Statistics from Altmetric.com
Recently, Cimmino et al 1 reported an epidemiological survey on the prevalence of carpal tunnel syndrome (CTS) in patients with fibromyalgia syndrome (FM). These authors found that 9.7% of 93 patients studied after mailing a questionaire had both CTS and FM, suggesting an association between them and that there were possible similarities in the aetiopathological mechanisms.
Cimmino et al referred to our previous report on CTS and FM2 in which we observed 33 patients with CTS in a group of 206 consecutive FM patients (16%), and they suggest that this 16% means that underlaying mechanisms may be common for CTS and FM.
We cannot agree with this suggestion. Our study was not controlled, but no statistically significant differences could be appreciated in the prevalence of CTS in FM women (29 of 191) from our series with that in general population women reported by de Krom et al (35 of 340).3 On the other hand, we noticed that CTS had been overlooked in 27 of 191 (14.1%) women with FM in our series despite mean duration of CTS symptoms of 8.1 years (range 6 months to 15 years)2 while only 23 of 340 (6.7%) women with CTS did not have a previous diagnosis of CTS in the series of de Krom et al.3
Both studies are probably biased. In our study, patients with FM and CTS would complain about more severe symptoms and were referred to a rheumatology unit, and thus CTS prevalence could be overestimated in this sample. As pain and paresthesia in the hands are common complaints in patients with FM, CTS was overlooked before rheumatological consultation. Recently, we have carried out studies that may highlight these points: firstly, we have observed that patients referred for rheumatological consultation often have multiple diagnosis at discharge (38%) that explain the musculoskeletal symptoms of the patient.4 Patients with both CTS and FM had never had a diagnostic suspicion of both diseases previous to rheumatological consultation. In another study of the clinical characteristics of 173 patients with idiopathic CTS (diagnosis was based on neurophysiological studies in all cases),5 CTS was commonly bilateral and severe, and most patients had been referred with a diagnosis of ‘arthritis’. Again, the prevalence of FM and CTS was high (19%) and patients with FM had significantly more severe CTS than patients without FM. Presence of associated musculoskeletal conditions in a given patient or bilateral CTS involvement seem to act as confounding symptoms for correct diagnosis before rheumatological consultation.
In the study of Cimmino et al, 2440 of 4456 (54%) of the subjects returned the questionaire, 182 of 2440 (7.2%) met criteria for clinical examination, and 93 of 182 (51.1%) agreed to be visited. One would expect that patients with both conditions would be more prone to answer the questionaire and accept consultation.
In conclusion, at the present time, it cannot be stated that CTS is more frequent in patients with FM than in the general population, and common pathogenic mechanisms should not be proposed. Nevertheless, it is clear that CTS is often overlooked or misdiagnosed in patients showing atypical symptoms such as bilateral, severe CTS, or associated FM before rheumatological consultation. In addition, we feel that rheumatologists should be alert to the possibility of associated CTS and FM, which is probably more frequent in patients referred to rheumatology units than the 2.4% previously reported in a retrospective series.6
Perez-Ruiz and colleagues raise several interesting points on the relation between fibromyalgia (FM) and carpal tunnel syndrome (CTS). The first point is that in their original paper1 no significant difference in the prevalence of CTS was found between Spanish women with FM (15.1%) and a general population of Dutch women (10.2%).1-2 However, we feel that comparing populations from different geographical areas may be misleading because environmental and social differences may modulate perception of pain. In fact, data from the US 1988 National Health Interview Survey report a prevalence of self diagnosed CTS of 1.55%.1-3 To verify the null hypothesis on the association between CTS and FM, a well conducted epidemiological study should be performed in the general population of a single geographical area.
Our previous study was not specifically devised to consider this point. It acknowledged that the insufficient response to the questionnaire could have biased the results toward an over-representation of the association FM-CTS.1-4 The postal questionnaire we used was developed to identify patients with rheumatoid arthritis. We were surprised to find that a considerable proportion of the patients who answered positively to this questionnaire were in fact affected by a combination of FM and CTS.1-4 Also Perez-Ruiz et al noted that patients attending a rheumatology clinic occasionally show multiple manifestations mimicking inflammatory conditions. In addition, in another abstract, Perez-Ruiz et al report that 19% of patients with CTS have FM and that CTS is more severe in this subgroup. This finding would further support the hypothesis of a common pathogenetic link between the two conditions.
Finally, we agree with Perez-Ruiz et al that patients with FM commonly report paresthesia and pain in their hands. In our experience, FM patients not only often describe paresthesia and pain in the area innervated by the median nerve but also present pain and numbness elicited by specific manoeuvers.
However, results of electrodiagnostic studies are often negative in FM. A possible explanation is that the median nerve may be involved in FM in a milder degree than in classic CTS. In this setting, electrodiagnostic tests may show a poor sensitivity.
These similarities between FM and CTS give the impression of an association of these conditions. To elucidate whether FM and CTS are really associated, we are presently comparing the electrodiagnostic findings as well as the appearance of the median nerve and of the carpal tunnel by ultrasonography and dedicated extremity magnetic resonance in patients with pure CTS or with the presumptive association FM-CTS.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.