الفهرس 
Normal GaitOnly 14 pages are availabe for public view
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Abstract
T
he present review was carried out to evaluate the relationship between gait and changes in cognitive functions in correlation with aging and in patients with different neurologic disorders; also it has emphasized the importance of management approaches in helping patients with gait disorders to enjoy better quality of life.
Understanding the basic principles of normal gait provides a foundation for understanding pathological and compensatory gait deficits. The normal gait cycle, defined as the period between successive points at which the heel of the same foot strikes the ground.
The normal gait seldom attracts attention, but it should be observed with care if slight deviations from normal are to be appreciated. The body is erect, the head is straight, and the arms hang loosely and gracefully at the sides, each moving rhythmically forward with the opposite leg. The feet are slightly everted, the steps are approximately equal, and the internal malleoli almost touch as each foot passes the other. The medial edges of the heels, as they strike the ground with each step, form a straight line. As each leg moves forward, there is coordinated flexion of the hip and knee, dorsiflexion of the foot, and a barely perceptible elevation of the hip, so that the foot clears the ground. Also, with each step, the thorax advances slightly on the side opposite the swinging lower limb.
The entire nervous system is involved in balance and gait. Balance and gait require intact brain, spinal cord, and sensory systems. Walking messages are initiated by the motor and premotor cortex and modified by the subcortical nuclei, brainstem, and cerebellum. These all activate the spine’s central pattern generator, which coordinates arm and leg movements into rhythmic gait. Proprioceptive, visual, and vestibular inputs reach the spinal central pattern generator and affect its output. Frontal lobe systems involved in balance and gait include primary motor cortex, supplementary motor area, and prefrontal cortex. The pedunculo-pontine nucleus (PPN) is a possible brainstem center of locomotion in humans. The PPN consists of cholinergic neurons that receive inputs from prefrontal motor cortex and subthalamic regions. It has dense GABAergic afferent projections from the medial globus pallidus PPN axons project to pontomedullar motor reticular nuclei, which, in turn, provide bilateral outputs to the spinal cord. selective lesions of PPN neurons in experiments produced contralateral akinesia and bradykinesia resembling Parkinsonism with related gait disturbances.
The cerebellum is also involved in the generation of rhythmic locomotor activity through its rubrospinal, pontomedullary, reticulo-spinal, olivary, and vestibulo-spinal centers. The cerebellar vermis was shown to be activated during gait, both in normal volunteers and in parkinsonian patients.
Gait dysfunction in older people is an important public health issue. Hip fracture and other fall-related injuries often necessitate admission to nursing homes and result in a large contribution to health care expenditure. Gait disorders can also be a major risk factor for falls and are often a sign of specific underlying diseases such as normal pressure hydrocephalus, sensory disorders, myelopathy, Parkinson syndromes, and cerebellar diseases. Other contributors to gait disorders include metabolic disorders, tumors of the central nervous system (CNS), subdural hematoma, hyperthyroidism, depression, and deficiency of vitamin B12 and folate.
The gait changes with advancing age. A typical constellation includes gait slowing, shortening of the stride, and widening of the base. This results in the appearance of a guarded gait, that is, the gait of someone about to slip and fall.
Gait disturbances are among the most important motor problems associated with Parkinson’s disease (PD). They are the presenting symptom in 12–18% of the cases and will affect all patients as the disease progress .Gait disturbances can lead to falls, insecurity, fear, and loss of mobilization and independence, and institutionalization.
Parkinsonian gait is characterized by a paucity of movement of the facial, trunk, and upper and lower limb muscles, which results in a gait that is slow and shuffling with short rapid steps described as festinating. The trunk is flexed forward and the person may have difficulties with stops and turns, appearing to chase after his or her center of gravity. Joint motion is reduced due to rigidity, and there is usually little or no arm swing to help in balancing the individual. The gait in PD reflects a combination of akinesia (difficulty in initiating movement), impairment of postural reflexes, dystonia (relatively fixed abnormal postures), rigidity, and tremor.
In PSP postural instability and recurrent falls are important features that occur early in the course of the disease, often within the first year of onset of first symptoms or even as the initial symptom.
Multiple system atrophy MSA is characterized clinically by a variable combination of autonomic failure, Parkinsonism, cerebellar ataxia and pyramidal signs. The cerebellar features may predominate in some patients (MSA-C phenotype), whereas in others the parkinsonian features predominate (MSA-P phenotype). For both phenotypes, gait and balance disorders are important features, even early in the course of the disease.
Huntington’s disease is an autosomal dominant disorder characterized by chorea, behavioral changes, and frontostriatal cognitive impairment, culminating in dementia. Recent studies underscore the important contribution of bradykinesia to the movement abnormalities in this disorder. Gait has a rather unique presentation, with a mixture of chorea, ataxia and Parkinsonism.
Normal-pressure hydrocephalus NPH arises in adulthood and is characterized by a typical combination of clinical and radiological findings. The mean basal intracranial pressure is normal or mildly elevated. The typical signs of the disease are gait impairment, urinary incontinence, and dementia. The gait disorder has a frontal character with marked slowing and small shuffling steps, regular freezing, and an increased stance width, but usually with largely preserved arm movements.
Frontotemporal dementia (FTD) is the second most common type of presenile dementia and the forth most common type of senile dementia, but probably the most costly due to its florid symptom characteristics. Clinically, it often presents with changes of personality, restlessness, disinhibition, and impulsiveness and the clinical features can be complicated by neurological signs, such as motor neuron signs, Parkinsonism, and gait disturbances.
Cognition: Is what enables humans to function in everyday life: personal, social, and occupational. The ability to attend to things in a selective and focused way, to concentrate over a period of time, to learn new information and skills, to plan, to determine strategies for actions and to execute them, to comprehend language and to use verbal skills for communication and self-expression, and to retain information and manipulate it to solve complex problems are examples of mental processes that are referred to as cognitive function.
There are considerable similarities in the brain systems underlying many cognitive skills. When neurons are active they change their own local blood supply. This change can be sensed from outside the organism either by injection of a small amount of radionuclide as in positron emission topography (PET) or by sensing the magnetic signal provided by changes in hemoglobin content as is done in functional magnetic resonance (fMRI). Both of these methods have now been widely used to image discrete areas of increased neural activity during cognitive tasks. One nearly universal finding from imaging studies is that any given task activates a network of areas, including both frontal and posterior cortical and subcortical areas.
Executive function EF refers to a set of higher order cognitive processes that control, integrate, organize and maintain other cognitive abilities. EF can be divided into a number of distinct subdomains. Task planning, problem solving, sensory integration, judgment and reasoning are EF components that are intuitively related to safe navigation and mobility in complex everyday environments. EF also includes the ability to manipulate attention. EF may decline with aging and is further reduced in elderly fallers. The association between EF and gait became tighter during DT, when there was greater reliance on attentional resources. So Dual tasking DT paradigms have been widely used to investigate the effects of cognitive abilities on balance, gait and fall risk. Numerous studies have shown that DT effects are larger among elderly fallers and patients with neurological disease, such as stroke, AD or PD, compared with healthy older adults.
In MS the most common cognitive dysfunctions are those involving attention, memory, speed of information processing, visiospatial perception and learning, these dysfunction are closely related to the number and location of the CNS lesions. MS patients with problems in cognitive performance have increased odds of becoming unemployed. Importantly, cognitive symptoms in early MS are predictive of disability several years later.
In MCI cognitive deficits may be apparent across unitary or multiple domains though the person continues to maintain a high level of functional independence ; Whilst this diagnostic group is at increased risk for conversion to dementia, a substantial number of individuals remain stable or even return to normal levels of functioning with time .
Dementia is characterized by an acquired persistent impairment in at least three of the following domains of function: language, memory, visuospatial skills, executive abilities, and emotion. Dementia is a syndrome that can be produced by a wide variety of disorders; it may be reversible or irreversible. It is distinguished from mental retardation by its acquired nature and by the requirement that the patient’s function has declined from a previously more competent level.
In AD the earliest changes usually include impaired memory and a change in personality characterized by indifference. Examination at this stage typically will reveal subtle alterations in language and visuospatial abilities. As the disease progresses, memory changes become more pronounced and include both learning of new information and remote recall. The visuospatial disability worsens; the patients become disoriented easily and cannot copy or draw accurately. Language abnormalities begin with anomia and then progress to a transcortical type of aphasia with fluent verbal output, impaired comprehension of spoken speech, and relatively preserved repetition. Abstraction, calculation, and executive functions are also compromised in this stage of the illness. Motor, somatosensory, and visual function remain intact.In the final phases of the disease, essentially no memory function can be demonstrated, and language is reduced to echolalia, palilalia, and incoherent verbalization. The patient loses the ability to walk, and incontinence occurs.
Vascular dementia (VAD) accounts for between 10% and 30% of dementia in elderly persons. The clinical features include the presence of dementia, evidence of cerebrovascular disease, and a compelling association between these two characteristics .VAD may be produced by several types of cerebrovascular pathology, and several VAD syndromes are recognized.
Cognitive dysfunction is a nonmotor feature of Parkinson’s disease (PD) that contributes significantly to disability, caregiver strain, and diminished quality of life over the course of the disease. While there is not a “signature” deficit that characterizes cognitive dysfunction in PD, common features include executive dysfunction, visuospatial dysfunction, and short-termmemory deficits. Even in the earliest stages of PD, cognitive decline, and executive dysfunction in particular, is present in up to a third of patients.
Several prospective studies have reported that subjects with ‘neurologic’ gait abnormalities had an increased risk of developing dementia and cognitive decline, with gait alterations predicting the development of dementia 6 to 10 years later. These prospective studies support the notion that gait and cognitive function are connected, perhaps because they share common neural networks and/or because gait utilizes, and hence relies on, certain aspects of cognitive function. Furthermore, it has been suggested that gait changes may act as a biomarker for the future development of full-blown cognitive decline.
Gait and balance disorders are suggested to better predict imminent falls than risk factors in other domains such as impaired vision and medication. Therefore, the objective quantification of gait and balance disorders to detect persons who have high risk of falls is of utmost importance, especially in geriatric patients with cognitive decline who have a high tendency to fall. This interference of a cognitive task with gait has been demonstrated in healthy older adults, as well as in subjects with cognitive dysfunction, such as Alzheimer’s disease (AD), vascular dementia, mixed dementia and Parkinson’s disease.
Basal ganglia and their connection with cortical regions through the cortico-subcortical loops play a central role in both movement initiation and cognitive aspects, such as executive functioning. Basal ganglia activity during working memory tasks is reported in healthy control subjects, and the temporal dynamics of regional basal ganglia participation have been mapped for different phases of a working memory task .Significant increases in activation have been observed in the caudate nucleus, particularly when tasks emphasize the manipulation of information within working memory. These findings very clearly indicate that the basal ganglia comprise an essential nodule within the brain’s higher-order executive function system. Working memory requires interacting networks that include cortical and subcortical regions. The basal ganglia are involved in making perceptual discriminations and judgments and the basal ganglia are involved in procedural and instrumental learning. The basal ganglia support the acquisition of both cognitive and motor procedures. The basal ganglia appear to assist in the control of sequential or serial-order motor and cognitive learning through their unique looped connections with frontal cortices. The function of the basal ganglia appears to be to ‘‘chunk’’ together units of behavior or thought. The basal ganglia facilitate or promote the automated building-up of behavioral and cognitive units that need to be implemented in a particular temporal or sequential order.
The cerebellar functions included the control of attention and other cognitive functions, emotions and mood, and social behavior, which were all thought to represent cortical functions. The importance of this new view of cerebellar physiology has been confirmed by the frequency of neuropsychiatric disorders in individuals with cerebellar abnormalities. The cerebellar cognitive affective syndrome is a descriptive diagnostic term that can be applied to a group of cognitive, emotional, and behavioral symptoms that occur in patients with involvement of the cerebellum.
MPH significantly improved gait measures and EF (e.g., Go–No Go accuracy), but did not affect memory or finger-tapping performance. These improvements were not observed after treatment with the placebo. While alternative mechanisms may have caused the observed changes in motor function in response to the drug, one possibility is that MPH enhanced attention and this, in turn, improved gait.
In response to amantadine, several measures of gait quality improved (e.g., single support time and variability). These findings suggest that amantadine may enhance gait steadiness in patients with a frontal gait disorder. AChE inhibitors can improve gait quality and stability, and thereby reduce fall risk. AChE inhibitors are widely used to treat cognitive impairment among patients with Alzheimer’s dementia. Several studies have assessed the effects of AChE inhibitors on gait and fall risk. Those with AD who were taking donepezil improved their gait after 1 month under both single and DT walking conditions. Patients treated with galantamine had better cognitive scores compared with the control group. In addition, significant improvements in gait, freezing of gait and falls (as derived from the Unified Parkinson’s Disease Rating Scale scores) were seen in the galantamine treatment.
Vitamin D acts as mediator of fall risk because it modifies muscle strength, power and bone quality. However, several investigations have shown that vitamin D may also ameliorate fall risk by way of its effect on cognitive function.
There is good evidence that cognitive training interventions can improve cognitive function in older adults. After 5 years, training gains persisted and reasoning training resulted in less functional decline in self-reported independent instrumental activities of daily living. Cognitive training program that is designed to improve EF and attention may enhance both usual and DT walking.