Asymptomatic carpal tunnel syndrome in obese and overweight patients with metabolic syndrome.

C tunnel syndrome (CTS) is the most frequent type of compressive neuropathy. It results from the entrapment of the median nerve at the level of the carpal tunnel. The most important independent risk factors are female gender, obesity, square wrists, rheumatoid arthritis, diabetes, wrist fracture, and hypothyroidism.1 The diagnosis of CTS is based on a collection of clinical symptoms and signs including pain and numbness in the territory of the median nerve in the hand, and electrophysiological findings. The clinical significance of asymptomatic electrophysiological (E)-CTS is its ability to change into the symptomatic type due to the vulnerability of the median nerve. Balci and Utku2 reported that metabolic syndrome is 3 times more prevalent in patients with CTS, and CTS is more severe when compared with cases without metabolic syndrome. Azizi et al3 reported that the unadjusted prevalence of metabolic syndrome in their study was 30% in Iran. There are different definitions for metabolic syndrome, however, it was reported by the WHO in 1999 for the first time. A European group developed a modified version in the same year, but 2 years later the United States National Cholesterol Education Program Adult Treatment Panel (ATP-III) reported simple criteria for defining metabolic syndrome and a revised version was reported in 2005.4 The aim of this study is to investigate the frequency of asymptomatic E-CTS among obese and overweight patients with metabolic syndrome and compare the severity of CTS in those groups of an Iranian population. Patient selection. After obtaining institutional ethics committee approval, we conducted a case-control study from June 2010 to November 2011 at the Zahedan University of Medical Sciences, Zahedan, Iran. We studied a local population in the southeastern province of Iran. Eighty patients with functional pain and a confirmed diagnosis of obese metabolic syndrome (body mass index [BMI] >30), and 59 cases with functional pain and overweight metabolic syndrome (BMI: 25-30) entered into the study consecutively. The diagnosis of metabolic syndrome was based on a revised version of the ATP-III, which was released by the International Diabetes Federation in 2005.4 Patients with functional pain did not have clinical criteria for referred, radicular or mechanical pain. In this situation, patients did not complain of any radiation from the neck or any neural (median or ulnar) territory pain; however, nonspecific musculoskeletal complaints were occasional. Patients with osteoarthritis, disc herniation, fractures and radiculopathies were not included in the study. Routine neurological and rheumatological examinations did not reveal any abnormal findings. The researcher explained the nature of the work, and after obtaining informed consent for the study, the examiner filled out a questionnaire on the demographic characteristics of the participants such as age, gender, occupation, any associated disorder like pregnancy, diabetes, trauma, and fractured wrists. The patients had no history or clinical signs suggesting systemic disease, and no clinical and/ or electrophysiological signs suggesting pathological conditions such as polyneuropathy, radiculopathy, weakness or atrophy of muscles or previous median nerve surgery. Electrophysiological study. The diagnosis of E-CTS was based on previously validated electrodiagnostic criteria according to the American Academy of Neurology (AAN) consisting of neurographic evidence of slowing of distal median nerve conduction. One of the researchers carried out all electrodiagnostic studies with a Medtronic-Keypoint® 4 apparatus (Medtronic A/S, Skovlunde, Denmark) on subjects lying on a bed in a quiet and warm room. All studies were carried out in the same room and in similar temperature using a surface temperature recorder. All nerve stimulations were delivered with a constant current standard bipolar surface stimulator (cathode distal). The sweep speed was set at 2 ms/division and the recording of the median nerve compound muscle action potential (CMAP) was performed using a standard bar electrode supplied by the equipment, which was placed on the thenar muscle at a distance of 8 cm from the stimulator. The CMAP for the median nerve had been measured from the baseline to the negative peak. The interelectrode distance (between active and reference electrodes) was 4 cm. Supramaximal stimulation was used for motor conduction studies, while up to 50 mA stimulation intensity was delivered for sensory nerves. The obtained sensory responses were averaged. Maximum antidromic sensory conduction