, MD, Orthopaedic Surgeon G. Zorer, MD, Associate Professor of Orthopaedic Surgery Department of Orthopaedic Surgery and Traumatology, SSK Istanbul Training Hospital, Kocamustafapasa 34310, Istanbul, Turkey.

Correspondence should be sent to Dr A. E. Bagatur at Funda 07-01, No. 37, Bahcesehir 34850, Istanbul, Turkey.

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