A comparison of balance control during stance and gait in patients with inflammatory and non-inflammatory polyneuropathy

Abstract

Introduction: We compared changes in balance control due to chronic inflammatory demyelinating polyneuropathy (CIDP) and non-inflammatory (non-inf) polyneuropathy (PNP) to each other and with respect to healthy controls (HCs). Differences in patients' subjective impressions of balance capabilities were also compared.

Methods: Balance control of 11 CIDP patients (mean age 61.1±(sd) 11, 8 male) and 10 non-inf PNP patients (mean age 68.5±11.7, all male) was examined and compared to that of 18 age- and gender-matched healthy controls. Balance control during stance and gait tasks was measured as trunk sway angles and angular velocities with body-worn gyroscopes. Patients' subjective impressions of balance were obtained using the Dizziness Handicap Inventory (DHI). The Neuropathy Impairment Score in the Lower Limbs (NIS-LL) was used to measure clinical disease status.

Results: Non-inf PNP patients had slightly lower NIS-LL (13.5±7.2 vs. 17.9±15.1) and DHI scores (22.6±17.1 vs 27.6±16.3). Gait tasks showed a significant decrease in gait speed with respect to HCs for both patient groups but reduced trunk sway for non-inf PNP patients. Trunk sway during tandem walking and walking on the heels was greater for both groups than that of HCs. Sway during 2-legged stance tasks with eyes closed on a firm or foam surface was also greater than for HCs.

Discussion: Compared to HCs both groups of patients have significantly greater sway for most stance and gait tasks accompanied by reduced gait speed. As for HCs, non-inf PNP patients reduced trunk sway with slower gait speed. In CIDP patients this compensatory strategy was absent, possibly due to a greater deficit of efferent and motor nerve fibers. An interpretation of these findings is that CIDP patients have reduced ability to decrease trunk sway with slower gait speed and is possibly associated with an increased risk of falls.

Fig 1. Examples of pitch and roll trunk sway during walking 8m with eyes open for a typical CIDP and a non-inf PNP patient.

The upper traces are the time plots with the 8m measurement sequence marked with vertical lines indicating when the subject passed light barriers spaced 8m apart. The lower x-y plots are of pitch versus roll velocity over the 8m walking interval. The envelope of the angular velocity excursions is presented as a convex hull around each x-y plot. As indicated, both subjects are of the same age and walk with similar gait speeds. Note the larger trunk velocity for the CIDP patient.

Fig 2. Mean 90% trunk sway measures for walking 8m with eyes open for trunk sway pitch and roll angle and angular velocity.

The height of the column represents the mean value and the vertical bar above the column the standard error of the mean (sem). Significance is shown in the figure between the means of the non-inf PNP and CIDP patients, and between the pooled mean of the patients and that of the healthy controls (HCs). The concomitant reduction of sway velocity observed in our non-inf PNP patients has been observed previously in healthy elderly controls when they reduce gait speed. Note that sway velocity for the CIDP patients is not less than that of HCs despite the markedly reduced gait speed (walking duration over 8m is significantly greater for the patients).

Fig 3. Mean trunk sway measures for standing on two legs eyes closed on a foam surface.

The layout of the figure is identical to that of Fig 2. Note that all sway measures showed highly significant increases (p≤0.006) with respect to HCs.