title: Reasons for using swelling ratio in sonographic diagnosis of carpal tunnel syndrome and a reliable method for its calculation.
abstract: BACKGROUND
  The aim of this study was to investigate factors affecting median nerve cross-sectional area (CSA) and determine a dependable swelling ratio (SR) calculation method.
  
  
  METHODS
  Using ultrasonography, median nerve CSAs were measured at the tunnel inlet, midtunnel, and outlet, and at 4 cm and 12 cm proximal to the wrist. We used CSAmax as the largest of the tunnel measurements and calculated swelling ratios (SRs) by using the CSAmax. Sonographic measurements were correlated with electrophysiologic findings. We evaluated the effects of gender, weight, and height on median nerve thickness.
  
  
  RESULTS
  We studied 95 wrists of 55 CTS patients and 48 wrists of 27 volunteers. Gender, weight, and height had effects on certain median nerve CSA measurements. CSAmax, SRmax4, and SRmax12 had superior correlations with electrophysiologic findings. The correlation between 4-cm and 12-cm median nerve CSAs was statistically significant (r = 0.879 and P < 0,001).
  
  
  CONCLUSIONS
  We have developed a reliable SR method considering factors affecting median nerve CSA.
authors.affiliation: Second Department of Physical Medicine and Rehabilitation, Ankara Education and Research Hospital, Ankara, Turkey. alperulasli@yahoo.com
authors.forename: Alper Murat
authors.initials: AM
authors.lastname: Ulaşli
authors.forename: Mahmut
authors.initials: M
authors.lastname: Duymuş
authors.forename: Bariş
authors.initials: B
authors.lastname: Nacir
authors.forename: Hatice
authors.initials: H
authors.lastname: Rana Erdem
authors.forename: Uğur
authors.initials: U
authors.lastname: Koşar
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002349:Carpal Tunnel Syndrome / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D003710:Demography; D004487:Edema / Q000000981:diagnostic imaging*; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012015:Reference Standards; D015203:Reproducibility of Results; D012727:Sex Characteristics; D014463:Ultrasonography