Prolonged Positional Downbeat Nystagmus in Benign Paroxysmal Positional Vertigo: A Case Report and Literature Review

Purpose This study aimed to report an unusual case of benign paroxysmal positional vertigo (BPPV), who showed prolonged positional downbeat nystagmus without latency and was diagnosed with cupulolithiasis of the anterior canal (AC). We compared this case with one of typical AC-BPPV, and possible mechanisms underlying the atypical characteristics were discussed. Method Two patients diagnosed with AC-BPPV were reported. Positional testing using video-oculography goggles was performed, and outcomes were measured via medical records and analysis of videos of the nystagmus. Results Downbeat nystagmus was observed in the contralateral Dix–Hallpike test in both cases. The torsional component was subtle or absent, but motion was induced toward the affected ear. The two cases differed in latency and duration of vertigo, as well as habituation. The patient with atypical nystagmus showed little or no latency and longer duration. Moreover, there was no habituation on repeated tests. The nystagmus showed several differences from that of typical AC-BPPV. Conclusions Based on our case, AC-BPPV may induce various unusual clinical manifestations of nystagmus. Accurate diagnosis requires careful consideration of the patient's symptoms and the characteristics of the nystagmus. Supplemental Material https://doi.org/10.23641/asha.14265356

Clinical and VNG Features in Anterior Canal BPPV—An Analysis of 13 Cases

Objective: To define diagnostic VNG features in anterior canal BPPV during positional testing (Dix-Hallpike, supine head hanging, and McClure Pagnini tests).Study Design: A retrospective study of patients diagnosed with anterior canal BPPV across four referral centers in New Delhi, Kochi, Bangalore, and Dubai.Subjects and Methods: Clinical records of 13 patients with AC BPPV out of 1,350 cases, during a 3-years period, were reviewed and analyzed by four specialists.Results: Four patients had positional down beating nystagmus with symptoms of vertigo during the bilateral DHP maneuver. Seven cases had positional down beating nystagmus only on one side of DHP. Typical down beating nystagmus was seen in 10 out of 13 cases during the straight head hanging maneuver. Down beating torsional nystagmus was seen in 6 out of 13 cases. Down beating with horizontal nystagmus was seen in three cases (in DHP and MCP mainly) while pure down beating nystagmus during SHH was only seen in four cases.Conclusion: We conclude that anterior canal BPPV is a rare but definite entity. It may not be apparent on positional testing the first time, so repeated testing may be needed. The most consistent diagnostic maneuver is SHH though there were patients in which findings could only be elicited using DHP testing. We recommend a testing protocol that includes DHP testing on both sides and SHH. MCP testing may also evoke DBN with or without the torsional component. Reversal of nystagmus on reversal of testing position is unusual but can occur. The Yacovino maneuver is effective in resolving AC BPPV. We also propose a hypothesis that explains why DHP testing is sensitive to AC BPPV on either side, whereas MCP lateral position on one side is only sensitive to AC BPPV on one side. We have explained a possible role for the McClure Pagnini test in side determination and therapeutic implications.

Head-Shaking Nystagmus in Posterior Canal Benign Paroxysmal Positional Vertigo with Canalolithiasis

Background: There have been several studies about head-shaking nystagmus (HSN) in posterior canal benign paroxysmal positional vertigo (PC-BPPV). The purpose of the study was to determine the characteristics of HSN and its relationship with head-bending nystagmus (HBN) and lying-down nystagmus (LDN) in PC-BPPV and to suggest a possible pathomechanism of HSN based on these findings. Methods: During the study period, 992 patients with BPPV were initially enrolled. After excluding horizontal or anterior canal BPPV, multiple canals involvement, secondary causes of BPPV, identifiable central nervous system (CNS) disorders, unidentifiable lesion side, or poor cooperation, 240 patients with unilateral PC-BPPV were enrolled. We assessed the frequency, pattern of HSN, and correlation with other induced nystagmus after positional maneuvers such as head bending, lying down, head-turning, and Dix-Hallpike test. Results: Approximately 32% of patients with PC-BPPV showed HSN. Among patients with HSN, approximately 61% of patients showed predominantly downbeat nystagmus, and two-third of them had a torsional component. The torsional component was mostly directed to the contralesional side. Horizontal nystagmus (36%) and upbeat nystagmus (3%) were also observed after head-shaking in PC-BPPV. The presence of HSN was significantly correlated with that of HBN in PC-BPPV (p = 0.00). The presence of a torsional component of HSN was also significantly correlated with that of HBN in PC- BPPV (p = 0.00). Discussion: Perverted HSN, a typical sign of central vestibulopathy, is common in posterior canal BPPV and related to HBN. For generating HSN in PC-BPPV, the otolithic movements related to the endolymph dynamics seem to be more important than the velocity storage mechanism.

Torsional component of microsaccades during fixation and quick phases during optokinetic stimulation

While many studies have characterized the eye movements during visual fixation, including microsaccades, in most cases only horizontal and vertical components have been recorded and analyzed. Thus, little is known about the torsional component of microsaccades. We took advantage of a newly developed software and hardware to record eye movements around the three axes of rotation during fixation and torsional optokinetic stimulus. We found that the average amplitude of the torsional component of microsaccades during fixation was 0.34 ± 0.07 degrees with velocities following a main sequence with a slope comparable to the horizontal and vertical components. We also found the size of the torsional displacement during microsaccades was correlated with the horizontal but not the vertical component. In the presence of an optokinetic stimulus a nystagmus was induced producing a more frequent and larger torsional quick phases compared to microsaccades produced during fixation with a stationary stimulus. The torsional component and the vertical vergence component of quick phases grew larger with higher velocities. Additionally, our results validate and show the feasibility of recording torsional eye movements using video eye tracking in a desktop mounted setup.

The Geometry and Mechanics of Insect Wing Deformations in Flight: A Modelling Approach

The nature, occurrence, morphological basis and functions of insect wing deformation in flight are reviewed. The importance of relief in supporting the wing is stressed, and three types are recognized, namely corrugation, an M-shaped section and camber, all of which need to be overcome if wings are to bend usefully in the morphological upstroke. How this is achieved, and how bending, torsion and change in profile are mechanically interrelated, are explored by means of simple physical models which reflect situations that are visible in high speed photographs and films. The shapes of lines of transverse flexion are shown to reflect the timing and roles of bending, and their orientation is shown to determine the extent of the torsional component of the deformation process. Some configurations prove to allow two stable conditions, others to be monostable. The possibility of active remote control of wing rigidity by the thoracic musculature is considered, but the extent of this remains uncertain.

V1 neurons encode the perceptual compensation of false torsion arising from Listing’s law

We try to deploy the retinal fovea to optimally scrutinize an object of interest by directing our eyes to it. The horizontal and vertical components of eye positions acquired by goal-directed saccades are determined by the object’s location. However, the eccentric eye positions also involve a torsional component, which according to Donder’s law is fully determined by the two-dimensional (2D) eye position acquired. According to von Helmholtz, knowledge of the amount of torsion provided by Listing’s law, an extension of Donder’s law, alleviates the perceptual interpretation of the image tilt that changes with 2D eye position, a view supported by psychophysical experiments he pioneered. We address the question of where and how Listing’s law is implemented in the visual system and we show that neurons in monkey area V1 use knowledge of eye torsion to compensate the image tilt associated with specific eye positions as set by Listing’s law.

Lack of Torsion in the Type-III Duane Retraction Syndrome (DRS-III) Affected Left Eye During Dix -Hallpike Test

Background Duane retraction syndrome (DRS) is a congenital cranial dysinnervation disorder (CCDD) of ocular movements, characterized by deficits in horizontal duction associated with narrowing of palpebral fissure, retraction of eye globe on attempted adduction and occasionally accompanied by upshoot or downshoot of the eye globe. It is caused by congenital absence of sixth cranial nerve, which results in fibrotic changes in the extraocular muscles leading to an abnormal ocular motility--a concept known as CCDD. Depending on whether only abduction/adduction or both are affected, DRS has been classified into three types designated as type-I, type-II and type-III. The torsional movements of the affected eye in DRS have not been reported to be deficient hitherto, which could be due to difficulties in the routine bedside evaluation of such movements. Case Presentation An unusual case of a patient of left unilateral type-III DRS is reported, who presented with a short history of vertigo on getting up from supine to sitting position and on assuming right lateral recumbent position. The diagnostic right Dix-Hallpike test (DHT) revealed upbeating torsional geotropic positioning nystagmus in the normal right eye and upbeating positioning nystagmus without torsional component in the abnormal left eye and this clinical finding was video recorded. Conclusion The observed lack of incyclotorsion of the left eye, affected with DRS-III during right Dix-Hallpike positioning, is primarily due to the absence of initial slow-phase excyclotorsional component. If the slow phase of VOR does not occur, then the fast-phase VOR, which is a refixation saccade, will be lacking too. An anastomosis, either in the lateral wall of the cavernous sinus or within the orbit, between the trochlear nerve and fibers of the oculomotor nerve can lead to simultaneous co-contraction of the inferior and superior oblique muscles. This is the most probable explanation for such finding of asymmetrical absence of torsional component in the left eye affected by DRS-III, during right Dix -Hallpike positioning. Thus, the recording of eye movements (voluntary and involuntary) opened a window into the brain to conceptualize neural and mechanical factors influencing the human eye movements.

Multiple Sclerosis Presenting as an Anterior Semicircular Canal Benign Paroxysmal Positional Vertigo: Case Report

We present the case of a 31-year-old woman with isolated symptomatology accusing positional vertigo. The videonystagmography (VNG) including Dix-Hallpike testing we have performed, highlighted atypical eye movements. We have observed a positional downbeating nystagmus with characteristics that could be accounted for anterior semicircular canal benign paroxysmal positional vertigo. Furthermore, examining the atypical nystagmus at the measurements performed during VNG recordings, we suspicioned a central positional vertigo. The abnormalities observed at the positional nystagmus were the lack of latency period, the downbeating component not limited in time, and the atypical torsional component. The magnetic resonance imaging examination recommended showed multiple white matter lesions characteristic for multiple sclerosis. The patient was referred to the neurology department for further evaluation and treatment. The diagnosis was unexpected because the patient did not have any other symptom that could have been linked to multiple sclerosis.