Walking disorders

Violation of walking is one of the most frequent and severe manifestations of neurological diseases, which often causes disability and loss of domestic independence. Despite the clinical significance and widespread prevalence, walking disorders until recently have not been the subject of a special study. Studies of recent years have significantly complicated the understanding of the phenomenology, structure and mechanisms of walking disorders. Particular attention was paid to the so-called violations of higher level walking that occur when the frontal lobes and associated subcortical structures are affected and are caused by the defeat of the regulation of walking and maintaining the balance.

Epidemiology of walking disorders

Disorders of walking are widely represented in the population, especially among the elderly. With age, their prevalence increases exponentially. Disorders of walking reveal in 15% of people over the age of 60 and 35% - over 70 years. Clinically significant violations of walking are present in about half of the people placed in nursing homes. Only 20% of people older than 85 years of walking remain normal. Among hospitalized neurological patients, walking disorders are detected in 60% of cases. Even relatively mild walking disorders are associated with an unfavorable prognosis of survival, which is explained by the increased incidence of falls, dementia, cardiovascular and cerebrovascular diseases in this population of patients, with a negative effect on survival rate increases with increasing severity of disturbances.

Physiology and pathophysiology of walking

Walking is a complex automated rhythmic act, which is provided by synergies - synchronized, time-coordinated and contractions of different muscle groups that provide targeted coordinated friendly movements. Some synergies effect a person's movement in space (locomotor synergies), others - maintain his balance (postural synergies). The straightforwardness proper to a person makes maintaining a balance when walking is particularly difficult. Each step represents an essentially controlled drop and is impossible without a short-term deviation from the equilibrium state.

Walking is a motor skill acquired in the process of individual development. Basic walking mechanisms in all people are the same, but their implementation in a particular person with certain biomechanical parameters requires a fine, improved training of tuning the various links of the motor system. Therefore, each person has his own, to a certain extent, unique manner of walking. A set of traits that characterize the originality, manner of walking in a given person or group of people, as well as the features of walking, formed under special external conditions or certain diseases, are referred to as "gait".

Walking consists of steps. Each step is an elementary locomotion cycle consisting of 2 main phases: 1 - the transfer phase, during which the foot moves in the air to the next position; 2 - the phase of the support, during which the foot contacts the surface. Normally, the length of the support phase is 60%, the transfer phase is 40% of the time of each cycle. The supporting phases of both legs are superimposed over time, and for approximately 20% of the duration of each locomotion cycle, a person rests on both legs (the double support phase).

Generation of locomotor and postural synergies and their adaptation to environmental conditions is provided by a complex, hierarchically organized system in which three basic levels can be distinguished: spinal, stem-cerebellar, higher (cortical-subcortical). The subsystems that enter into its structure solve 4 main tasks: maintaining a balance in the vertical position, initiating walking, generating rhythmic stepping movements, changing the parameters of walking depending on the person's goal and external conditions. The mechanisms of walking and maintaining equilibrium (postural control) closely interact with each other, but do not coincide with each other. Therefore, for different diseases involving certain structures of the central nervous system, they may suffer to varying degrees, which often predetermines the specificity of walking disorders and requires a special approach to rehabilitation.

• The alternate contraction of the flexors and extensors of the legs, underlying the walk, is apparently generated by a special polysynaptic mechanism implanted in animals in the lumbar and sacral segments of the spinal cord. The mechanism includes special circles of reciprocally connected intercalary neurons, some of which stimulate flexors, others - extensors (spinal walk generators). Although the existence of such structures morphologically in the human spinal cord has not yet been proven, there are indirect evidence of their existence. This, for example, is shown by observations of patients with paraplegia due to high damage to the spinal cord: when they are placed on a treadmill (with appropriate support), observe stepping movements.
• Spinal generator mechanisms are under the control of descending cortical and spinal cord pathways that promote the initiation of walking, provide fine-tuning of its parameters, especially in difficult situations, for example, when bending, overcoming obstacles, walking on uneven surfaces, etc. The initiation of walking and its speed largely depend on the activity of the mesenceptal locomotor zone, which is located in the dorsolateral part of the midbrain, and in man, apparently, corresponds to the pedunculopontin nucleus. This core contains cholinergic and glutamatergic neurons, the afferentation to which comes (through GABA -ergic projections) from the subthalamic nucleus, the pale sphere, the reticular part of the black substance, the striatum, and also the cerebellum and other stem nuclei. In turn, the neurons of the pedunculopontin nucleus send impulses to the striatum, the compact part of the black substance, the thalamus, the stem and spinal structures. It is through the pedunculopontine nucleus that the influence of the basal ganglia on walking and mediating is apparently mediated. Bilateral lesion of this zone (for example, due to a stroke) can cause slowness, difficulty in initiating walking, congealing, and postural instability.
• The cerebellum corrects the speed and amplitude of movements, coordinates the movements of the trunk and limbs, as well as various segments of one limb. Regulation of walking is provided mainly by the median structures of the cerebellum. Receiving information on spinocerebellar and corticobotocerebellar tracts, the cerebellum is able to compare the actual movements with the planned ones and, if the result deviates from the planned one, generate corrective signals. Afferentation from the middle structures of the cerebellum, following through the nuclei of the tent and then through the reticulo, vestibulo and rubrospinal tracts, controls postural synergies, trunk movements, modulates the parameters of the locomotor cycle. Through the thalamus, the cerebellum is connected with the premotor cortex and participates in the highest level of regulation of walking.
• The highest level of regulation of walking is mainly provided by the bark of the cerebral hemispheres and the subcortical structures associated with it. Its main function is the adaptation of postural and locomotor synergies to specific environmental conditions, the position of the body in space, the intentions of the individual. There are 2 main subsystems in it.
  • The first subsystem is formed by links of the main motor cortex-subcortical circle. Starting from various parts of the cortex, it consistently includes the striatum, pallidum, and thalamus neurons and returns to the extra motor cortex. The latter, interacting with other links in the circle, provides training and implementation of complex automated, enhanced locomotor and postural synergies, as well as the choice and switching of walking programs when conditions change.
  • The main component of the second subsystem of the higher level of regulation of walking is the premotor cortex, through which less automated movements are realized, which are initiated and realized under the influence of external stimuli. Through numerous cortical-cortical connections, the premolar cortex interacts with the associative zones of the parietal cortex, which, on the basis of the visual, proprioceptive, tactile, vestibular, auditory information obtained, form a diagram of the body and the surrounding space. Through the premotor cortex, the adaptation of locomotor synergies to specific surface conditions and other features of the external environment is provided. This subsystem is especially important in new unusual movements or when performing learned movements, but in an unusual context. Normal walking and maintaining balance are impossible without the feedback provided by the sensory information of the three main modalities - somatosensory, vestibular and visual. Information about the position of the body in space and the surrounding world enters all levels of walking regulation, where it undergoes processing and affects the selection and implementation of locomotor and postural synergies. The system of internal representations about the surrounding space is formed in the posterior parts of the parietal cortex, where the received sensory information is generalized in the form of spatial maps. These cards are "transferred" to the premotor cortex, striatum, the upper hills of the quadruple, where they serve as the basis for the regulation of movements.

When the sensory pathway is damaged due to the inadequate understanding of the position of the body in space and the environment, spatial and temporal coordination of movements can be violated, the choice of synergy becomes erroneous. The loss of sensory stimuli of only one modality usually does not lead to a disturbance of balance or walking, but the loss of 2 modalities significantly disturbs the equilibrium, and the violation of the 3 modalities inevitably causes gross disturbances of balance and walking, usually accompanied by frequent falls. In the elderly, the capacity for compensation is weakened, and walking disorders can be caused by the loss of sensory stimuli of only one modality or a combination of mild disorders of several modalities.

In the adaptation of locomotor and postural synergies to the current conditions, regulatory cognitive functions (such as attention, planning, control of activity) that depend on the functioning of the prefrontal cortex are important. In the spatial navigation an important role is played by the hippocampus and the para-hippocampal gyrus. The defeat of each of the levels of regulation of walking is characterized not only by the defectiveness of these or other mechanisms, but also by the specificity of compensatory strategies. Accordingly, violations of walking reflect not only the dysfunction of a particular structure, but also the inclusion of various compensatory mechanisms. As a rule, the higher the level of damage, the more limited the possibilities of compensation of a defect.

Classification of walking disorders

The difficulties in constructing a classification of walking disorders are explained by the variety of their causes, mechanisms of development and clinical manifestations. In addition, for many diseases, walking disorders have a combined nature, resulting from the interaction of several causes. In recent years, attempts have been made to classify violations of walking and balance in etiology, phenomenology, lesion localization, pathophysiological mechanism. The most successful one should recognize the attempt of JG Nutt, CD. Marsden and PD Thompson (1993) build a classification of walking disorders, based on Jackson's ideas about the levels of damage to the nervous system. They correlated disorders of walking with 3 levels of lesions of the nervous system. To disorders of the lowest level are violations of walking caused by damage to the osteoarticular apparatus and peripheral nerves, as well as a violation of sensory afferentation. Disorders of the middle level include disorders of walking caused by damage to pyramidal tracts, cerebellum, extrapyramidal structures. High-level disorders include complex, integrative disorders of motor control, which can not be explained by the defeat of the lower and middle levels. These disorders can also be described as primary because they are directly caused by a violation of the choice and initiation of locomotor and postural synergies, rather than their implementation, and do not depend on any other neurological pathology. We propose a modification of the classification of JG Nutt et al. (1993), according to which six main categories of walking disorders are identified.

• Disturbances of walking with lesions of the osteoarticular system (for example, with arthrosis, arthritis, reflex syndromes of osteochondrosis of the spine, scoliosis, rheumatic polymyalgia, etc.), which often have antalgic character.
• Disturbances of walking with dysfunction of internal organs and systems (severe respiratory and cardiac failure, obliterating lesions of the arteries of the lower limbs, orthostatic arterial hypotension, etc.).
• Disturbances of walking with dysfunction of afferent systems (sensory, vestibular, visual ataxia, multisensory insufficiency).
• Disturbances of walking caused by other motor disorders (muscle weakness, flaccid paralysis, pyramidal, cerebellar syndromes, parkinsonism, hyperkinesis).
• Walking disorders that are not associated with other neurologic disorders (integrative, or primary, walking disorders - see the corresponding section below).
• Psychogenic disorders of walking (psychogenic dysbasia in hysteria, depression and other mental disorders).

Along with this classification, reflecting the nature of walking disorders, there is a need for an exclusively phenomenological classification that would proceed from the key gait features and facilitate differential diagnosis. Various versions of the phenomenological classification of gait are proposed. For example, Jancovic (2008) identified 15 types of pathological gait: hemiparetic, paraparetic, sensory (with sensory ataxia), lagging, steppe, cautious, apratic, propulsive (or retropulsive), atactic (at cerebellar ataxia), astatic, dystonic, trochaic, antalgic, vestibulopathic, psychogenic (hysterical). Such a classification, for all its exhaustive completeness, seems unnecessarily complicated. The following types of pathological gait and their characteristics are distinguished.

• Antalgic gait is characterized by a shortening of the phase of support to the affected limb (for example, when the joints are affected and restricted mobility).
• Paralytic (hypotonic) gait is caused by weakness and decreased muscle tone (for example, a staggering gait in myopathy, stepping at polyneuropathy).
• Spastic (rigid) gait is characterized by a decrease in amplitude and slowed movements, the need for additional effort in the implementation of stepping movements, is associated with stiffness of the lower extremities due to increased muscle tone (spasticity, rigidity, dystonia).
• Hypokinetic gait is characterized by a decrease in walking speed and shortening of the step length, is most typical for parkinsonism, but its individual features are possible with depression, apathy or psychogenic disorders.
• The atactic gait is characterized by instability compensated by an increase in the footing area when walking, it is possible with violations of deep sensitivity, vestibulopathy, cerebellar pathology, decreased vision, postural synergy disorder, and also with psychogenic disorders.
• The dyskinetic gait is characterized by the presence of violent excess movements of the legs, trunk, head while walking, observing it with chorea, tics, dystonia, athetosis, ballism, myoclonia, may include arbitrary compensating movements (parakinesia) aimed at maintaining balance during walking. In a number of cases, it occurs with psychogenic disorders.
• Dysbasia is characterized by a violation of the initiation and maintenance of walking (for example, in the form of congestion or sagging walking), which is often accompanied by a defectiveness of postural synergy. This variant is observed in parkinsonism or frontal dysbasia (for example, in normotensive hydrocephalus, discirculatory encephalopathy or neurodegenerative diseases).
• Mixed gait includes features of 2 or more of these gait options.

Symptoms of walking disorders

Disturbance of walking in motor disorders

Disturbances of walking can accompany motor disorders that occur in diseases of muscles, peripheral nerves, spinal roots, pyramidal tracts, cerebellum, basal ganglia. Immediate causes of walking disorders may be muscle weakness (for example, in myopathies), flaccid paralysis (with polyneuropathies, radiculopathies, spinal cord injuries), rigidity due to pathological activity of peripheral motor neurons (with non-myomotonia, rigid body syndrome, etc.), pyramidal syndrome (spastic paralyzes), cerebellar ataxia, hypokinesia and rigidity (for parkinsonism), extrapyramidal hyperkinesis.

Diagnosis of walking disorders

Diagnosis is carried out in 2 stages. At the stage of syndromic diagnostics, the features of walking disorders and clinical signs accompanying the patient are identified and analyzed, which make it possible to draw a conclusion about the leading neurological syndrome. Later, analyzing the data of additional methods of research during the disease, conduct nosological diagnosis. The motor and sensory disturbances inherent in this or that disease of the nervous system and attempts at their compensation often form a specific gait, which is a kind of visiting card of the disease, which makes it possible to diagnose at a distance. The ability to diagnose a patient's gait is one of the most important skills of a neurologist.

Treatment of walking disorders

In the treatment of walking disorders, measures aimed at treating the underlying disease are crucial. It is important to identify and correct all additional factors that can affect walking, including orthopedic disorders, chronic pain syndromes, affective disorders. It is necessary to limit the intake of medications that can worsen walking (for example, sedatives).

Important is therapeutic gymnastics, aimed at training the skills of initiating walking, turning, maintaining balance, etc. Recognition of the main defect allows to develop a way of its compensation by connecting the stored systems. For example, you can recommend a set of special exercises of Chinese gymnastics "tai chi", developing postural stability. With multisensory insufficiency, correction of visual and auditory function, training of the vestibular apparatus, and also improvement of illumination, including at night, are effective.