Biomedical subjects

Mieke Hoppenbrouwers

Publications and source records attributed to Mieke Hoppenbrouwers.

3 recordsLinked to original sources

PubMed2004

Suppression of the E-effect during the subjective visual vertical test.

The subjective visual vertical was measured in 38 healthy subjects. The head was alternately roll-tilted to the right and to the left, and the start position of the light bar was alternately set clockwise and counterclockwise. When the head is tilted less than 60-70 degrees a deviation of the subjective visual vertical in the opposite direction to the head tilt is expected. This phenomenon has been reported in various studies as the E-effect. The present study demonstrates however that the E-effect is suppressed if the start position of the light bar is presented relatively parallel to the length axis of the tilted head.

Adolescent↗

PubMed2003

The interutricular distance determined from external landmarks.

Knowledge of the exact distance between the utricles is important in new vestibular tests, such as the unilateral centrifugation (UC) test for the unilateral examination of the utricles. During this test, subjects are rotated at constant velocity and simultaneously laterally displaced along an interaural axis so that one labyrinth becomes aligned with the axis of rotation. When the axis of rotation crosses precisely through one labyrinth, only the opposite labyrinth is stimulated. To achieve this setup, precise knowledge of the interutricular distance is needed. The purpose of this study is to investigate the correlation between the interutricular distance (IUD), measured on T2-weighted magnetic resonance images, and specific external measures of head dimensions such as distance nasion-inion, intermastoid distance (IMD), distances between the temporomandibular joints and between the lateral margins of the orbits. Data have been collected in a series of 50 subjects (25 men and 25 women). On MR images we found a mean IUD of 7.22 cm (SD = 0.42 cm). There was a strong correlation between the IUD measured on MR images and the intermastoid distance. A linear combination of the IMD, nasion-inion distance and height of the subjects could predict the IUD very satisfactory (R = 0.85, adjusted R2=0.723). We also determined a measure of eccentricity of the vestibular labyrinths. The 95% prediction interval for the asymmetry appeared to be less than 4.3%.

Adolescent↗

PubMed2003

Utricular sensitivity and preponderance assessed by the unilateral centrifugation test.

Utricular sensitivity and preponderance of the right or left utricle can be assessed by means of the unilateral centrifugation test. In this test, subjects are rotated about an earth vertical axis at a velocity of 400 degrees per second. During the ongoing rotation, the subject is gradually translated 4 cm first to the right, and then to the left, along an interaural axis, to a position at which one utricle becomes aligned with the axis of rotation, and at this point is subjected only to gravitational forces. At this eccentric position, the contralateral utricle is exposed to the combination of gravity and a centrifugal acceleration of 0.4g, corresponding to an apparent roll-tilt of 21.7 degrees. This stimulus induces ocular counterrolling (OCR), which is measured on-line using three-dimensional video-oculography (VOG). We observed that ocular counterrolling appears as a linear function of the gravito-inertial acceleration tilt of the head centre (GIA(HC)) during the lateral translation. We present a theoretical model for this linear relationship that contains two parameters: 1) the slope of the linear regression is a measure for the utricular sensitivity and 2) the intercept of the linear regression is a measure of the preponderance of the right or left utricle. The strength of the model is supported by data obtained from 28 healthy subjects and 14 patients with unilateral vestibular deafferentiation (UVD) due to acoustic neuroma surgery.

Acceleration↗