Penlight-cover test: a new bedside method to unmask nystagmus
ABSTRACT 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.
- SourceAvailable from: Oleg Komogortsev[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.IEEE Transactions on Biomedical Engineering 12/2010; 57(11-57):2635 - 2645. DOI:10.1109/TBME.2010.2057429 · 2.23 Impact Factor
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ABSTRACT: Acute dizziness is a frequent index symptom in the emergency department as well as in the rural practice office. Most acute dizziness, however, is not dangerous, but some types are highly dangerous. Clinical routine acute dizziness can be separated into frequent benign syndromes including benign paroxysmal positional vertigo (BPPV), vestibular neuritis, Meniθre's disease or vestibular migraine, and what is here referred to as the "white shark" of dizziness, i.e. a stroke in the posterior circulation or more rarely a tumor in the posterior fossa. A practical concept is presented to clarify most frequent acute dizziness syndromes using clinical and low budget methods.04/2015; 6(2):272-6. DOI:10.4103/0976-3147.153238
Article: Nystagmus and saccadic intrusions.[Show abstract] [Hide abstract]
ABSTRACT: We review current concepts of nystagmus and saccadic oscillations, applying a pathophysiological approach. We begin by discussing how nystagmus may arise when the mechanisms that normally hold gaze steady are impaired. We then describe the clinical and laboratory evaluation of patients with ocular oscillations. Next, we systematically review the features of nystagmus arising from peripheral and central vestibular disorders, nystagmus due to an abnormal gaze-holding mechanism (neural integrator), and nystagmus occurring when vision is compromised. We then discuss forms of nystagmus for which the pathogenesis is not well understood, including acquired pendular nystagmus and congenital forms of nystagmus. We then summarize the spectrum of saccadic disorders that disrupt steady gaze, from intrusions to flutter and opsoclonus. Finally, we review current treatment options for nystagmus and saccadic oscillations, including drugs, surgery, and optical methods. Examples of each type of nystagmus are provided in the form of figures.Handbook of Clinical Neurology 01/2011; 102:333-78. DOI:10.1016/B978-0-444-52903-9.00019-4