The distribution of electrophysiological severity of carpal tunnel syndrome (CTS) in an outpatient setting and whether electrophysiological severity could be an objective tool for decision-making regarding choice of surgery were investigated. During conservative treatment, 1079 outpatients with idiopathic CTS were classified according to the electrophysiological severity scale (Stage 1-5). The results were provided to the patients and explained, but they were not indicated a treatment protocol intentionally. We recommended surgery to those outpatients who presented with difficulty in pinching due to severe thenar atrophy and/ or showing poor response to conservative treatment. However, the decision-making of surgical or nonsurgical treatment remained with patients. In the distribution of severity stages, Stage 4 was the most common (34%). Two hands were not classifiable. Surgery was chosen in 443 of 1077 hands (41.1%): The operation selection rate increased with severity of the stage and the patients with Stage 5 showed the greatest preference among Stage 1-5 (p<0.0001). This was shown in both female and male groups in gender analysis, and in both ≤ 69 y.o. and ≥70 y.o. groups in the age analysis. There was no significant difference between female and male hands, and ≤ 69 y.o. and ≥70 y.o. hands. Among varied reasons for the decision-making process for surgical treatment in CTS, electrophysiological severity scale plays an important role as an objective tool without being influenced by subjective elements; gender and age
