**5. Balance in patients with peripheral neuropathy**

Patients with polyneuropathy, which reduces sensation and often strength in the lower extremities, may have decreased stability while standing and when subjected to dynamic balance conditions [28, 94-97]. In patients with severe peripheral neuropathy of unknown origin, compared to healthy age and sex matched controls, visual and vestibular input cannot fully compensate for the impairment in proprioception, with progressive deterioration of balance [31].

The ability to re-weight sensory information depending on the sensory context is important for maintaining stability, when an individual moves from one sensory context to another, such as a flat walking surface to an uneven surface or a well-lit sidewalk to a dimly lit garden. Individuals with peripheral vestibular loss or somatosensory loss from neuropathy are limited in their ability to re-weight postural sensory dependence [31, 98].

In patients with peripheral neuropathy, including Charcot-Marie-Tooth disease type 1A and type 2 and diabetic neuropathy, the effects of impaired proprioceptive input in balance control under static and dynamic conditions [99] showed that, during static conditions, across all patients, instability increased as a function of the slowing of conduction velocity. In contrast, during dynamic conditions head displacement was only slightly increased, compared to healthy subjects, despite the increased delay at which the head followed displacement of the feet.

Charcot–Marie–Tooth disease is a genetically heterogeneous group of hereditary neuropa‐ thies characterized by slowly progressive weakness and atrophy, primarily in the distal leg muscles. The clinical disability has been shown to best correlate with the degree of axonal loss [100]. However, evidence suggest that functional integrity of the largest afferent fibres is not necessary for appropriate equilibrium control during quiet stance, and unsteadi‐ ness is related to additional functional alterations in smaller fibres, most likely group II spindle afferent fibres [39].

In adult patients with Charcot–Marie-Tooth type 1A, the decline in axonal function and in muscle strength may reflect, to a considerable extent, a process of normal ageing, and physical disability in adulthood may well be explained by decreased reserves and compen‐ satory mechanisms together with progression of skeletal deformations due to muscle weakness [101]. On the other hand, during static conditions, patients with Charcot-Marie-Tooth type 2 may show less postural stability than patients with Charcot-Marie-Tooth type 1A disease, but similar than the postural stability shown by diabetic patients with periph‐ eral neuropathy [99]; while in patients with diabetic peripheral neuropathy, unsteadiness relates to alterations in medium-size myelinated afferent fibres, possibly originating from spindle secondary terminations [40].

the termination and the associated movements. During stepping, it is important to evaluate at

132 Peripheral Neuropathy - A New Insight into the Mechanism, Evaluation and Management of a Complex Disorder

The analysis of gait may include measurements of joint kinematics and kinetics, other meas‐ urements include electromyography, oxygen consumption and foot pressures. Using electro‐ myography, specific muscles or muscle groups during movement can be studied. A kinematic evaluation (e.i. joint angles, stride length, walking velocity) may be performed by optoelectric methods as well as by tracking the position of the body segments using light-emitting markers. Power is a kinetic variable, to assess the rate of work performed at a given joint [93], which allows to identify when the muscle is generating or absorbing mechanical energy (concentric

Patients with polyneuropathy, which reduces sensation and often strength in the lower extremities, may have decreased stability while standing and when subjected to dynamic balance conditions [28, 94-97]. In patients with severe peripheral neuropathy of unknown origin, compared to healthy age and sex matched controls, visual and vestibular input cannot fully compensate for the impairment in proprioception, with progressive deterioration of

The ability to re-weight sensory information depending on the sensory context is important for maintaining stability, when an individual moves from one sensory context to another, such as a flat walking surface to an uneven surface or a well-lit sidewalk to a dimly lit garden. Individuals with peripheral vestibular loss or somatosensory loss from neuropathy are limited

In patients with peripheral neuropathy, including Charcot-Marie-Tooth disease type 1A and type 2 and diabetic neuropathy, the effects of impaired proprioceptive input in balance control under static and dynamic conditions [99] showed that, during static conditions, across all patients, instability increased as a function of the slowing of conduction velocity. In contrast, during dynamic conditions head displacement was only slightly increased, compared to healthy subjects, despite the increased delay at which the head followed displacement of the

Charcot–Marie–Tooth disease is a genetically heterogeneous group of hereditary neuropa‐ thies characterized by slowly progressive weakness and atrophy, primarily in the distal leg muscles. The clinical disability has been shown to best correlate with the degree of axonal loss [100]. However, evidence suggest that functional integrity of the largest afferent fibres is not necessary for appropriate equilibrium control during quiet stance, and unsteadi‐ ness is related to additional functional alterations in smaller fibres, most likely group II

In adult patients with Charcot–Marie-Tooth type 1A, the decline in axonal function and in muscle strength may reflect, to a considerable extent, a process of normal ageing, and

least the speed of walking, the rhythm and the length of each stride.

**5. Balance in patients with peripheral neuropathy**

in their ability to re-weight postural sensory dependence [31, 98].

or eccentric contraction).

balance [31].

feet.

spindle afferent fibres [39].

A frequent source of polyneuropathy is diabetes mellitus. Diabetic peripheral neuropathy is initially characterized by a reduction in somesthesic sensitivity due to the sensitive nerve damage, and with progression motor nerves are damaged. During upright stance, compared to healthy subjects, recordings of the centre of pressure in patients with diabetic neuropathty have shown larger sway [95-96, 102], as well as increased oscillation at 0.5-1 Hz [103]. However, in this group of patients, in addition to postural instability caused by neuropathy, balance deterioration may also result from the bio-mechanical impairment caused by progression of foot complications [104], as well as from the compromise of other sensory inputs such as vision [105-106]. Compared to healthy subjects, diabetic patients may have poorer balance during standing in diminished light compared to full light and no light conditions [105].

Balance and gait difficulties are the most frequently cited cause of falling in all age and gender groups [107] A fall is often defined as inadvertently coming to rest on the ground, floor or other lower level, excluding intentional change in position to rest in furniture, wall or other objects [108]. Cavanagh et al. (1992) [109] have shown that, compared to patients with diabetes but no peripheral neuropathy, patients with diabetic peripheral neuropathy are more likely to report an injury during walking or standing, which may be more frequent when walking on irregular surfaces [110].

Epidemiological surveys have established that a reduction of leg proprioception is a risk factor for falls in the elderly [111-112]. Symptoms and signs of peripheral neuropathy are frequently found during physical examination of older subjects. These clinical manifestations may be related to diabetes mellitus, alcoholism, nutritional deficiencies, autoimmune diseases, among other causes. In this group of patients, loss of plantar sensation may be an important contrib‐ utor to the dynamic balance deficits and increased risk of falls [34, 109].

Falls occur as a result of complex interactions among demographic, physical and behavioural factors. Risk factors may be intrinsic or extrinsic: intrinsic factors include demographic and biological factors, while extrinsic factors encompass environmental and behavioural factors [108]. Among other risk factors, the occurrence of falls may be significantly associated with lower extremity weakness, which can be measured by knee extension, ankle dorsiflexion, and chair stands [113], visual acuity of less than 6/12 [114], lower extremity impairments [108-109] and poly-pharmacy [115-116].

Apart from sensorymotor compromise, fear of falling may relate to restriction and avoidance of activities, which results in loss of strength especially in the lower extremities, and may also be predictive for future falls [117-119].
