Rezeptorfunktion der Bogengänge

Abstract

Perturbation of semicircular canal function may result in a pathological angular vestibulo-ocular reflex (aVOR). The resulting impairment in gaze stabilization is perceived as "vertigo" or "dizziness" and may occur following receptor function impairment of all three semicircular canals. The head impulse test reveals hidden (covert-catchup) or visible (overt-catchup) saccades in disturbances of semicircular function. Most peripheral vestibular disorders can be treated conservatively. There are surgical treatment options for some diseases, such as intractable benign paroxysmal positional vertigo and superior semicircular canal dehiscence. Vestibular training promotes central reorganization of the VOR. Impaired semicircular receptor function, in particular bilateral vestibulopathy, may affect spatial orientation and cognitive processes. Balance prostheses could serve as a replacement for receptors in the future.

Current diagnostic procedures for diagnosing vertigo and dizziness

“…The test that is not device-related is called the clinical HIT. The technical test is the video head impulse test (video HIT, vHIT) [ 38 ], [ 39 ]. Main components are very light video goggles that are connected with a computer (laptop).…”

“…During those performances and corrections, a sharp image has to be continuously projected on the retina [ 8 ], [ 37 ]. Especially the systems of the eye movement (smooth pursuit, saccadic system, vergence system) and VOR [ 38 ], [ 39 ] contribute to this performance. Because of the short latency of the VOR (about 7–10 ms) and its high dynamic properties, the VOR plays a crucial role for visual stabilization.…”

“…Rotatory test procedures and the video head impulse test reflect middle- and high-frequency properties of the VOR. The understanding of those correlations allows interpreting the test results in the context of disorders of the sense of direction [ 37 ], [ 38 ], [ 39 ].…”

“…If the speed is too low (about <100°/s), the smooth pursuit system may still be active. If the speed is too high (>300°/s), the stimulation might approach zero [ 38 ], [ 39 ]. There should be enough light in the room, the distance between the examiner and the patient should be about an arm’s length.…”

“…The function of the vestibular reflexes cannot only be assessed in a differentiated way, i.e. with regard to topology, but the knowledge that the sense of direction – and especially the vestibulo-ocular reflex (VOR) – works in a broad frequency range (frequency dynamics) led to a new understanding of the outcome of physiological test results [ 36 ], [ 37 ], [ 38 ], [ 39 ], [ 40 ], [ 41 ]. Topological and frequency-specific analyses as well as the assessment of changes in the time course (timely dynamics) were summarized in the concept of a differentiated vestibular functional analysis [ 37 ].…”