Catechol-O-methyltransferase Val158Met polymorphism is associated with pain and disability, but not widespread pressure pain sensitivity, in women with carpal Tunnel syndrome.

BACKGROUND: The genetic influence of Val158Met polymorphisms, one of the potential genetic determinants for nociceptive processing, has not been previously investigated in women with carpal tunnel syndrome (CTS). OBJECTIVES: To investigate the association between the Val158Met polymorphism with CTS and to assess the relationship between the Val158Met polymorphism and the clinical outcomes and widespread pressure pain hypersensitivity in women with CTS. STUDY DESIGN: Case control study. SETTING: Neurology department at an urban hospital. METHOD: One hundred nine (n = 109) women (mean age: 47 ± 9 years) with a clinical and electrodiagnostic diagnosis of CTS and 109 matched healthy women participated. After amplifying the Val158Met polymorphism by polymerase chain reactions, rs4680 genotype frequencies and allele distributions were calculated. We classified individuals according to their Val158Met polymorphism: Val/Val, Val/Met, Met/Met. The intensity of the pain was assessed with a numeric rating scale (0-10) and disability was determined with the Boston Carpal Tunnel Questionnaire. Pressure pain thresholds were bilaterally assessed over median, radial, and ulnar nerve trunks; C5-C6 facet joints; and carpal tunnel and tibialis anterior muscles.Institutional Review Board: The study project was approved by the local human research committee (HUFA-12/14). All participants signed an informed consent prior to their inclusion in the study. RESULTS: The distribution of the 3 Val158Met genotypes (Val/Val, Val/Met, Met/Met) and alleles was not significantly different between women with CTS and healthy women (Chi-Square = 0.498; P = 0.780). Women with CTS carrying the Met/Met genotype showed higher levels of pain and disability than those with the Val/Met genotype (P < 0.01) and with the Val/Val genotype (P < 0.001). No differences in the years with pain (P = 0.954), age (P = 0.740), depression (P = 0.530), severity of CTS (P = 0.744) or presence of unilateral-bilateral symptoms (P = 0.279) existed depending on the rs4680 Val158Met genotype. No significant differences in widespread pressure pain sensitivity were observed in any of the points depending on the rs4680 Val158Met genotype (P > 0.315). LIMITATIONS: We only recruited women from a specialized department. CONCLUSION: Current results indicated that the Val158Met polymorphism seems not to be a risk factor for the development of CTS; however, it was associated with increased perception of pain and higher disability scores.