Does BMI, Age, Gender, or Diabetes Affect Cross-Sectional Area of the Median Nerve in Asymptomatic Patients?: Level 4 Evidence

Abstract

BMI, age, gender, and diabetic status affect the baseline cross-sectional area (CSA) of the median nerve at the wrist of asymptomatic individuals. Consecutive patients without a history of carpal tunnel release were recruited. CTS-6 was completed in all patients; those with a score of 0 were included. Ultrasound examination was performed on both wrists and CSA of the median nerve at the carpal tunnel inlet recorded. Trends and differences in median nerve CSA and CTS-6 score were analyzed with regard to hand dominance, age, gender, BMI, and presence or absence of diabetes. Within each group, wrists were separated into subgroups based on hand dominance. Statistical analysis was performed using correlations and independent T-tests. A significant difference was seen between patients with BMI <30 (dominant side mean = 6.5 mm2, non-dominant side mean = 6.1 mm2) and those =30 (dominant side mean = 7.6 mm2, non-dominant side mean = 7.2 mm2). CSA correlated with BMI (dominant side r=0.30, non-dominant side r=0.35) and age (dominant side r=0.27, non-dominant side r=0.24). Side to side difference reached marginal significance (P = 0.049). Mean CSA was significantly higher in the non-dominant hand of diabetics (mean = 8.0 mm2) compared to non-diabetics (mean = 6.3 mm2, P = 0.002) but not in the dominant hand (mean = 7.9 mm2 in diabetics, mean = 6.7 mm2 in non-diabetics, P = 0.13). CSA was not significantly different with respect to gender. Females trended toward a smaller mean CSA than males for both the dominant (mean = 6.5 mm2 for females, 7.1 mm2 for males, P = 0.1) and non-dominant hands (mean = 6.4 mm2 for females, 6.5 mm2 for males, P = 0.69), though the differences did not reach statistical significance. (Table 1) •Patients who are obese have a significantly larger median nerve CSA at baseline, even in completely asymptomatic individuals.•Median nerve CSA shows a positive correlation with both BMI and age.•In a side to side comparison, CSA was larger for the dominant wrist compared to the non-dominant wrist.•Diabetics had a significantly larger median nerve CSA in the non-dominant hand but not the dominant hand.•Females trended toward a smaller mean CSA than males, but this did not reach statistical significance.