Ultrasound-Derived Nerve Cross-Sectional Area in Extremes of Height and Weight

BACKGROUND AND PURPOSE There is a lack of consensus in the literature as to which body habitus parameter most influences nerve cross-sectional area (CSA). This study was specifically designed to determine if height or weight is more influential. METHODS Fifteen young healthy participants, 8 extremely tall and 7 heavy, with no peripheral nerve symptoms were recruited. The tall cohort consisted of males who were 74 inches or taller and females who were 68 inches or taller. The heavy cohort consisted of males who were 274 lbs or heavier and females who were 200 lbs or heavier. Measurements were obtained bilaterally at 7 sites using neuromuscular ultrasound: median nerve at the wrist and mid-forearm, ulnar at the elbow, radial at the spiral groove, fibular at the knee, tibial at the ankle, and sural at the ankle. The nerve CSA at each site was measured by tracing of the nerve using the "freehand" trace function of the ultrasound device. RESULTS Weight tightly correlated with nerve CSA (R-2 = .69, P < .001), while height did not significantly predict CSA (R-2 = .10, P = .244). Nerve CSA for tall participants did not systematically deviate from an historical control group. Conversely, with exception of the tibial and sural nerves at the ankle, all nerve CSAs for heavy participants were higher than in the control group. CONCLUSION Weight was found to be the body habitus parameter that most influences nerve CSA. This will inform clinicians when using nerve imaging to evaluate participants at either extreme of weight.