Rezeptorfunktion der Bogengänge

Abstract

The perception and conversion of motion stimuli by the vestibular receptors, unimpaired postural control and intact visual acuity are essential for spatial orientation. Disturbances in these three sensory systems can manifest as "vertigo", "dizziness" or "imbalance". The integrity of peripheral receptor function, especially of the three semicircular canals, plays a superficial role. They are sensitive to acceleration stimuli, which they transmit via reflexes to the eye muscles. The stabilization of a visual target is via vestibulo-ocular reflexes, which have a very short latency and thus ensure a permanently stable image on the retina. Modern lateral-specific testing procedures are available to diagnose the receptor function of the peripheral vestibular system. The function of the semicircular canals can be analyzed using a head impulse test (HIT) and, more recently, by means of video-HIT as well as on the basis of a caloric test. Using these techniques, all three semicircular canals can be assessed in a side- and receptor-specific manner.

Clinical experience with video Head Impulse Test in children

“…vHIT is a well-established device in adults which measures the gain of the angular vestibular-ocular reflex (aVOR) during head rotations as the ratio of eye to head acceleration. (2,3) vHIT evaluates the high frequency range of the VOR and can be seen as an advancement of the clinical head impulse test, which has been described by Halmagy and Curthoys in 1988. (4) Today, videooculography systems for evaluating VOR are well-established tools in daily clinical life of neurologists and otolaryngologists which easily, quickly and cost efficiently measure semicircular function in adults.…”

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.…”

“…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 ].…”

“…The development of those modern diagnostic instruments led to a paradigm shift in clinical vestibular diagnostics that increasingly influences the current medical standards of the diagnosis of vertigo and balance disorders [ 37 ]. In Germany, modern methods are more and more established in the outpatient and inpatient ENT-specific sector [ 37 ], [ 38 ], [ 42 ], [ 43 ], [ 44 ], [ 45 ]. The medical benefit of modern diagnostic procedures, their quality and effectiveness are meanwhile scientifically confirmed.…”