Syndromes of Impaired Adaptation and Deployment of Strategies

The individual must be able to adapt synergies to the environment and situation. Much of this process occurs at a subconscious level and operates through the frontal lobe and possibly the basal ganglia. In addition, some adaptation takes place at a conscious level and is dependent on attention, learning, and insight, functions that are associated with frontal lobe function. A normal person's gait changes appropriately depending on whether the surface is flat, rough and uneven, or slippery (such as ice) and on the kind of footwear being worn (shoes, thongs, skis, stilts). Likewise, postural synergies are adapted to the situation. The postural response to a perturbation felt when standing at the end of a low diving board depends on whether the pool is filled with water and how the person is attired. Thus, equilibrium and gait are adapted to the situation through awareness of the body and the environment as well as through the use of insight, judgment, and past experience.

The cortex is not necessary for ordinary walking in laboratory animals such as cats. It is necessary for skilled walking, for example, when the cat must place its feet precisely such as when walking on the rungs of a horizontal ladder. Similarly, in humans, the frontal motor areas are presumed to be involved in precise locomotion such as walking on uneven surfaces, avoiding obstacles on the ground, and dancing.

The cautious gait, often inappropriately referred to as a senile gait, is characterized by slower, shorter steps and en bloc turns. It is not a pathological gait pattern but is a more conservative balance and gait pattern, the proper response to perceived postural insecurity in the anterior-posterior direction. A normal person assumes a cautious gait pattern on an icy surface. Older individuals assume a cautious gait pattern when they perceive that their balance or their ability to regain their balance is impaired. Widening of the base of support is an appropriate response to uncertainty about when and where the feet will make contact with the support surface and the risk of falls laterally. Just as a normal person widens the base of support on a pitching ship deck, an older individual with a cerebellar, vestibular, or somatosensory disorder widens his or her base. [20]

Dementia is not associated with a particular gait pattern, but many epidemiological studies of falls in the elderly identify dementia as one risk factor for falls. y , y Some falls appear to be due to poor insight; the patient attempts

do things that are not reasonable for his or her physical capabilities and environmental situation. Demented patients do not attend to their environment. It is probable that if dementia is combined with any problems with balance and gait, the chances of falls are markedly increased because the patient will be unable to adapt to the disabilities. In conclusion, demented patients may have normal balance synergies but cannot use them effectively because of their impaired attention and insight and an inability to profit from experience. The converse is also true. Some patients with severely compromised balance and gait synergies never fall because of their insight and carefulness.

Although balance and gait are thought of as "sub-conscious" functions, it has been demonstrated that attentional demands are needed to maintain balance and locomotion. As the difficulty of balancing or walking increases, as is common in the elderly, more attention is required. y , y Attentional demands are increased by using a walker.y Thus, inattention or distraction may impede balance and walking. The increased risk of falling associated with psychotropic drug use y may be related to the drug's effects on attention and not solely to alterations in sensory-motor function. Patients with unexplained falls may be encephalopathic from medical illnesses as well as drugs. y

The post-fall syndrome consists of a sudden inability to walk without the support of objects or the assistance of another person; it occurs after a fall, and there is no evidence of a neurological or orthopedic abnormality that explains the inability to walk. y , [40] With assistance, many of these patients can learn to walk normally. This inability to walk appears to be due to excessive fear-a perceived insecurity of balance that does not match the person's physical capacity. It might be termed an overcautious gait.

Psychogenic gait disorders can take many forms including hemiparetic and paraparetic disorders, ataxic disorders, trembling, buckling of knees, and dystonic abnormalities. Features that suggest psychogenic gait disorders include (1) variability in gait from time to time, particularly with suggestion or distraction; (2) excessive slowness and hesitation in walking; (3) tandem walking with much arm waving and swing foot wavering combined with prolonged periods of balancing on the stance foot; (4) bizarre gait patterns with no explanatory neurological findings; and (5) other historical and neurological signs suggesting a psychogenic disorder.y Neurological disorders that are sometimes improperly labeled as psychogenic are (1) dystonia, because the postures may be strange and may be present only during certain specific tasks (e.g., during walking but not running); (2) thalamic astasia, because of the striking evidence of disequilibrium combined with a lack of other neurological signs; and (3) frontal gait disorders, because of balance and gait dysfunction without other neurological signs in the presence of personality changes.

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