Functional loss of the horizontal doll's eye reflex following unilateral vestibular lesions

Abstract

The doll's eye reflex represents the vestibulo-ocular reflex (VOR) elicited by high-acceleration head rotation. After complete unilateral vestibular lesions, the ipsilateral, horizontal doll's eye reflex is replaced by a series of "catch-up" saccades. These cause permanent symptoms of blurred vision and dizziness during ipsilateral turns. We compared normal controls and patients with complete surgical lesions or canal paresis of up to 9 years duration via electronystagmography (ENG) to determine the usefulness of the doll's eye test as a diagnostic test for complete vestibular lesions. This test was found to be more sensitive in diagnosis of such lesions than head-shaking nystagmus, rotatory directional preponderance, and spontaneous nystagmus. It is also useful to document VOR function in patients in whom caloric irrigation is contraindicated.

Normative Data and Test-Retest Reliability of the SYNAPSYS Video Head Impulse Test

“…As the caloric test is considered the gold standard test of horizontal SCC function, especially for the identification of unilateral vestibular losses, it has been used as the reference standard to evaluate the performance of the HIT. The bedside HIT has been shown to have a sensitivity of 100% and specificity ranging from 97 to 100% in cases of vestibular nerve sections (Foster et al, 1994;Lehnen et al, 2004;Cremer et al, 1998;Halmagyi and Curthoys, 1988). In less severe cases of vestibular loss, however, the sensitivity and specificity are reduced with sensitivity ranging from 34 to 75% (average 5 51%) and specificity ranging from 82 to 97% (average 91%) (Harvey and Wood, 1996;Harvey et al, 1997;Beynon et al, 1998;Pé rez and Rama-Lopez, 2003;Schubert, et al, 2004).…”

Diagnostic accuracy of acute vestibular syndrome at the bedside in a stroke unit

“…Caution is required when comparing hHIT to caloric testing, as each tests a different frequency property of the vestibulo-ocular reflex [29]. Overall hHIT has a sensitivity of 35-100% and a specificity of 95-100% [6,10] against caloric testing depending on the population studied. A negative hHIT maybe seen in 8-18% of VN [4,23], and this maybe because more than 50% of canal paresis is needed for hHIT to be positive [11], the presence of inferior VN [1], or covert saccades that are imperceptible to the examiners [33].…”

Motorized head impulse rotator in patients with vestibular schwannoma

“…The test evaluates the operative range of the VOR used during natural locomotion, and it relies on Ewald?s second law, which states that there is a large asymmetry between excitatory and inhibitory responses of a semicircular canal [2]. It allows unilateral evaluation of the vestibular function, although subjective detection, whether fast refixation saccade occurs, may be difficult [3,4].…”