Chronische Schwindelerkrankungen sind häufig und stellen wegen der vielfältigen Ursachen eine diagnostische und therapeutische Herausforderung dar. Eine möglichst genaue Anamnese kann, durch neurologische und neurootologische Untersuchungen ergänzt, die Ursachen meist gut eingrenzen. In diesem Beitrag werden im Detail durch afferente Schädigungen und durch Vestibulopathien verursachte sowie funktionelle Schwindelstörungen beschrieben.

Subjective adaptation to image tilt in the sagittal axis is a physiological phenomenon and can be observed during head tilt to the shoulder. Oculomotor adaptation has been found to have a minor influence. Nevertheless, contours are perceived as vertically and horizontally aligned even though they do not fall on the vertical and horizontal anatomic-geometric retinal meridians. Unilateral macular translocation with surgical rotation of the macula around the optic nerve head on to a healthier retinal pigment epithelium leads to similar torsional misalignment of the retinal meridians. To analyse the mechanisms of adaptation to image tilt without superimposition of binocular problems, we followed two monocular patients after macular translocation with upward rotation of the fovea in their left eyes (incyclorotation). In both cases, in spite of subjective adaptation of the visual system, a pronounced head and body tilt to the side of the operated eye (here to the left) developed. This is the first report on a medical procedure demonstrating an impressive ability to coordinate head and eye position during retinal image tilt.

Objective: A characteristic feature of spinocerebellar ataxia type 2 (SCA2) is saccadic slowing at early disease stages. We sought to determine whether this sign is detectable before clinical manifestation and quantifies the disease progression throughout life in linear fashion.Methods: In a specialized ataxia clinic, 54 presymptomatic carriers of SCA2 polyglutamine and expansions and 56 relatives without mutation were documented with regard to their maximal saccade velocity (MSV).Results: Among the control individuals, a significant effect of aging on MSV was observed. After elimination of this age influence through a matched-pair approach, a presymptomatic decrease of MSV could be shown. The MSV reduction was stronger in carriers of large expansions. In the years before calculated disease manifestation, the MSV impairment advanced insidiously.Conclusion: Saccade velocity is a sensitive SCA2 endophenotype that reflects early pontine degeneration and may be a useful diagnostic parameter before the onset of ataxia.Significance: Future neuroprotective therapies of polyglutamine neurodegeneration may be assessed by MSV from earliest to prefinal disease stages. (C) 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Die spinozerebelläre Ataxie Typ 2 (SCA2) gehört zu den Polyglutaminerkrankungen und kann sich klinisch als Form eines autosomal dominanten Dopa-responsiven Parkinsonoids einhergehend mit einer frühen Degeneration des nigrostriatalen Systems präsentieren. Darüber hinaus findet man bei SCA2-Patienten neben einer Ataxie und Dysarthrie eine Verlangsamung der Blicksakkaden. Zur Evaluierung als möglichen Surrogatmarker untersuchten wir bei 82 SCA2-Patienten und 80 Kontrollen die Sakkadengeschwindigkeit und korrelierten diese zur Polyglutamin-Expansionslänge, Erkrankungsdauer und einem klinischen Ataxie Score.

A bstract : We measured in 82 spinocerebellar ataxia type 2 (SCA2) patients and in 80 controls maximal saccade velocity (MSV) and correlated it to polyglutamine expansion size and disease duration. MSV is strongly decreased in SCA2 patients and is influenced mostly by polyglutamine size.

We assessed maximal saccade velocity (MSV) in 82 spinocerebellar ataxia type 2 (SCA2) patients and 80 controls, correlating it to disease duration, polyglutamine expansion size, age at onset, ataxia score, age, and sex. Little overlap with normal values was found even at earliest stages. Stepwise linear regression analysis showed that 60-degree MSV was strongly influenced by polyglutamine size and less by disease duration, whereas the reverse was found for ataxia score. Saccade velocity thus is a sensitive, quite specific, and objective endophenotype, useful to search polyglutamine modifier genes.

Background: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant inherited disorder which is clinically characterized by progressive cerebellar ataxia, dysarthria, neuropathy and early slowing of horizontal saccadic eye movements. The underlying mutation is an unstable expansion of a polyglutamine domain within the protein ataxin-2. The prevalence of SCA2 is particulary high in Holguín province, Cuba.

This chapter examines some of the ways in which a basic motor act, the vestibuloocular reflex, can be considered. It takes its inspiration in part from Dr Ian Howard. Ian’s functional approach with his emphasis on explanation-by-demonstration, has been hugely influential on the first author. Which frame of reference is used by the reflexes that tend to maintain gaze during head movements is a question to which the answer has tended to be unnecessarily constrained by the anatomically rigid frame of the vestibular end organ embedded in the skull. Neural processes have no such constraint and indeed the frame they use cannot be based in the head since it is not possible to code head movement in a head-based co-ordinate system (Harris, 1997; Harris, Zikovitz and Kopinska, 1998). Here we model the eye movements evoked while rotating around various axes, as the output of a system consisting of three channels. The orientations of the channels needed to best model the eye movements evoked by rotation before and after an adaptation procedure have been determined. One was found close to the roll direction with the other two roughly in Listing’s plane, and approximately equidistant from all three canal pairs.

Different sensory systems (e.g. proprioception and vision) have a combined influence on the perception of body orientation, but the timescale over which they can be integrated remains unknown. Here we examined how visual information and neck proprioception interact in perception of the “subjective straight ahead” (SSA), as a function of time since initial stimulation. In complete darkness, healthy subjects directed a laser spot to the point felt subjectively to be exactly straight ahead of the trunk. As previously observed, left neck muscle vibration led to a disparity between subjective perception and objective position of the body midline, with SSA misplaced to the left. We found that this displacement was sustained throughout 28 min of continuous proprioceptive stimulation, provided there was no visual input. Moreover, prolonged vibration of neck muscles leads to a continuing disparity between subjective and objective body orientation even after offset of the vibration; the longer the preceding vibration, the more persistent the illusory deviation of body orientation. To examine the role of vision, one group of subjects fixated a central visual target at the start of each block of continuous neck vibration, with SSA then measured at successive intervals in darkness. The illusory deviation of SSA was eliminated whenever visual input was provided, but returned as a linear function of time when visual information was eliminated. These results reveal: the persistent effects of neck proprioception on the SSA, both during and after vibration; the influence of vision; and integration between incoming proprioceptive information and working memory traces of visual information.

Background The standard techniques for the screening and staging of internal carotid artery (ICA) stenosis are Doppler (continuous wave) and Duplex sonography. For the imaging of ICA occlusive disease, magnetic resonance angiography (MRA) is replacing digital subtraction angiography (DSA). The purpose of this observational study was to assess whether contrast enhanced MRA (CE-MRA) combined with ultrasound provided sufficient information for the planning of surgical treatment. Methods CE-MRA was performed in 195 patients (mean age 67.5 years) with sonographic evidence of severe ICA stenosis. The MRA examination protocol contained a heavily T1-weighted contrast bolus enhanced 3D-gradient echo sequence. The degree of stenosis was estimated retrospectively by two experienced neuroradiologists who were blinded to the sonographic findings. Results The consistency of MRA and ultrasound was sufficient to plan thrombendarterectomy in 182/195 patients. The estimations of the degree of stenosis were congruent between MRA and ultrasound in 91 % of 197 vessels with high-degree carotid artery stenosis. CE-MRA evaluation had a high interobserver agreement. In 3 cases ultrasound examination diagnosed a filiform ICA stenosis which was not visible with MRA. In all these cases, DSA and the intraoperative findings revealed very short (1–2 mm), high-grade, excentric stenosis. CE-MRA correctly detected patency in 5 patients with high-grade and low-flow carotid artery stenosis, which had been regarded as occluded by ultrasound. Conversely with, in CE-MRA two occluded vessels were falsely considered as open. Conclusions The combination of sonography and CE-MRA is a powerful tool for the non-invasive presurgical evaluation of the carotid arteries. DSA should be reserved for selected cases.

To achieve stereoscopic vision, the brain must search for corresponding image features on the two retinas1. As long as the eyes stay still, corresponding features are confined to narrow bands called epipolar lines2,3. But when the eyes change position, the epipolar lines migrate on the retinas4,5,6. To find the matching features, the brain must either search different retinal bands depending on current eye position, or search retina-fixed zones that are large enough to cover all usual locations of the epipolar lines. Here we show, using a new type of stereogram in which the depth image vanishes at certain gaze elevations, that the search zones are retina-fixed. This being the case, motor control acquires a crucial function in depth vision: we show that the eyes twist about their lines of sight in a way that reduces the motion of the epipolar lines, allowing stereopsis to get by with smaller search zones and thereby lightening its computational load.

Zusammenfassung Durch die unterschiedliche Ischämietoleranz von innerer Kapsel und Stammganglien kann es bei einem passageren Verschluss des Hauptstamms der Arteria cerebri media zu einer selektiven Nekrose der Stammganglien kommen. Klinische Symptome sind in diesen Fällen gering ausgeprägt. Bei erhaltener Kapsel tritt keine Hemiparese auf. Wir berichten über den Fall eines Patienten, der infolge eines Stammganglieninfarkts bei erhaltener Pyramidenbahn eine passagere Hemichorea entwickelte, die sich spontan nach 48 Stunden weitgehend zurückbildete. Thalamus und Nucleus subthalamicus waren nicht von dem ischämischen Infarkt betroffen.

The 3D orientation and amplitude of the movement of each eye evoked by predictable, sinusoidal and non-predictable, sum-of-sines rotation about roll, yaw, pitch and intermediate axes were measured in seven subjects. The rotation axis of the eyes was not always perfectly aligned with the stimulus axis but showed systematic deviations that depended on the orientation of the rotation axis of the head. Misalignment of the oculomotor response with the stimulus axis is equivalent to adding an orthogonal, non-compensatory vector that potentially could introduce retinal slip, rather than compensate for it. The variations in orientation could not be readily explained as an artifact arising from the differential processing of the roll component. Instead, differences in the movements of the left and right eyes had trends appropriate for compensating for the geometrical demands of the translation of the eyes that must necessarily accompany natural head rotation.

We recorded three-dimensional eye movements elicited by velocity steps about axes that were tilted with respect to the earth-vertical. Subjects were accelerated in 1 s from zero to 100°/s, and the axis of rotation was tilted by 15°, 30°, 60°, or 90°. This stimulus induced a constant horizontal velocity component that was directed opposite to the direction of rotation, as well as a modulation of the horizontal, vertical and torsional components with the frequency of the rotation. The maximum steady-state response in the horizontal constant-velocity component was much smaller than in other species (about 6°/s), reaching a maximum at a tilt angle of about 60°. While the amplitude of the horizontal modulation component increased up to a tilt angle of 90° (8.4°/s), the vertical and torsional modulation amplitudes saturated around 60° (ca. 2.5°/s). At small tilt angles, the horizontal modulation component showed a small phase lag with respect to the chair position, which turned into a small phase lead at large tilt angles. The torsional component showed a phase lead that increased with increasing tilt angle. The vertical and torsional velocity modulation at large tilt angles was not predicted by a recent model of otolith-canal interaction by Merfeld. Agreement between model and experimental data could be achieved, however, by introducing a constant force along the body's z-axis to compensate for the gravitational pull on the otoliths in the head-upright position. This approach had been suggested previously to explain the direction of the perceived subjective vertical during roll under different g-levels, and produced in our model the observed vertical and torsional modulation components at large tilt angles.

The eye muscles in humans are arranged in such a way that they allow rotations of the globe about any axis in three-dimensional space. With the recent availability of modern 3D eye movement measurement techniques and the further development of appropriate mathematical descriptions we are now able to study eye movements in all three degrees of freedom. This article describes the basic mathematical tools for 3D eye movement analysis as well as advantages and disadvantages of different measurement techniques, in a second part some clinical applications are presented. The close coupling between the vestibular and the oculomotor system suggests that by measuring spontaneous and elicited eye movements in 3D in the case of an acute unilateral vestibular pathology we might be able to find out which parts of the vestibular system are affected. The rational of such an analysis is based on the observation that electrical stimulation of single semicircular canal afferents in animals induce eye movements which lie roughly in the plane of the canal. It is, therefore, possible to deduct which canals cause the eye movements observed when only some parts of the vestibular system are defective. Thus, the analysis of 3D eye movements has the potential to significantly improve our diagnostic capabilities.

ResumenInformamos sobre un paciente con trastorno esquizoafectivo que estaba en terapia de combinación con litio, carbamazepina y el neuroléptico trifluperidol. El paciente experimentó una pneumonía lobular y desarrolló un deterioro cerebelar agudo y persistente que se debía muy probablemente a la toxicidad del litio, aunque el nivel de litio en el suero estaba dentro del rango terapéutico. La combinación de litio, carbamazepina y neurolépticos es común, y generalmente se considera que es segura. El caso del que se informa indica que este régimen podría aumentar el riesgo de intoxicación, con efectos secundarios potencialmente discapacitantes.