G. De Wit

Posturography as an Auxiliary in Vestibular Investigation

Posturography, the recording of the way in which man stands upright, proves to be a useful auxiliary in vestibular investigation. The authors divide this posturography into “spot stabilometry” (or statokinesimetry, SKG) and “linear stabilometry” (or stabilometry, STG). Special attention is paid to the linear stabilometry (STG). The low-frequency-sway of ca 0.2 Hz is nearly pathognomonic for vestibular stimulation. In the spot stabilogram (SKG), the area of the spot and the place of the spot in relation to the centre are of interest.

Atresia Auris Minima

Four cases of atresia auris are described, in which the atresia was only based on an abnormality in the chain of auditory ossicles. This possibility should be borne in mind when one is dealing with an unexplained conduction deafness existing since childhood. The name of atresia auris minima is suggested for this group. For some cases an operative technique, called by the author “reconstruction of the hammerhead columella”, is recommended.

The “Marche-En-Étoile” Revised: The Influence of After-Images and Prism-Glasses on Starwalks

An analysis of the role that casual after-images play in starwalk (marche-en-étoile) tests, shows that these can be turned from unreliable into reliable tests. The vestibular function test described in this article is as follows: (a) the individual walks with open eyes to a point of reference 5 m distant. On arrival, he closes his eyes and walks backward and forward according to the marche-en-étoile procedure. (b) Same procedure as (a), but now the orientation point is replaced by a light source that is switched off when the patient reaches it. (c) Same procedure as (b), but now the patient is wearing prism-glasses. It turns out, the deviations in the starwalk are caused mainly by drifting of the after-image. This drift is based on an oculogyral illusion, and it appears that it can be influenced by wearing prism-glasses. These investigations reveal the existence of hitherto too little known interactions between the vestibular and the visual system.

Investigations of a certain class of linear complementarity problems

A certain class of linear complementarity problems that appeared in an economical study concerning self-employment is investigated. The principal findings for this class of linear complementarity problems are: (i) there is always a solution, which can be found by the Lemke algorithm; (ii) characterizations are found for solutions, some typical for all solutions, some typical for locally nonunique solutions, and some typical for locally unique solutions; (iii) a sufficient condition is found to guarantee a globally unique solution.