________________________________________________________________________ Dizziness and Vertigo
The psychiatric perspective is important, but inadequate by fail- ing to consider recent evidence implicating vestibular dysfunc- tion, impaired multisensory integration, and sensory mismatch in depersonalization/derealization [85; 86]. Vestibular inputs provide a frame of reference within which spatial information from other senses is interpreted. Depersonalization/derealiza- tion associated with vestibular dysfunction is a consequence of a sensory mismatch between disordered vestibular input and other sensory signals of orientation, creating a misleading frame of reference and impaired bodily representation in the cortex. This leads to a perception of disembodiment and other “unreal” perceptions [85; 86; 87]. Stimulation of semicircular canals or otoliths can provoke deper- sonalization/derealization symptoms in healthy volunteers with- out a history of depersonalization/derealization [87]. However, depersonalization/derealization symptoms in vestibular patients with anxiety are more frequent, more severe, and qualitatively distinct from symptoms in patients without anxiety. Anxiety is essential to the appearance and intensity of depersonalization/ derealization symptoms in vestibular patients [88]. Out-of-Body Experiences Out-of-body experiences are states in which the individual experiences the center of awareness as located outside his or her physical body, with the sensation of seeing the environ- ment from this elevated vantage point. Persistent vestibular dysfunction disrupts the integration of visual, somatosensory, and vestibular signals. Perceptual incoherence, a byproduct of the resultant visual-vestibular mismatch, can produce an out-of-body experience, with anxiety a significant co-factor in out-of-body experience etiology. In non-dizzy persons, out- of-body experience is associated with depersonalization or derealization symptoms [89]. COGNITIVE FUNCTION Vestibular input activates a broad neural network in the cortex for visuospatial processing and memory. Vestibular function is strongly linked to visuospatial ability—how the mind organizes and understands two- and three-dimensional space. Impaired vestibular input can fundamentally change one’s mental representation of, and awareness of one’s position in, three- dimensional space [70]. Vestibular dysfunction is also implicated in impaired attention, cognitive processing ability, memory, and executive function [70]. This is especially relevant in the elderly, for whom cogni- tive impairment from vestibular dysfunction is broader and more diffuse. It should be considered in any older patient with dizziness or vertigo [90].
POST-TRAUMA OR TOXIC EXPOSURE
POST-CONCUSSIVE AND CERVICOGENIC VERTIGO Patients with post-concussive syndrome or cervicogenic dizzi- ness following a whiplash can experience chronic dizziness with headache, insomnia, cognitive symptoms, or mood lability [62]. Post-Concussion Syndrome In the United States, there are approximately 3.8 million sports-related concussions annually in adolescents and adults. Concussion, the mildest form of traumatic brain injury (TBI), is a transient functional disorder caused by direct trauma, rapid acceleration-deceleration of the head, or blast forces. Post-concussion syndrome persists beyond three months in up to 20% of affected individuals [91]. Headache and dizziness are common symptoms. Other symp- toms include light and sound sensitivity, nausea, tinnitus, cognitive dysfunction (mental fog), problems with visual focus, sleep changes, depression, anxiety, and irritability. Dizziness may be due to the direct CNS effects of the trauma (e.g., axonal injury, other microstructural damage), vestibular migraine, or neuropsychiatric disorders (e.g., anxiety, depres- sion, post-traumatic stress disorder). Post-concussion BPPV is not uncommon. A detailed history and examination are crucial when assessing dizziness in these patients, because treatment should address the underlying etiology [92; 93]. Mild TBI Balance disorders, migraine, and anxiety are also components of mild TBI that appear following exposure to blunt-force or blast trauma, along with symptoms of headache, nausea, vomiting, dizziness/balance problems, fatigue, sleep distur- bances, and difficulty with memory or concentration [91; 93]. Dizziness and headache are reported in more than 70% of cases presenting acutely or chronically post-exposure; vertigo emerges sub-acutely. Other significant sequelae are hearing loss, emergent and delayed post-traumatic balance disorders, and chronic migrainous disorders without radiologic evidence of damage, often accompanied by tinnitus and sensitivity to light or sound [49]. Patients with chronic (at least six months) post-traumatic head injury vestibular symptoms (e.g., imbalance, dizziness) show high rates of multiple peripheral and central vestibular disorders. Despite expert neuro-otologic management, 20% of patients have persistent vestibular symptoms at two years. Treatment-resistant vestibular symptoms in these patients may result from brain trauma-induced impairment of brain plasticity-mediated repair mechanisms [94].
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Book Code: ANCCTX2027
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