While everyone knows about the “five senses” – sight, hearing, smell, taste, touch – little attention is paid to another of important sense, the sense of balance, unless problems develop. Many of the neuromuscular diseases affect balance.
The sense of balance informs the brain about where one’s body is in space, including what direction the body moves and points and if the body remains still or moves. The sense of balance relies on sensory input from a number of systems. Disruption in any of the following systems can affect balance and equilibrium:
--Proprioception involves the sense of where one’s body is in space. Sensory nerves in the neck, torso, feet and joints provide feedback to the brain that allows the brain to keep track of the position of the legs, arms, and torso. The body then can automatically make tiny changes in posture to help maintain balance.
--Sensors in the muscles and joints also provide information regarding which parts of the body or in motion or are still.
--Visual information provides the brain with observations regarding the body’s placement in space. In addition, the eyes observe the direction of motion.
--The inner ears (labyrinth and vastibulocochlear nerve) provide feedback regarding direction of movement, particularly of the head.
--Pressure receptors in the skin send information to the brain regarding what parts of the body are in space and which part touch the ground (when standing), a chair (when sitting), or the bed (when reclining).
--The central nervous system (the brain and spinal cord) integrates and processes the information from each of these sources to provide one with a “sense of balance.”
Problems with balance may occur in many individuals with neuromuscular disease. For example, problems with proprioception often occur in individuals with diseases such as Freidreich’s ataxia, Charcot Marie Tooth, myopathy, and spinal muscular atrophy due to loss of sensation in the joint. Sensory loss at the skin may affect the pressure receptors of a person with Charcot Marie Tooth. Visual losses and severe muscle weakness can lead to balance difficulties for those with mitochondrial myopathy. Loss of muscle strength occurring in many of the neuromuscular disease can also contribute to balance problems.
Problems with balance can also contribute to problems such as poor gait, clumsiness, and falling in children and adults. Falling can cause injury, including minor injuries such as cuts and bruises, as well as major injuries such as bone fractures and head injury. Poor balance can also lead to sensations such as disequilibrium, light-headedness, dizziness, and vertigo. Balance problems may also lead to social embarrassment.
Individuals with problems in one of the systems related to balance may rely more heavily on other systems for maintaining balance. For example, an individual with a deficit in proprioception may rely more heavily on visual input to maintain balance. Balance may then be more obviously impaired when input from that sense is not available, for example when walking in darkness.
Individuals with neuromuscular disease may benefit from consulting their physicians regarding methods for improving balance. Methods may include learning new movement habits, improving concentration and attention to movement, engaging in physical therapy and appropriate moderate exercise, making home modification, and using of assistive devices.
Even though sense of balance has often been overlooked unless problems develop, one’s sense of balance provides important sensory information that impacts quality of life. A better understanding of this important sense can help individuals to cope better with the challenges of living with neuromuscular disease.
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