Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum. Ataxia can be limited to one side of the body, which is referred to as hemiataxia. Several possible causes exist for these patterns of neurological dysfunction. Dystaxia is a mild degree of ataxia. Friedreich's ataxia has gait abnormality as the most commonly presented symptom. The word is from Greek α- [a negative prefix] + -τάξις [order] = "lack of order".
Hemiparesis, or unilateral paresis, is weakness of one entire side of the body. Hemiplegia is, in its most severe form, complete paralysis of half of the body. Hemiparesis and hemiplegia can be caused by different medical conditions, including congenital causes, trauma, tumors, or stroke.
A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness, or wooziness, or having a sensation of movement, spinning, or floating. Balance is the result of several body systems working together: the visual system (eyes), vestibular system (ears) and proprioception. Degeneration or loss of function in any of these systems can lead to balance deficits.
Acrophobia is an extreme or irrational fear or phobia of heights, especially when one is not particularly high up. It belongs to a category of specific phobias, called space and motion discomfort, that share both similar causes and options for treatment.
The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear in most mammals.
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain, a deficit in attention and awareness towards the side of space opposite brain damage is observed. It is defined by the inability of a person to process and perceive stimuli towards the contralesional side of the body or environment. Hemispatial neglect is very commonly contralateral to the damaged hemisphere, but instances of ipsilesional neglect have been reported.
Sensory processing is the process that organizes sensation from one's own body and the environment, thus making it possible to use the body effectively within the environment. Specifically, it deals with how the brain processes multiple sensory modality inputs, such as proprioception, vision, auditory system, tactile, olfactory, vestibular system, interoception, and taste into usable functional outputs.
Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties walking. It is typically worse when the head is moved. Vertigo is the most common type of dizziness.
Romberg's test, Romberg's sign, or the Romberg maneuver is a test used in an exam of neurological function for balance, and also as a test for driving under the influence of an intoxicant. The exam is based on the premise that a person requires at least two of the three following senses to maintain balance while standing: proprioception ; vestibular function ; and vision.
The vestibular nerve is one of the two branches of the vestibulocochlear nerve. In humans the vestibular nerve transmits sensory information transmitted by vestibular hair cells located in the two otolith organs and the three semicircular canals via the vestibular ganglion of Scarpa. Information from the otolith organs reflects gravity and linear accelerations of the head. Information from the semicircular canals reflects rotational movement of the head. Both are necessary for the sensation of body position and gaze stability in relation to a moving environment.
The vestibulospinal tract is a neural tract in the central nervous system. Specifically, it is a component of the extrapyramidal system and is classified as a component of the medial pathway. Like other descending motor pathways, the vestibulospinal fibers of the tract relay information from nuclei to motor neurons. The vestibular nuclei receive information through the vestibulocochlear nerve about changes in the orientation of the head. The nuclei relay motor commands through the vestibulospinal tract. The function of these motor commands is to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head.
Somatosensory amplification (SSA) is a tendency to perceive normal somatic and visceral sensations as being relatively intense, disturbing and noxious. It is a common feature of hypochondriasis and is commonly found with fibromyalgia, major depressive disorder, some anxiety disorders, Asperger syndrome, and alexithymia. One common clinical measure of SSA is the Somatosensory Amplification Scale (SSAS).
Balance in biomechanics, is an ability to maintain the line of gravity of a body within the base of support with minimal postural sway. Sway is the horizontal movement of the centre of gravity even when a person is standing still. A certain amount of sway is essential and inevitable due to small perturbations within the body or from external triggers. An increase in sway is not necessarily an indicator of dysfunctional balance so much as it is an indicator of decreased sensorimotor control.
Tactile discrimination is the ability to differentiate information through the sense of touch. The somatosensory system is the nervous system pathway that is responsible for this essential survival ability used in adaptation. There are various types of tactile discrimination. One of the most well known and most researched is two-point discrimination, the ability to differentiate between two different tactile stimuli which are relatively close together. Other types of discrimination like graphesthesia and spatial discrimination also exist but are not as extensively researched. Tactile discrimination is something that can be stronger or weaker in different people and two major conditions, chronic pain and blindness, can affect it greatly. Blindness increases tactile discrimination abilities which is extremely helpful for tasks like reading braille. In contrast, chronic pain conditions, like arthritis, decrease a person's tactile discrimination. One other major application of tactile discrimination is in new prosthetics and robotics which attempt to mimic the abilities of the human hand. In this case tactile sensors function similarly to mechanoreceptors in a human hand to differentiate tactile stimuli.
Sensory stimulation therapy (SST) is an experimental therapy that aims to use neural plasticity mechanisms to aid in the recovery of somatosensory function after stroke or cognitive ageing. Stroke and cognitive ageing are well known sources of cognitive loss, the former by neuronal death, the latter by weakening of neural connections. SST stimulates a specific sense at a specific frequency. Research suggests that this technique may reverse cognitive ageing by up to 30 years, and may selectively improve or impair two point discrimination thresholds.
The righting reflex, also known as the labyrinthine righting reflex, is a reflex that corrects the orientation of the body when it is taken out of its normal upright position. It is initiated by the vestibular system, which detects that the body is not erect and causes the head to move back into position as the rest of the body follows. The perception of head movement involves the body sensing linear acceleration or the force of gravity through the otoliths, and angular acceleration through the semicircular canals. The reflex uses a combination of visual system inputs, vestibular inputs, and somatosensory inputs to make postural adjustments when the body becomes displaced from its normal vertical position. These inputs are used to create what is called an efference copy. This means that the brain makes comparisons in the cerebellum between expected posture and perceived posture, and corrects for the difference. The reflex takes 6 or 7 weeks to perfect, but can be affected by various types of balance disorders.
The fear of falling (FOF), also referred to as basophobia, is a natural fear and is typical of most humans and mammals, in varying degrees of extremity. It differs from acrophobia, although the two fears are closely related. The fear of falling encompasses the anxieties accompanying the sensation and the possibly dangerous effects of falling, as opposed to the heights themselves. Those who have little fear of falling may be said to have a head for heights. Basophobia is sometimes associated with astasia-abasia, the fear of walking/standing erect.
The term chronic subjective dizziness (CSD) is used to describe a commonly encountered type of dizziness that is not easily categorized into one of several other types, and for which the physical examination is typically normal. Patients with CSD frequently initially suffer a sudden injury of some sort to their vestibular system, the neurologic network that preserves sense of balance. Even after this initial injury has healed, people with CSD usually describe a vague sense of unsteadiness worsened by triggers in their environment such as high places, standing on moving objects, or standing in motion-rich environments like busy streets or crowds. There is a clear indication that anxiety and other mental illnesses play a role in the dizziness symptoms that occur with CSD. However, the condition is categorized as chronic functional vestibular disorder, not as a structural or psychiatric condition.
Vestibular rehabilitation (VR), also known as vestibular rehabilitation therapy (VRT), is a specialized form of physical therapy used to treat vestibular disorders or symptoms, characterized by dizziness, vertigo, and trouble with balance, posture, and vision. These primary symptoms can result in secondary symptoms such as nausea, fatigue, and lack of concentration. All symptoms of vestibular dysfunction can significantly decrease quality of life, introducing mental-emotional issues such as anxiety and depression, and greatly impair an individual, causing them to become more sedentary. Decreased mobility results in weaker muscles, less flexible joints, and worsened stamina, as well as decreased social and occupational activity. Vestibular rehabilitation therapy can be used in conjunction with cognitive behavioral therapy in order to reduce anxiety and depression resulting from an individual's change in lifestyle.
