Height Vertigo Research Articles

A non-image-forming visual circuit mediates the innate fear of heights in male mice

The neural basis of fear of heights remains largely unknown. In this study, we investigated the fear response to heights in male mice and observed characteristic aversive behaviors resembling human height vertigo. We identified visual input as a critical factor in mouse reactions to heights, while peripheral vestibular input was found to be nonessential for fear of heights. Unexpectedly, we found that fear of heights in naïve mice does not rely on image-forming visual processing by the primary visual cortex. Instead, a subset of neurons in the ventral lateral geniculate nucleus (vLGN), which connects to the lateral/ventrolateral periaqueductal gray (l/vlPAG), drives the expression of fear associated with heights. Additionally, we observed that a subcortical visual pathway linking the superior colliculus to the lateral posterior thalamic nucleus inhibits the defensive response to height threats. These findings highlight a rapid fear response to height threats through a subcortical visual and defensive pathway from the vLGN to the l/vlPAG.

Fear of heights in ancient China

Fear of heights (acrophobia) is defined as a subtype of specific phobias by the DSM-IV TR [1] criteria based on the diagnostic features of panic attacks. It has a lifetime prevalence of 3.1–5.3 % [2]. There is, however, a continuum extending from acrophobia to stimulus-dependent visual height intolerance, which does not fulfill the diagnostic criteria of a specific phobia. The frequency of visual height intolerance (height vertigo) is much higher. A recent epidemiological study based on a representative survey revealed that visual height intolerance has a prevalence of 28 % [3]. Thus, height vertigo is a well-known condition that manifests either as a specific phobia or, if less severe, as visual height intolerance. In their historical review, Balaban and Jacob [4] convincingly describe the comorbidity of vertigo and anxiety as an integral component of the medical literature since antiquity. We found a vivid description of symptoms typical for fear of heights in the Greek Corpus Hippocraticum, 5th century BC [5]: ‘‘When Demokles was with him, he said that he felt his eyesight had worsened, and the muscles in his entire body had slackened. He was, he said, not able to walk along the edge of a precipice or cross over a bridge. He would not dare walk over a ditch, regardless how shallow, for he would be afraid to fall into it. However, he would dare to walk in the ditch itself’’. This raised the question as to whether comparable descriptions can be found in other cultures from nearly the same time period but with a completely different concept of bodily function and disorders, namely in the Chinese medical classics. The 80th chapter (‘Discourse on great confusion’) of the book Huangdi Neijing Lingshu, whose content dates back to between the 2nd century BC and the 2nd century AD [6– 8], provides a lively description of height vertigo. The book is part of the Huangdi Neijing (The internal classic of the Yellow Thearch), the theoretical foundation of Chinese medicine. The Yellow Thearch, Huang Di, is considered the cultural hero who bestowed the gift of medicine on the Chinese people. The chapters of the book are mostly written as interviews between Huang Di and his physicians. In the text, Huang Di asks Qi Bo: ‘‘Often when I climb onto a clear, cold observation platform, after I have gone up half of the steps, look around, and crawl further forward; there is a confusion’’. (Fig. 1) (Clarification: a later commentary refers to the height of the platform as an explanation for this description: ‘‘[its] Qi is cold, it is therefore called ‘a clear, cold platform’.)’’. He continues: ‘‘I feel unusual and inwardly strange, I close my eyes, and then I open them. I calm my mind and steady my breath. A longer time passes, but the confusion does not resolve. Everything spins around and I feel dizzy. I loosen my hair and kneel on the ground, I bow my head, and look down. This [strange feeling] doesn’t stop for a long time. What kind of Qi causes this?’’ Qi Bo replies: ‘‘The essence of the Qi of the five depot-organs and of the six palace-organs all flow upwards to the eyes and give them clarity.(...) The eyelids envelop the essence of the sinews, the bones, the blood and the Qi and together with the vessels they form a connection. At the top it connects to the brain, at the back it comes out in the middle of the neck. If the evil strikes M. Bauer Horst-Gortz-Institute for Theory, History, and Ethics of Chinese Life Sciences, Chariteplatz 1, 10117 Berlin, Germany

Height intolerance: an underrated threat

Fear of heights is considered a variant of specific phobias according to the Diagnostic and Statistical Manual of Mental Disorders [1]. A prospective study reported the prevalence of fear of heights to be 4.9% [2]. There is, however, a continuum extending from acrophobia to stimulus-dependent height intolerance (also called height vertigo), which does not fulfill the diagnostic criteria of a specific phobia [3]. The prevalence of this individual susceptibility has not yet been determined, although its disabling impact on daily life and sport activities is obviously relevant. Therefore, we designed a special questionnaire, based on an Infratest Telephone Master Sample (ITMS) set up for an epidemiologic study and representing the population universe with unbiased samples and without clustering effects. A total of 3,517 German-speaking individuals, aged 14 years and above, selected from households with a fixed-line telephone connection, participated. The main findings are as follows:

A technical eye inspired by biology

It was Erasmus Darwin (1731–1802), the grandfather of Charles Darwin, who first wrote about visual vertigo in his Zoonomia, or, The Laws of Organic Life in 1794: ‘many people, when they arrive at 50 or 60 years of age, are affected with slight vertigo; which is generally but wrongly ascribed to indigestion, but in reality arises from a beginning defect of their sight … these people do not see objects so distinctly as formerly, and by exerting their eyes more than usual they perceive the apparent motions of objects, and confound them with the real motions of them; and therefore cannot accurately balance themselves so as easily to preserve their perpendicularity by them’. Historically, it is remarkable that this description of visual vertigo and its consequences for postural balance date back to a time when vestibular function was not even understood, nearly a century before the publication of Mach's (1875) Fundamentals of the Theory of Motion Perception (Brandt, 1991). Darwin's Zoonomia is a mine of information on early concepts of sensorimotor control of eye movements and multisensory interactions, for example his understanding of height vertigo, which is still appealing: ‘Anyone, who stands alone on the top of a high tower, if he has not been accustomed to balance himself by objects placed at such distances and with such inclinations, begins to stagger, and endeavours to recover himself by his muscular feelings. During this time the apparent motion of objects at a distance below him is very great and the impressions of this apparent motion continue a little time after he has experienced them; and he is persuaded to incline the contrary way to counteract their effects; and either immediately falls, or applying his hands to the building, uses his muscular feeling to preserve his perpendicular attitude, contrary to the erroneous …

Acrophobia and Pathological Height Vertigo: Indications for Vestibular Physical Therapy?

Acrophobia (fear of heights) may be related to a high degree of height vertigo caused by visual dependence in the maintenance of standing balance. The purpose of this case report is to describe the use of vestibular physical therapy intervention following behavioral therapy to reduce a patient's visual dependence and height vertigo. Mr N was a 37-year-old man with agoraphobia (fear of open spaces) that included symptoms of height phobia. Exposure to heights triggered symptoms of dizziness. Intervention. Mr N underwent 8 sessions of behavioral therapy that involved exposure to heights using a head-mounted virtual reality device. Subsequently, he underwent 8 weeks of physical therapy for an individualized vestibular physical therapy exercise program. After behavioral therapy, the patient demonstrated improvements on the behavioral avoidance test and the Illness Intrusiveness Rating Scale, but dizziness and body sway responses to moving visual scenes did not decrease. After physical therapy, his dizziness and sway responses decreased and his balance confidence increased. Symptoms of acrophobia and sway responses to full-field visual motion appeared to respond to vestibular physical therapy administered after completion of a course of behavioral therapy. Vestibular physical therapy may have a role in the management of height phobia related to excessive height vertigo.

Dizziness.

The article gives an overview of the most frequent forms of vertigo, that are of peripheral-labyrinthine, central-vestibular, psychogenic, or physiologic origin. Dizziness or vertigo is a result of a mismatch between 3 sensory systems: the vestibular, the visual, and the somatosensory systems. These systems are mutually interactive and redundant in that orientation and balance are guided by simultaneous reafferent cues. The functional ranges of the systems overlap, thus permitting them to compensate in part for each other's deficiencies. Vertigo is not a well-defined disease entity, but rather a multisensory syndrome induced either by stimulation of the intact sensorimotor system by motion (eg, physiologic vertigo as in motion sickness or height vertigo), or by pathologic dysfunction of any of the stabilizing sensory systems (eg, peripheral vestibular as in vestibular neuritis, or central vestibular as in vertebro-basilar ischemia). The core region in vestibular vertigo syndromes is the vestibulo-ocular reflex, a 3-neuron arc that mediates the information of the semicircular canals and otoliths via the vestibular nerve and vestibular nucleus to the ocular motor nuclei (VI, IV, III) and the supranuclear integration centers in the ponto-mesencephalic brain stem. Clinical phenomena characteristic for physiological and pathologic vertigo syndromes include postural, perceptual, oculomotor, and vegetative syndromes, which manifest with ataxia, nystagmus, vertigo, and nausea. Thus, the clinical testing must include examinations of postural, perceptual, oculomotor, and vegetative dysfunctions.

Background and history of the interface between anxiety and vertigo

The comorbidity of vertigo and anxiety has been an integral component of the medical literature since antiquity. In the works of Plato, the same terms were used in the context of vertigo, inebriation, height vertigo, disorientation, and mental confusion. In classical medicine, vertigo had the ambiguous status of being both a disease per se and a symptom of other diseases such as hypochondriacal melancholy. Further, two etiologies were described for vertigo: an origin in the head (brain) and an origin in the hypochondria (abdominal viscera). In the course of the development of a detailed neurologic taxonomy of vertigo in the latter half of the nineteenth century, a debate ensued whether agoraphobia was a form of vertigo or a distinct psychiatric condition. Elucidation of this forgotten debate, within its historical context, provides insights into the recent rediscovery of the balance–anxiety interface.

Physical and drug therapy for vertigo and ataxia (author's transl)

Vertigo occurs either with motion stimulation which causes an intersensory mismatch or by a dysfunction of one of the stabilizing sensory systems, representing either a "physiological" or a "pathological" vertigo syndrome, respectively. This review emphasizes the differential effects of physical maneuvers and drugs and surgery in the prevention or treatment of motion sickness, height vertigo, head extension vertigo, as well as peripheral labyrinthine lesions, paroxysmal positional vertigo, Menière's syndrome, vertiginous epilepsy and phobic vertigo.

The mechanism of physiological height vertigo. I. Theoretical approach and psychophysics.

A theory is presented supporting a geometrical explanation of physiological height vertigo as a 'distance vertigo' created by visual destabilization of posture when the distance between the observer and visible stationary contrasts becomes critically large. Though height vertigo is generally regarded as a psychopathological process, we hypothesize that it might instead result from an intersensory mismatch when visual information is at variance with vestibular and proprioceptive inputs. Psychophysical experiments confirming the hypothesis revealed that: 1) height vertigo is clearly related to body position, being the greatest in the upright stance; 2) it is the eye-object distance rather than the direction of gaze which is critical; 3) there is a saturation of height vertigo magnitude. Subjective vertigo increases with increasing altitude only below 20 metres. Physiological 'distance vertigo' must be distinguished from psychological 'acrophobia'. Its postural consequences may be ameliorated by strategies gleaned from knowledge of its mechanism such as providing nearby stationary contrasts in the peripheral visual field.

The mechanism of physiological height vertigo. II. Posturography.

In order to validate the hypothesis that height vertigo is based on visual destabilization of free stance when the distance between eye and object becomes critically large, several of its consequences were demonstrated in posturographic experiments: (1) Visual signals conflicting with simultaneous vestibular and somatosensory inputs provided by sinusoidally tilting rooms may destabilize postural sway in the fore-aft as well as in the lateral direction. (2) In natural surrounding sway amplitudes increase with increasing eye-object distance up to 5 meters. Thus, teleologically, subjective height vertigo serves as an appropriate warning signal to withdraw the body from a stimulus situation inducing postural imbalance. (3) Postural height vertigo problems can be alleviated (a) by adjusting the head relative to the gravitational vector, and (b) by the presence of nearby stationary contrasts in the visual periphery according to the dominance of retinal periphery for dynamic spatial orientation.

Height vertigo and human posture.

A theory is presented supporting a geometrical explanation for physiological height vertigo being a distance vertigo through visual destabilization of postural balance when the distance between the eyes and visible stationary contrasts becomes critically large. Physiological and posturographic data obtained under natural height vertigo conditions are consistent with this hypothesis.

"Towards a Lower Paediatric Mortality"

<b>Background and Purpose.</b> Acrophobia (fear of heights) may be related to a high degree of height vertigo caused by visual dependence in the maintenance of standing balance. The purpose of this case report is to describe the use of vestibular physical therapy intervention following behavioral therapy to reduce a patient9s visual dependence and height vertigo. <b>Case Description.</b> Mr N was a 37-year-old man with agoraphobia (fear of open spaces) that included symptoms of height phobia. Exposure to heights triggered symptoms of dizziness. <b>Intervention.</b> Mr N underwent 8 sessions of behavioral therapy that involved exposure to heights using a head-mounted virtual reality device. Subsequently, he underwent 8 weeks of physical therapy for an individualized vestibular physical therapy exercise program. <b>Outcomes.</b> After behavioral therapy, the patient demonstrated improvements on the behavioral avoidance test and the Illness Intrusiveness Rating Scale, but dizziness and body sway responses to moving visual scenes did not decrease. After physical therapy, his dizziness and sway responses decreased and his balance confidence increased. <b>Discussion.</b> Symptoms of acrophobia and sway responses to full-field visual motion appeared to respond to vestibular physical therapy administered after completion of a course of behavioral therapy. Vestibular physical therapy may have a role in the management of height phobia related to excessive height vertigo.