Gardoni Andrea [Neuroimaging Research Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy; and Vita-Salute San Raffaele University, Milan, Italy]
Sarasso Elisabetta [Neuroimaging Research Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy; and Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal Child Health, University of Genoa, Genoa, Italy]
Sorrenti Benedetta [Neurology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy; and Vita-Salute San Raffaele University, Milan, Italy]
Pietroni Luca [Vita-Salute San Raffaele University, Milan, Italy]
Bosco Luca [Neurology Unit and Neurophysiology Service, IRCCS San Raffaele Scientific Institute, Milan, Italy]
Strano Camilla Mirella Maria [Neurology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy; and Vita-Salute San Raffaele University, Milan, Italy]
Zenere Lucia [Neuroimaging Research Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy]
Falzone Yuri Matteo [Neurology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy]
Agosta Federica [Neuroimaging Research Unit, Division of Neuroscience, and Neurology Unit IRCCS San Raffaele Scientific Institute, Milan, Italy; and Vita-Salute San Raffaele University, Milan, Italy]
Previtali Stefano Carlo [Neurology Unit and Institute of Experimental Neurology and Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy] Filippi Massimo [Neuroimaging Research Unit, Division of Neuroscience; Neurology Unit; Neurorehabilitation Unit; and Neurophysiology Service, IRCCS San Raffaele Scientific Institute, Milan, Italy; and Vita-Salute San Raffaele University, Milan, Italy]
People with peripheral neuropathy present an increased risk of falls due to an impaired balance control resulting from muscular weakness and/or reduced sensation. This study aimed at investigating the impact of muscular weakness and somatosensory deficits on steady-state and dynamic balance in people with peripheral neuropathy.
Twenty patients with Charcot-Marie-Tooth (CMT), 17 patients with predominantly motor disorders (MOT) (hereditary motor neuropathy or distal myopathy), 9 patients with sensory neuropathy (SENS) and 10 healthy controls were included. Subjects underwent: lower limb muscle strength tests; tactile sensitivity and pallesthesia assessments; evaluation of tactile-pressure sensory threshold of plantar surface of the foot with Semmes-Weinstein monofilaments; measure of passive range of motion of the ankle; static and dynamic balance tests with the Balance Evaluation Systems Test (BESTest). Specific items from the BESTest were performed on a force platform to observe center of pressure (COP) displacement during the exploration of stability limits, the anticipatory postural adjustments (APA) and the maintenance of orthostatism under sensory deprivation conditions.
Assessments confirmed the presence of sensory deficit in CMT and SENS patients. CMT and MOT groups were weaker than the controls; SENS had no significant differences with healthy subjects on lower limb strength. CMT, MOT and SENS patients showed significant impairment in steady-state and dynamic balance compared with controls. No statistically significant difference was observed between CMT, SENS and MOT patients in reactive balance. SENS performed better than CMT patients in proactive balance. Stability limits were similar among the different groups, while the amplitude of APA was on average greater in patients than in controls. In static balance, patients with sensory deficits had greater COP oscillations than MOT and controls. On the other hand, the latter groups performed similarly in static oscillations. In the CMT group, increased time at the Timed-Up-and-Go test and reduced BESTest score correlated with sensory deficit, dorsal and plantar flexor weakness, and disease severity.
Somatosensory deficit and muscular weakness play different roles in postural instability in individuals with peripheral neuropathies. Isolated distal muscle recruitment deficits do not seem to affect steady-state balance, whereas sensory deficits play a pivotal role on instability in static conditions. Both strength and sensory deficits impact on the ability to maintain balance on unstable surface and on dynamic balance, with the latter being mostly dependent on the integrity of the motor system. These findings provide new insights into the systems responsible for postural instability in patients with peripheral neuropathies and justify further research on the efficacy of rehabilitative treatments focused on improving balance in patients with distal deficits, whether they are motor or sensory.
