Chapter 22: Effects of Peripheral Neuropathy on Posture and Balance

Objectives

On completion of this chapter, the student/practitioner will be able to:

• Discuss the relationship of afferent and efferent peripheral nerve contributions to normal balance and postural control.

• Discuss the functional relationship of loss of balance-related sensory pathways.

• Identify the positional and functional impact of diabetic sensory neuropathy.

• Explain the relationship between falls and neuropathy.

Key Terms

• Balance

• Postural compensation

• Postural control

Introduction

Falls resulting in significant injury are a major health issue for older adults. Instability that results in a fall is the leading cause of injury-related death and of nonfatal injury in the United States.^1–3 The probability that an adult will experience a fall increases with age and with age-related disease. It has been reported that individuals with diabetes mellitus experience subjective feelings of instability, and the risk of falling is increased by a factor of 15 in patients with diabetic neuropathy compared with healthy individuals.^4,5 The dynamic process of maintaining an upright posture is vital to the health and independent functioning of the aging population. However, the mechanisms that are necessary for the maintenance of upright posture are exactly the ones impacted by the presence of peripheral neuropathy.

Postural control is the result of a continuous integration of information from the convergence of multiple sensory receptors. Proprioceptive, vestibular, and visual signals have been most frequently identified as the primary contributors to postural control, but corrective postural responses can also be influenced by other somatosensory feedback (e.g., tactile) as well as feedforward (e.g., prediction of a slippery surface) mechanisms. Because there are so many possible pathways that could signal the beginning of a fall, one would think that even if any single input were lost, the other pathways would provide sufficient detail for the postural response to be appropriate to the task demands. However, each sensory pathway has well-defined sensitivities to environmental stimuli.

For example, imagine the cyclists in Figure 22-1. Do they rely more heavily on their motor plan for advancing beyond the other cyclists or reacting to what they see and hear the others doing? Or do they pay more attention to their muscle and joint receptors telling them how fast they are pedaling or how fatigued they are getting? With all of this continuous feedback, when do they focus on the vestibular information that may be telling them they are starting to tilt? Sensitivities of the pathways for sensory information completely overlap,^6–8 and experimental studies have been able to exclude any single input (i.e., proprioceptive,⁹ visual,¹⁰ vestibular,¹¹ or plantar cutaneous¹²) as the primary trigger for the automatic postural reactions. Instead, the specialized characteristics of ...