Most patients with acute vestibular syndrome have vestibular neuritis or labyrinthitis. Some harbour strokes that can only be differentiated on the basis of subtle eye movement findings, including nystagmus. Peripheral nystagmus should be enhanced by removal of visual fixation. Current bedside methods for removing fixation require expensive equipment or technical skill not routinely available. We sought to test a new method for blocking fixation.
Proof-of-concept study for a new bedside oculomotor diagnostic test using an established physiological measurement of eye movements (electro-oculography (EOG)) as the reference standard. We sampled unselected patients undergoing caloric testing (surrogate model for neuritis) in an academic vestibular clinic. During the brief (30-60 s) decay phase of caloric-induced peripheral vestibular nystagmus, we shone a penlight in the left eye while intermittently occluding the right. We assessed nystagmus intensity (slow-phase velocity) clinically in all subjects and quantified change in two exemplar cases.
Caloric responses frequently decayed before the test was complete, and artefacts rendered many EOGs uninterpretable during the short decay period. A clinically evident increase in nystagmus was seen 18 times in 10 patients and corroborated by EOG in 15. In quantified cases, slow-phase velocity increased as expected (mean change +42%) with fixation blocked.
The penlight-cover test could offer a low-cost, simple means of disrupting visual fixation in clinical settings where differentiating peripheral from central vestibular disorders is crucial, such as the emergency department. Prospective studies are needed to determine the test's utility for excluding dangerous central causes among patients with suspected peripheral lesions.
"Both oculomotor fixation and saccades are typically assessed with the use of several clinical tools, including manual visual inspection , nystagmography, and computerized infrared pupillary tracking devices , , . Several methods are available to automate the analysis and classification process of oculomotor data, including the velocity threshold identification (I-VT), hidden Markov model identification (I-HMM), minimum spanning tree identification (I-MST) , and Kalman filter identification (I-KF) , . "
[Show abstract][Hide abstract] ABSTRACT: In an effort toward standardization, this paper evaluates the performance of five eye-movement classification algorithms in terms of their assessment of oculomotor fixation and saccadic behavior. The results indicate that performance of these five commonly used algorithms vary dramatically, even in the case of a simple stimulus-evoked task using a single, common threshold value. The important contributions of this paper are: evaluation and comparison of performance of five algorithms to classify specific oculomotor behavior; introduction and comparison of new standardized scores to provide more reliable classification performance; logic for a reasonable threshold-value selection for any eye-movement classification algorithm based on the standardized scores; and logic for establishing a criterion-based baseline for performance comparison between any eye-movement classification algorithms. Proposed techniques enable efficient and objective clinical applications providing means to assure meaningful automated eye-movement classification.
[Show abstract][Hide abstract] ABSTRACT: In der Notfallambulanz gilt es im Wesentlichen die drei häufigsten peripher-vestibulären Erkrankungen sicher zu erkennen:
die Neuropathia vestibularis, der bénigne paroxysmale Lagerungsschwindel und der Morbus Méni ère (1). Je zuverlässiger diese
drei Krankheitsbilder erkannt werden, umso sicherer lassen sich abweichende Charakteristika als Warnzeichen deuten, z. B.
ein zentraler Schwindel bei einem Insult. In diese Richtung zielt auch die Arbeit von Barraclough und Bronstein (2). Die Autoren
schlagen eine standardisierte Prüfung vor, um effektiv und mit einfachen Mitteln zu einer sicheren differentialdiagnostischen
Entscheidung zu gelangen. Eine kurzgefasste, gute Übersicht der wesentlichen Differentialdiagnostik bietet die Arbeit von
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