Impact of foot sole insensitivity and reduced nerve conduction velocity on postural control and functional gait

Peripheral neuropathy is characterized by decreased foot sole sensitivity and slowed nerve conduction velocity, leading to impaired postural control and functional gait performance. This study assessed the differential effects of reduced foot sole sensitivity and slowed nerve conduction velocity on postural control and functional gait. Thirty-five participants were evaluated for two main clinical symptoms: the H-index and foot sole sensitivity. Two times the square of the height (H) of the individual divided by the latency (T) between the onsets of the M- and H-waves of the H-reflex were used to calculate the H-index (2 × [H/T]2). Foot sole sensitivity was evaluated using a monofilament on five sites at the bottom of the foot. Participants were categorized into three symptomological groups: (i) less affected (LA), (ii) moderately affected (MA), and (iii) severely affected (SA), based on their H-index ranges of 78.0 – 109.4, 42.8 – 76.6, and 45.6 – 75.5 cm2/ms2, respectively, and foot sole sensitivity score ranges of 6 – 10, 6 – 10, and 0 – 5, respectively. Outcome variables included center of pressure (COP) standard deviation in the anteroposterior direction and COP average velocity (Vavg) during 30 s of eyes-open quiet standing, as well as 6-min walk distance (6MWD) and timed-up-and-go duration (TUG). Multivariate analysis revealed significant group differences (P < 0.05), with post hoc analysis showing significant differences between LA and SA in Vavg (F4,30 = 3.752; P = 0.014). Discriminant analysis revealed Vavg as the primary determinant, while 6MWD and TUG were secondary determinants of group separation. Notably, enhanced functional gait was associated solely with sensitive foot soles and heightened nerve conduction velocity within the LA group, not in the MA or SA groups. Disease severity mediated the specific effects on postural control and functional gait, underscoring the importance of tailoring rehabilitation protocols to address individual symptoms.