Recovery of function, when the vestibular system is affected, can be enhanced by choosing the best exercise for sensory re-integration to stop the dizziness and re-establish normal balance. The progression of the exercise should correlate to the type and degree of the impairment.
The brain uses three sensory systems to determine the difference between the movement of the body and the movement around the body. The vestibular system determines the position and the movement of the head in relationship to gravity. The visual system identifies visual stability versus visual flow and works best for maintaining balance when the environment is constant. The somatosensory, or musculoskeletal systems use the angle of the body in relation to the surface, or to other parts of the body to establish the position and posture of the body. The brain must constantly compare this information and adjust to changes in the environment. For example, it is necessary to use vestibular input to determine the angle of a sloped surface when standing or walking on an incline if visual input is unavailable or disturbed. The vestibular and balance exercises in PhysioTools provide tools to facilitate adaptation of the three systems to manage dizziness and improve balance in a variety of situations and environments.
When the vestibular system is impaired the immediate result is dizziness. The primary adaptation process for vestibular disorders begins as the brain uses stable visual cues to determine the position of the head. The brain will compare information from the vestibular system and the visual system at the same time. Knowledge that the head is stable when the eyes are open is usually achieved naturally within 3-5 days as. However, the vestibular system must also adapt to the information provided by the somatosensory system and this may require additional input. Adaptation to a stable reference to the surface when the body is still but the eyes are closed is a second critical component of the adaptation process. Sensation of motion at rest can be identified when a person is sitting with good support with eyes closed. If this position creates a sensation of spinning, it is likely that the vestibular system has adapted only to visual cues and the person cannot determine that the head is stable without vision. The correct sensation of stillness can be increased by using weights on shoulders. This intensifies the somatosensory reference through the spine and should decrease the sense of spinning. Sequence activity, such as counting backwards or choosing words according to the alphabet can be used to enhance this exercise. As the system adapts, the spinning will stop and the patient can move onto the next activity.
When the sense of movement is described as light-headedness, and is increased by weights, it is likely that the somatosensory input is inaccurate. Lightheaded sensation can be seen in individuals with previous injury to the spine or with peripheral neuropathies. Further evaluation of the musculoskeletal system is indicated and exercises using a firm stable surface are appropriate.
The Vestibular ocular reflex (VOR) functions so that the eyes will automatically move at the same speed in the opposite direction that the head moves. The VOR allows the visual field to remain in focus and steady, described as gaze stability. If movement of the head results in a blurred vision, the gaze stability exercises are indicated. When performing these exercises, it is important that the target is always in clear focus and that the speed of the head movement gradually increases as the system adapts. Movement at 2Hz is considered normal; athletes should be able to move their heads at 3Hz.
Sometimes somatosensory disturbance in the neck might be responsible for head motion provoked dizziness that remains even after the VOR is normalized. Often the individual has attempted to decelerate the head by tensing/contracting the muscles in the neck during movement to avoid dizziness. This may change the way the brain is using the somatosensory input when the body is moving. One way to evaluate this is to hold the head steady while rotating the body in a chair. If this causes dizziness it may be coming from the neck. An effective exercise is to look directly into a mirror to hold the head steady as the body rotates in a swivel chair. Head turns with your eyes closed, when the body has reference to a stable surface, can also be effective to decrease this dizziness.
Dizziness due to poor adaptation of one side of the vestibular system to the other is common. Simply spinning in a chair with the eyes closed can be effective exercise. During the spin, the sensors of the neck do not contribute much to head position reference. Somatosensation will assist the vestibular system to match the head-still position when the chair stops. It is normal to feel continued spinning for 7-15 seconds after the head stops while eyes remain closed, however a poorly adapted system can take more than a minute. The chair spin then becomes the best exercise to perform at home. Typically this is done with three spins at a time and repeated three times in either direction.
The most important role of vestibular information for postural control relates to orientation of the head and trunk in space with respect to gravitational forces. Orientation to gravity is most critical when balancing on unstable surfaces without visual reference. The vestibular system provides a top-down reference for the head and trunk stability in line with gravity, while the leg segment is coordinated to maintain surface reference. Vestibular inputs are used in order to recognize the changes in angle of the support surface. Vestibular inputs are critical to determine whether the body is swaying or if the surface is perturbed. Exercises done on foam or on a small base of support facilitates the use of vestibular inputs.
When adaptation of the impaired system fails, the brain becomes over reliant on the other two functioning systems in an attempt to control symptoms and stay stable. This is commonly observed when the individual does not receive therapy, or when the therapy has not addressed the components correctly.
Once gaze stability has been established, it is important to determine the degree of visual dependence for balance. Exercises should be progressed to be performed with the eyes closed. This often makes the individual feel dizzy again, even when standing on a firm/stable surface. This phenomenon should not be perceived as a regression of the condition, but as a progression of the vestibular challenge. The patient should continue until the symptoms subside.
Somatosensory or surface dependence can interfere with the use of vestibular cues. The individual will lock the ankles at the 90 degree angle which would typically indicate that the head is vertical to the lower leg. However, when the surface is uneven, inclined or compliant, maintaining that angle will cause the head to fall in the direction of the angle, and balance is lost. Using the hands and arms to touch a surface to determine head position is common for the aging individual and in those with vestibular deficits. When this becomes a habit, the brain seeks the surface for reference, and will bypass the activation of the vestibular system. Use of the hands for balance is discouraged in balance exercise, the use of a corner will provide support from a fall. The need to hold onto something during an exercise indicates that the exercise is too difficult and should be introduced later.
Vestibular dysfunction can result in abnormal co-contraction of the neck muscles. The head stays aligned with the body during balance tasks, so when the body leans to the side the head follows as the co-contraction of the neck muscles prevents the head righting. This is most evident when the surface area is small or uneven. Instructions during exercise on a narrow surface should include keeping the head vertical, and the muscles of the neck relaxed.
Visual Motion Hypersensitivity
If the visual dependency has become severe, it is common to develop visual motion hypersensitivity. Physiologic diplopia is the double vision that is perceived as the eyes converge. It is normal that when we move our heads, the objects in our peripheral field of view will move in the opposite direction. Likewise, when the head is steady and we are following a moving target with our central vision (pursuits), the periphery of our visual field appears to move. This can create a sense of dizziness and cause instability during movement when there is an over-dependence on vision to determine head position. Likewise, the normal optokinetic flow that makes stable objects appear as moving while we are walking past them, can cause dizziness. In this case the vestibular system is not able to independently determine the movement of self. When walking past vertical targets such as cans or boxes in a grocery or hardware store, the individual may become dizzy and feel the need to stop moving. Airports, riding in the back of a car, going to the theater can cause distress for those who have visual motion sensitivity leading in avoidance.
The exercises that work best for visual motion hypersensitivity begin with looking between beads on a string (Brock string) held in front of the face. Normal diplopia of convergence will make the string appear double in front of and behind the bead in focus. Often the ability to converge the eyes is diminished in an attempt to avoid the apparent movement of the periphery during a task. Visual pursuits of a moving object may need to be started with the target moving only a small distance back and forth, and can be progressed to a figure eight or infinity sign (to get diagonal movement of the visual target). Keeping the eyes following the target of a ball thrown from one hand to the other can be started in standing and progressed to higher level of activity like exercises performed on a foam or walking.
Lack of confidence in walking is common when the vestibular system is disrupted, and is often seen in the aging population. Loss of head righting is apparent when the surface changes or when attempting to turn quickly. Visual dependence causes imbalance when the movement of the head disrupts visual stability. When the person exhibits somatosensory or surface dependence, the foot lands flat and with unusual force. To maintain normal stride with a proper heel strike, the vestibular system must be engaged. The walking exercises for dizziness and imbalance include head turns, narrow base and visual challenges.
Head Position Dizziness (Benign Paroxysmal Positional Vertigo)
Head position changes, in reference to gravity, can cause dizziness as a function of the vestibular system condition under certain circumstances. The most common form of head position dizziness in adults is benign positional vertigo or BPPV. In this condition, debris (otoconia) from the utricle moves into the semi-circular canal and there is suddenly mass in a system that is designed to calculate only fluid pressure changes in response to head movement. The added mass causes excessive deflection of the hair cells in the cupula when the head is moved into a gravity dependent position. The otoconia move in the direction of gravity through the endolymph causing a pull on the cupula and increased firing of the hair cells as if the head was moving quickly in that direction. The brain activates the VOR in response to the message that the head is moving quickly, and there is rapid eye movement or nystagmus. The nature of this nystagmus reflects the canal in which the debris is floating. As soon as the otoconia comes to rest, the pressure on the hair cell is gone, and the nystagmus subsides. This takes about 20 seconds. There is no nystagmus until the head is moved into another gravity dependent position causing the otoconia to roll through the canal. Safe and effective exercises can be done at home to recover from head position dizziness after the appropriate semicircular canal has been identified.
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