Chapter 024. Gait and Balance Disorders (Part 1)

Harrisons Internal Medicine Chapter 24. Gait and Balance DisordersPrevalence, Morbidity, and MortalityGait and balance problems are common in the elderly and contribute to the risk of falls and injury. Gait disorders have been described in 15% of individuals over the age of 65. By age 80, one person in four will use a mechanical aid to assist ambulation.Among those 85 and older, the prevalence of gait abnormality approaches 40%. In epidemiologic studies, gait disorders are consistently identified as a major risk factor for falls and injury.A substantial number of older persons report insecure balance and experience falls and...
Nội dung trích xuất từ tài liệu:
Chapter 024. Gait and Balance Disorders (Part 1) Chapter 024. Gait and Balance Disorders (Part 1) Harrisons Internal Medicine > Chapter 24. Gait and Balance Disorders Prevalence, Morbidity, and Mortality Gait and balance problems are common in the elderly and contribute to therisk of falls and injury. Gait disorders have been described in 15% of individualsover the age of 65. By age 80, one person in four will use a mechanical aid toassist ambulation. Among those 85 and older, the prevalence of gait abnormality approaches40%. In epidemiologic studies, gait disorders are consistently identified as a majorrisk factor for falls and injury. A substantial number of older persons report insecure balance andexperience falls and fear of falling. Prospective studies indicate that 20–30% ofthose over age 65 fall each year, and the proportion is even higher in hospitalizedelderly and nursing home patients. Each year 8% of individuals >75 suffer aserious fall-related injury. Hip fractures often result in hospitalization and nursinghome admission. For each person who is physically disabled, there are others whosefunctional independence is constrained by anxiety and fear of falling. Nearly onein five of elderly individuals voluntarily limit their activity because of fear offalling. With loss of ambulation, there is a diminished quality of life and increasedmorbidity and mortality. Anatomy and Physiology Upright bipedal gait depends on the successful integration of posturalcontrol and locomotion. These functions are widely distributed in the centralnervous system. The biomechanics of bipedal walking are complex, and the performance iseasily compromised by injury at any level. Command and control centers in thebrainstem, cerebellum, and forebrain modify the action of spinal pattern generatorsto promote stepping. While a form of fictive locomotion can be elicited from quadrupedalanimals after spinal transection, this capacity is limited in primates. Stepgeneration in primates is dependent on locomotor centers in the pontinetegmentum, midbrain, and subthalamic region. Locomotor synergies are executedthrough the reticular formation and descending pathways in the ventromedialspinal cord. Cerebral control provides a goal and purpose for walking and is involved inavoidance of obstacles and adaptation of locomotor programs to context andterrain. Postural control requires the maintenance of the center of mass over thebase of support through the gait cycle. Unconscious postural adjustments maintainstanding balance: long latency responses are measurable in the leg muscles,beginning 110 ms after a perturbation. Forward motion of the center of mass provides propulsive force forstepping, but failure to maintain the center of mass within stability limits results infalls. The anatomic substrate for dynamic balance has not been well defined, butthe vestibular nucleus and midline cerebellum contribute to balance control inanimals. Human patients with damage to these structures have impaired balancewith standing and walking. Standing balance depends on good quality sensory information about theposition of the body center with respect to the environment, support surface, andgravitational forces. Sensory information for postural control is primarily generated by thevisual system, the vestibular system, and by proprioceptive receptors in the musclespindles and joints. A healthy redundancy of sensory afferent information isgenerally available, but loss of two of the three pathways is sufficient tocompromise standing balance. Balance disorders in older individuals sometimes result from multipleinsults in the peripheral sensory systems (e.g., visual loss, vestibular deficit,peripheral neuropathy), critically degrading the quality of afferent informationneeded for balance stability. Older patients with mental status abnormalities and dementia fromneurodegenerative diseases appear to be particularly prone to falls and injury.Frailty, muscle weakness, and deconditioning undoubtedly contribute to the risk.There is a growing literature on the use of attentional resources to managelocomotion. The ability to walk while attending to a cognitive task (dual tasking) maybe particularly compromised in older adults with a history of falls. Walking isgenerally considered to be unconscious and automatic, but older patients withdeficits in executive function may be unable to manage the attention needed fordynamic balance when distracted.