Differences in stabilometric correlates of pain relief after wearing postural insoles for six weeks between chronic nociceptive and neuropathic foot pain. An open-label pilot study

Impact of textured surfaces on the orthostatic balance of patients with multiple sclerosis

OBJECTIVE

To perform posturographic measurements with eyes open or closed using floor coverings with different textured surfaces to study postural control in patients with multiple sclerosis (MS).

METHODS

Static posturographic recordings were performed with eyes open and eyes closed on a forceplate with no covering (control condition) or covered by a textured mat with small pimples (height 2 mm) or large pimples (height 7 mm). Several posturographic variables were measured, focusing on displacements of the center of pressure (CoP) including the average velocity (Vav), the total length (L) of all displacements, and the surface (S) of the confidence ellipse. The recordings made with the textured mats were compared to the control condition with eyes open or closed. Then, the differences between the recordings made with large vs. small pimples on the one hand, and with eyes closed vs. open were calculated to assess the impact of pimple height or eye closure on posturographic measurements. Clinical assessment was based on the Expanded Disability Status Scale (EDSS) and its functional system (FS) subscores, the Modified Fatigue Impact Scale (MFIS), the Unipodal Stance test (UST), and the Timed Up-and-Go test (TUG).

RESULTS

Forty-six MS patients (mean EDSS score: 3.6) completed the study. Several posturographic variables, including Vav and L, deteriorated when measured on a textured mat, especially with large pimples and in eyes open condition. In contrast, no difference was found with small pimples and eyes closed, as compared to the control condition (no covering). The deleterious impact of pimple height on posturography correlated positively with the alteration of balance and gait clinically assessed by the UST and the TUG, and also with the MFIS physical and cerebral EDSS-FS subscores, and negatively with the cerebellar and brainstem subscores. On the other hand, the impact of eye closure on posturography was negatively correlated with the visual EDSS-FS subscore.

DISCUSSION

Static posturographic measurements made with different textured surfaces and visual conditions can be considered as a sensitive tool to measure "proprioceptive reserves". Actually, when cerebellar, brainstem, or visual functions are impaired, the resources of the sensory (proprioceptive) system, if preserved, can be recruited at a higher level and compensate for dysfunctions of other postural controls to maintain a satisfactory balance. In addition, this procedure of static posturographic examination can provide objective measurements correlated with clinical testing of balance and gait and could usefully complement EDSS scoring to assess disability affecting postural control and the risk of falling in MS patients.

Impact of five floor coverings on the orthostatic balance of healthy subjects

Plantar skin sensitivity contributes to the regulation of postural control and, therefore, changing the characteristics of the plantar support surface can modify this control. This study aimed at assessing the impact of five different floor coverings on the orthostatic balance in 48 healthy subjects. Static posturography was performed with eyes open or closed on a platform in a control condition (no covering) and with five different covering surfaces: foam, silicone, ethyl vinyl acetate, and two textured mats with small (height 2 mm) or large pimples (7 mm). The average velocity of center of pressure (CoP) displacement was the primary endpoint measure and ten other posturographic variables were assessed. Comfort and pain produced by the covering were also scored. In eyes open condition, the average velocity of CoP displacement was increased when subjects stood on the foam mat, the silicone mat, and especially the textured mat with large pimples. Several other posturographic variables showed significant changes with different types of floor coverings with eyes open. These changes were not correlated to the comfort or pain scores associated with the different surfaces. In contrast, no difference was observed compared to the control condition (no covering) with eyes closed. This study shows that adding smooth or textured floor covering can alter balance in eyes open condition. In eyes closed condition, although more disturbing for balance, healthy subjects achieved better postural adaptation, probably by mobilizing more of their proprioceptive resources. This posturographic examination procedure could, therefore, be used to assess "proprioceptive reserve" capacities in clinical practice.

Small fiber neuropathy

Small fiber neuropathy (SFN) is a peripheral nervous system disease due to affection of A-delta or C-fibers in a proximal, distal, or diffuse distribution. Selective SFN (without large fiber affection) manifests with pain, sensory disturbances, or autonomic dysfunction. Though uniform diagnostic criteria are unavailable, most of them request typical clinical features and reduced intra-epidermal nerve fiber density on proximal or distal skin biopsy. Little consensus has been reached about the treatment of SFN, why this narrative review aims at summarizing and discussing treatment options for SFN. Treatment of SFN can be classified as symptomatic, pathophysiologic, or causal. Prerequisites for treating SFN are an established diagnosis, knowledge about the symptoms and signs, and the etiology. Pain usually responds to oral/intravenous pain killers, antidepressants, anti-seizure drugs, or topical, transdermal specifications. Some of the autonomic disturbances respond favorably to symptomatic treatment. SFN related to Fabry disease or hATTR are accessible to pathogenesis-related therapy. Immune-mediated SFN responds to immunosuppression or immune-modulation. Several of the secondary SFNs respond to causal treatment of the underlying disorder. In conclusion, treatment of SFN relies on a multimodal concept and includes causative, pathophysiologic, and symptomatic measures. It strongly depends on the clinical presentation, diagnosis, and etiology, why it is crucial before initiation of treatment to fix the diagnosis and etiology. Due to the heterogeneous clinical presentation and multi-causality, treatment of SFN should be individualized with the goal of controlling the underlying cause, alleviating pain, and optimizing functionality.