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Vestibular Rehab for Nondizzy Patients: Summary
Saccadic Eye Movements Very fast changes in eye position, moving quickly from one target to another: • Can be used in conjunction with VOR cancellation • Does not involve the vestibular system and is instead a reflex arc between the cerebellum, eyes, and midbrain • Allows the cerebellum to turn off VOR, estimate where the new target is located, and jump the visual field quickly and accurately • Helps to differentiate between peripheral vestibular issues and a central issue Vestibulospinal Reflex Main job of vestibular system: • Cerebellum coordinates inputs from vestibular, visual, and spinal somatosensory systems to determine the body’s position in space as well as its movements in space • Cerebellum uses postural stabilizers and movers to maintain upright position (such as when slipping in mud) Cervicospinal Reflex Same as the vestibulospinal reflex but focused on head position: • Neck tension/spasms, especially after injury (whiplash), will disrupt the accuracy of the neck proprioceptors and give false info to the cerebellum • Not typically the primary cause of imbalance/ dizziness but can contribute to symptoms and delay recovery VESTIBULAR PRESENTATION IN PATIENTS Common (Nonvertigo) Diagnoses • Abnormality of gait • Deconditioning: Sedentary lifestyle (due to injury, aging, etc.) leads to deconditioning of the vestibular system • Cerebral Vascular Accident (CVA): Vestibular deficit (hypofunction) may be due to the stroke, a secondary issue from before the stroke, or deconditioning after stroke; decline in vestibular acuity is most common in brainstem and cerebellar strokes: ○ Can lead to vertigo, BPPV, poor sense of body position, under/overcorrection of movement, and poor tolerance to activity ○ Primary issue with a CVA is central vestibular dysfunction, characterized by movement discoordination in trunk and extremities; nothing is particularly wrong with the peripheral system
INTRODUCTION
Balance comes from three main sensory systems: Visual, vestibular, and somatosensory. These systems evaluate the environment and movements in space to allow the body to make constant corrections to keep in the desired position. LEARNING TIP! The vestibular system’s main job is to tell the brain the head’s position and how it is moving, as well as to smooth out optical illusions and help judge or “fact check” if there is a discrepancy between information from the three systems. Often, the vestibular system and its ability to coordinate with the visual and postural reflex systems are neglected in rehab. For the elderly, falls are a significant danger and risk factor for impairment of functional independence as well as general health and safety. Contributing to this increased fall risk is the decline in vestibular acuity and usage. After age 40, there is a decline in vestibular function, reaching a 40% loss by age 75 . This decline in vestibular function makes a person significantly more likely (51%) to fall and injure themselves (Herdman, 2014; Liston et al., 2014). When a clinician addresses functional balance ability and fall prevention interventions, the vestibular system must be addressed directly. VESTIBULAR ANATOMY AND REFLEXES
Vestibular Ocular Reflex (VOR) Enables clear vision during motion:
• Allows the cerebellum to coordinate eye movements to allow the visual focal point to stay on target with head movement • Can occur during both small movements (e.g., breathing) and large movements (e.g., running) Smooth Pursuits The opposite of VOR: • Allow a person’s head to remain still while visually tracking a moving target • Cerebellum monitors neck position and eye movements to maintain a smooth, linear motion that keeps up with the speed of the target VOR Cancellation Both head and eyes are following a moving target: • Cerebellum cancels the VOR and allows the eyes and neck to track the target together *All three reflexes use the same central pathways coordinated by the cerebellum.*
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