Characteristics Of Nystagmus Research Articles

Dizzy and Psychological Scales in Benign Paroxysmal Positional Vertigo: Suspicious Patients without Characteristic Nystagmus

Objectives Patients, who have had a history of benign paroxysmal positional vertigo (BPPV)-like symptoms, but no characteristic nystagmus, were often present. They are diagnosed as having a resolved state from BPPV or normal, and tend to be overlooked. We investigated the dizzy and psychological scales in BPPV-suspicious patients. Methods Thirty-nine patients, which they had vertigo of a short duration at the specific head position, and clinically suspicious BPPV, but no nystagmus in positional tests, were enrolled. We compared dizzy and psychological scales of suspicious BPPV patients with 138 BPPV patients, using dizziness handicap inventory (DHI), the beck depression inventory (BDI), and the Spielberger state-trait anxiety inventory. Additionally, among the BPPV-suspicious group, patients with a BPPV history were compared with those with no previous BPPV. Results No differences in the all scales were found between the two groups. However, DHI scores of patients with a previous BPPV attack were significantly higher than those of patients with no BPPV-like symptoms; in particular, there was a significant difference in emotional scores. Conclusion Although the patients had no characteristic nystagmus, if they have a BPPV-like history and symptoms, emotional support and periodic follow up are needed. In particular, careful observation should be performed in patients with previous BPPV attack. Keywords: Benign paroxysmal positional vertigo; Anxiety; Depression 중심 단어: 양성돌발성두위현훈, 불안, 우울

Pseudo-spontaneous nystagmus in horizontal semicircular canal canalolithiasis.

Benign paroxysmal positional vertigo (BPPV) involving horizontal semicircular canal (HSCC) is characterized by direction-changing positional nystagmus (DCPN) in a supine roll test, and the occurrence of spontaneous nystagmus in HSCC BPPV has been reported recently. The aim of this study is to investigate the characteristics of pseudo-spontaneous nystagmus (PSN) in patients with HSCC canalolithiasis, and evaluate the effect of the presence of PSN on treatment outcome.Between April 2014 and January 2016, 75 and 59 patients with HSCC canalolithiasis and cupulolithiasis, respectively, were enrolled. Spontaneous and positional nystagmus were examined.PSN was observed in 31 of 75 patients (41%) with HSCC canalolithiasis, and 55 of 59 patients (93%) with HSCC cupulolithiasis. PSN persisted during the period of observation, which was at least 1 minute in all patients with PSN. In HSCC canalolithiasis, direction-reversing nystagmus was observed in 58 patients (25 bilateral and 33 unilateral). Nine of 25 patients with bilateral direction-reversing nystagmus, and 22 of 33 patients with unilateral direction-reversing nystagmus showed PSN. None of 17 patients without direction-reversing nystagmus showed PSN. The direction of PSN corresponded to that of direction-reversing nystagmus in all 22 patients with unilateral direction-reversing nystagmus. The proportion of patients who recovered after 1 session of repositioning maneuver was not significantly different between patients with and without PSN (P = .867).PSN was observed more commonly in HSCC cupulolithiasis than canalolithiasis. The pathophysiologic mechanism underlying PSN can be explained by natural inclination of HSCC and medial to lateral orientation of the HSCC cupular axis in cupulolithiasis, and by spontaneous reversal of initial positional nystagmus (direction-reversing nystagmus) generated by short-term adaptation of vestibulo-ocular reflex in canalolithiasis. The presence of PSN in HSCC canalolithiasis may not affect the treatment outcome.

Incidence and Types of Pediatric Nystagmus

To report the incidence, prevalent subtypes, and clinical characteristics of pediatric nystagmus diagnosed over a 30-year period. Retrospective, population-based study. Using the Rochester Epidemiology Project, we reviewed the medical records of all children (<19 years) diagnosed as residents in Olmsted County, Minnesota, with any form of nystagmus from January 1, 1976, through December 31, 2005. Seventy-one children were diagnosed during the 30-year period, yielding an annual incidence of 6.72 per 100,000 younger than 19 years (95% confidence interval [CI], 5.15-8.28) Infantile nystagmus, onset by 6months, comprised 62 (87.3%) of the study patients, corresponding to a birth prevalence of 1 in 821. The median age at diagnosis for the cohort was 12.7months (range, 0days to 18.6 years) and 42 subjects (59.2%) were male. The main types of nystagmus, in declining order, were nystagmus associated with retinal/optic nerve disease in 23 (32.4%), idiopathic or congenital motor nystagmus in 22 (31.0%), manifest latent nystagmus or latent nystagmus in 17 (24.0%), and 2 (2.8%) each associated with Chiari malformation, medication use, tumor of the central nervous system, and no diagnosis. Developmental delay was diagnosed in 31 (43.6%), strabismus in 25 (35.2%), and amblyopia in 10 (14.1%). Eighty percent had 20/40 (or equivalent) or better vision at presentation in at least 1 eye. This study provides population-based data on incidence and clinical characteristics of childhood nystagmus in North America. Idiopathic and nystagmus associated with retinal/optic nerve disease were the most common presentations, with most patients having good vision. Developmental delay, strabismus, and amblyopia were common in this cohort.

The exploration on optimization of two alternatives between roll test and Dix-Hallpike test in benign paroxysmal positional vertigo

Objective: To analyze the objective characteristics of roll test and Dix-Hallpike test in benign paroxysmal positional vertigo(BPPV)patients, discussing the premier solution of positional test. Methods: A total of 230 patients with BPPV, whereas 170 posterior semicircular canal canalithiasis (PSC-Can) BPPV and 60 horizontal semicircular canal canalithiasis (HSC-Can) BPPV were involved respectively. The induced nystagmus in roll test and Dix-Hallpike test was recorded by video nystagmuo graph (VNG), and the direction, intensity and time characteristics of nystagmus were compared in various BPPV.SPSS19.0 software was used for statistical analysis. Results: Vertically upward nystagmus was induced by hanging in 170 PSC-Can Dix-Hallpike test, and the nystagmus reversed and turned weaker when the subjects came to sit. The intensity of nystagmus at turning to lesion side by hanging and sitting were (30.3±14.1)°/s and (12.6±7.5)°/s respectively, the difference was statistically significant (t=20.153, P<0.05). However, no nystagmus was induced in PSC-Can roll test. Horizontal nystagmus in the same direction with turning was induced in 60 HSC-Can roll test. The intensity of nystagmus at turning to lesion side and normal side was (42.0±18.0)°/s and (20.3±8.7)°/s respectively, the difference was statistically significant (t=12.731, P<0.05). Furthermore, horizontal nystagmus in the same direction with turning was induced in 57 HSC-Can Dix-Hallpike. The coherence was 95% with the results of roll test. Conclusions: Dix-Hallpike test can not only be used to diagnose PSC-Can, but also induce nystagmus in HSC-Can effectively. Whereas the roll test only show significance in diagnosing HSC-Can. To avoid uncomfortable stimulation to patients as much as possible, we suggest to use Dix-Hallpike test at first, and to judge whether using roll test based on the result of the horizontal nystagmus.

The Effect of Gaze Angle on Visual Acuity in Infantile Nystagmus.

Most individuals with infantile nystagmus (IN) have an idiosyncratic gaze angle at which their nystagmus intensity is minimized. Some adopt an abnormal head posture to use this "null zone," and it has therefore long been assumed that this provides people with nystagmus with improved visual acuity (VA). However, recent studies suggest that improving the nystagmus waveform could have little, if any, influence on VA; that is, VA is fundamentally limited in IN. Here, we examined the impact of the null zone on VA. Visual acuity was measured in eight adults with IN using a psychophysical staircase procedure with reversals at three horizontal gaze angles, including the null zone. As expected, changes in gaze angle affected nystagmus amplitude, frequency, foveation duration, and variability of intercycle foveation position. Across participants, each parameter (except frequency) was significantly correlated with VA. Within any given individual, there was a small but significant improvement in VA (0.08 logMAR) at the null zone as compared with the other gaze angles tested. Despite this, no change in any of the nystagmus waveform parameters was significantly associated with changes in VA within individuals. A strong relationship between VA and nystagmus characteristics exists between individuals with IN. Although significant, the improvement in VA observed within individuals at the null zone is much smaller than might be expected from the occasionally large variations in intensity and foveation dynamics (and anecdotal patient reports of improved vision), suggesting that improvement of other aspects of visual performance may also encourage use of the null zone.

Nystagmus at the Onset of Vertiginous Attack in Ménière's Disease.

To clarify the direction and characteristics of nystagmus at the onset of a vertiginous attack in Ménière's disease. Two patients with Ménière's disease, whose nystagmus at the onset of a vertiginous attack was recorded using electronystagmography. Diagnostic. Electronystagmographic recordings of nystagmus. In both patients, nystagmus was directed toward the affected side over the entire course of the vertiginous attack. One patient experienced a severe sensation of vertigo and exhibited strong nystagmus from the onset of the attack. The other patient reported a mild sensation of vertigo, which was accompanied by intermittent nystagmus. Vertiginous attacks in Ménière's disease are accompanied by irritative nystagmus. The intensity and characteristics (e.g., continuous or intermittent expression) of the nystagmus may be associated with pathophysiological severity.

The new method for the treatment of relative amblyopia in the patients presenting with optical nystagmus

Aim. The objective of the present study was to develop the method for the pleoptical treatment of relative amblyopia in the children presenting with optical nystagmus with the use of sinoptophore under conditions of nystagmus blockade. The secondary objective was to evaluate the effectiveness of the proposed method. Materials and methods. The newly developed technique for the pleoptical treatment of relative amblyopia consisted of the blockade of nystagmus by conversion effort and the application of the light pulses to the central fovea of the retina under control of bifoveal fusion. Results. The proposed method was employed to treat 21 patients presenting with optical nystagmus and relative amblyopia at the age varying from 5 to 10 years. In 18 children, the changes in the parameters of nystagmus were evaluated from its amplitude and fixation area density on the retina by means of microperimetry using the NIDEK Microperimeter-MP1 apparatus. The study revealed the tendency toward the improvement of binocular visual acuity, both corrected and uncorrected (by 0.14±0.09 and 0.12±0.07 on the average, respectively), and of the absolute accommodation volume (by 2.88±1.9 diopters). The inverse relationship between the motor parameters of nystagmus and visual acuity was documented. Conclusion. The proposed new method for the pleoptical treatment of relative amblyopia consists of blockade of nystagmus by conversion effort and the delivery of the light pulses to the central fovea of the retina in both eyes under control of bifoveal fusion on sinoptofphore. The method allowed to improve both the functional (enhanced visual acuity) and motor (amplitude and fixation area density) characteristics of nystagmus.

Diagnostic criteria of barotraumatic perilymph fistula based on clinical manifestations

Conclusions: Patients with sudden hearing loss and dizziness after barotrauma should be suspected of barotraumatic perilymph fistula (PLF). Early surgical repair of PLF showed better hearing outcomes. Therefore, diagnostic criteria should help surgical indications of barotraumatic PLF.Objectives: The aim of this study was to establish diagnostic criteria for barotraumatic PLF.Methods: Twenty-four patients (26 ears) underwent surgery on suspicion of barotraumatic PLF. The causes of barotrauma and clinical symptoms were analyzed by surgical findings. Diagnostic criteria of PLF were proposed according to its clinical manifestations.Results: Definite PLF (17 subjects) was confirmed by any evidence of perilymph leak through oval and round windows. For the other seven subjects (probable PLF), even though there was no evidence of perilymph leak, their clinical manifestations were similar to definite PLF. High frequency hearing loss occurred as an early symptom after barotrauma. Positional dizziness occurred a few hours after auditory symptoms (67%). Positional nystagmus was observed in 10 cases. The characteristics of positional nystagmus were multi-directional, longer in duration, smaller in amplitude, no reversibility, and no response to repositioning maneuver. Regarding the surgical outcomes, hearing was significantly improved in the early repaired PFL group, and dizziness was improved in 96% of patients.

Perceptual Learning in Children With Infantile Nystagmus: Effects on 2D Oculomotor Behavior.

To determine changes in oculomotor behavior after 10 sessions of perceptual learning on a letter discrimination task in children with infantile nystagmus (IN). Children with IN (18 children with idiopathic IN and 18 with oculocutaneous albinism accompanied by IN) aged 6 to 11 years were divided into two training groups matched on diagnosis: an uncrowded training group (n = 18) and a crowded training group (n = 18). Target letters always appeared briefly (500 ms) at an eccentric location, forcing subjects to quickly redirect their gaze. Training occurred twice per week for 5 consecutive weeks (3500 trials total). Norm data and test-retest values were collected from children with normal vision (n = 11). Outcome measures were: nystagmus characteristics (amplitude, frequency, intensity, and the expanded nystagmus acuity function); fixation stability (the bivariate contour ellipse area and foveation time); and saccadic eye movements (latencies and accuracy) made during a simple saccade task and a crowded letter-identification task. After training, saccadic responses of children with IN improved on the saccade task (latencies decreased by 14 ± 4 ms and gains increased by 0.03 ± 0.01), but not on the crowded letter task. There were also no training-induced changes in nystagmus characteristics and fixation stability. Although children with normal vision had shorter latencies in the saccade task (47 ± 14 ms at baseline), test-retest changes in their saccade gains and latencies were almost equal to the training effects observed in children with IN. Our results suggest that the improvement in visual performance after perceptual learning in children with IN is primarily due to improved sensory processing rather than improved two-dimensional oculomotor behavior.

The role of MR imaging in investigating isolated pediatric nystagmus.

The use of MRI in isolated pediatric nystagmus remains a gray area in clinical management. Many clinicians prefer to order an MRI to rule out intracranial pathology despite the lack of clinically significant findings in most cases. To assess the yield of MR imaging in isolated pediatric nystagmus and define a management algorithm to minimize avoidable MRI referrals and streamline MRI protocols. We reviewed the charts of 148 children who underwent neuro MRI for isolated nystagmus between January 2008 and September 2014. We noted nystagmus onset and clinical characteristics and compared them with the MRI features and visual electrophysiology results. We included 85 boys and 63 girls (total 148, average age at MRI 4.24 ± 4.19years). Twenty-three (15.5%) children had abnormal intracranial findings on MRI including abnormal signal lesions (4.1%; n=6), Chiari I malformations (3.4%; n=5) and optic pathway glioma (2.0%; n=3). The time of onset of nystagmus was not associated with an abnormal MRI (P=0.2). Seventy children underwent visual electrophysiology testing but this test could not predict abnormality at MRI, either (P=0.12). Among children with isolated nystagmus, 15.5% had abnormalities on neuroimaging. Neither clinical characteristics of nystagmus nor the visual electrophysiology results allowed prediction of intracranial pathology. We were unable to formulate a management algorithm for the optimal sequence of investigations (MRI preceding visual electrophysiology or vice versa), but we discuss the use of gadolinium contrast agent and orbital sequences in isolated pediatric nystagmus.

Incidence and types of pediatric nystagmus

Purpose To report the incidence, prevalent subtypes, and clinical characteristics of pediatric nystagmus diagnosed over a 30-year period. Design Retrospective, population-based study. Methods Using the Rochester Epidemiology Project, we reviewed the medical records of all children ( Results Seventy-one children were diagnosed during the 30-year period, yielding an annual incidence of 6.72 per 100,000 younger than 19 years (95% confidence interval [CI], 5.15–8.28) Infantile nystagmus, onset by 6 months, comprised 62 (87.3%) of the study patients, corresponding to a birth prevalence of 1 in 821. The median age at diagnosis for the cohort was 12.7 months (range, 0 days to 18.6 years) and 42 subjects (59.2%) were male. The main types of nystagmus, in declining order, were nystagmus associated with retinal/optic nerve disease in 23 (32.4%), idiopathic or congenital motor nystagmus in 22 (31.0%), manifest latent nystagmus or latent nystagmus in 17 (24.0%), and 2 (2.8%) each associated with Chiari malformation, medication use, tumor of the central nervous system, and no diagnosis. Developmental delay was diagnosed in 31 (43.6%), strabismus in 25 (35.2%), and amblyopia in 10 (14.1%). Eighty percent had 20/40 (or equivalent) or better vision at presentation in at least 1 eye. Conclusions This study provides population-based data on incidence and clinical characteristics of childhood nystagmus in North America. Idiopathic and nystagmus associated with retinal/optic nerve disease were the most common presentations, with most patients having good vision. Developmental delay, strabismus, and amblyopia were common in this cohort.

Spontaneous, headshaking, and positional nystagmus in post-lateral medullary infarction dizziness

Background and purposeLateral medullary infarction (LMI) sometimes causes long-lasting dizziness. However, the characteristics of nystagmus in patients with post-LMI dizziness are unknown. We undertook a prospective, comparative study of nystagmus in patients with and without post-LMI dizziness to determine the characteristic pattern of nystagmus of chronic post-LMI dizziness. MethodsWe evaluated and compared nystagmus under spontaneous, head-shaking, and positional testing conditions in 12 patients with post-LMI dizziness and in 6 patients without post-LMI dizziness. ResultsIn the dizziness group, contralateral spontaneous nystagmus, ipsilateral head-shaking nystagmus, and horizontal direction-changing geotropic positional nystagmus were observed in patients in whom the LMI had occurred <60days previously (subacute period). In patients with dizziness in whom the LMI had occurred >90days previously (chronic period), the nystagmus was ipsilateral under all conditions. In the non-dizziness group, ipsilateral nystagmus was observed in 1 of the 2 subacute patients only after head-shaking and in 1 of the 4 chronic patients only during positional testing. ConclusionsIpsilateral nystagmus observed under all spontaneous, head-shaking, and positional testing conditions characterizes chronic post-LMI dizziness.

Direction-reversing Nystagmus in Horizontal and Posterior Semicircular Canal Canalolithiasis.

To investigate the incidence and characteristics of direction-reversing nystagmus in patients with horizontal (HSCC) and posterior semicircular canal (PSCC) canalolithiasis, and evaluate the effect of direction-reversing nystagmus on the treatment outcome. A retrospective study. Between March 2014 and September 2015, 63 and 92 consecutive patients with HSCC and PSCC canalolithiasis, respectively, were enrolled. Positional nystagmus characteristics were examined using video-nystagmography. In HSCC canalolithiasis, direction-reversing nystagmus was observed in 73% of patients (46 of 63), of which 19 cases were bilateral and 27 unilateral. In patients with bilateral reversal, maximal slow-phase velocity (mSPV) was significantly greater when the head turned to the lesioned side than to the healthy side in both the first and second phase. In all patients with unilateral reversal, direction-reversing nystagmus always occurred in the side of stronger initial nystagmus in a supine roll test. The mean mSPV of first phase nystagmus was significantly greater on the side with reversal than without (p < 0.001). The duration of second-phase nystagmus exceeded 60 seconds in all patients with reversal. Although not statistically significant (p = 0.059), patients presenting with direction-reversing nystagmus required more repositioning maneuver sessions. In contrast to HSCC canalolithiasis, only 4% of patients (4 of 92) with PSCC canalolithiasis exhibited spontaneous reversal of initial nystagmus. The incidence of direction-reversing nystagmus was higher in HSCC canalolithiasis than in PSCC canalolithiasis, and second-phase (direction-reversing) nystagmus in HSCC canalolithiasis has a prolonged duration. Short-term adaptation of the vestibulo-ocular reflex may be responsible for the development of direction-reversing nystagmus.

Sudden sensorineural hearing loss with positional vertigo: Initial findings of positional nystagmus and hearing outcomes

Objectives: To investigate the initial findings of positional nystagmus in patients with sudden sensorineural hearing loss (SSNHL) and positional vertigo, and to compare hearing improvement among patients with different types of positional nystagmus. Design: The characteristics of positional nystagmus upon initial examination were analysed, and the initial mean pure-tone audiometry (PTA) threshold was compared with that at three months after treatment. Study sample: Forty-four SSNHL patients with concomitant positional vertigo were included. Results: Positional nystagmus was classified into five subgroups; persistent geotropic direction-changing positional nystagmus (DCPN) in head-roll test (HRT) and negative Dix-Hallpike test (DHT), persistent apogeotropic DCPN in HRT and negative DHT, positive DHT and negative HRT, persistent geotropic DCPN in HRT and positive DHT, and persistent apogeotropic DCPN in HRT and positive DHT. PTA threshold improvement was significantly greater in SSNHL patients with negative DHT than with positive DHT (p = 0.027). Conclusions: When geotropic DCPN was elicited by HRT, the nystagmus was persistent, which suggests that alteration of specific gravity of the endolymph, rather than the lateral canal canalolithiasis, may be a cause of this characteristic positional nystagmus. Positive DTH may be a prognostic factor for worse hearing recovery among patients with SSNHL and positional vertigo.

Clinical evaluation of acute phase nystagmus associated with cerebellar lesions

To determine the characteristics of acute phase nystagmus in patients with cerebellar lesions, and to identify a useful indicator for differentiating central lesions from peripheral lesions. Acute phase nystagmus and the appearance of neurological symptoms were retrospectively investigated in 11 patients with cerebellar stroke. At the initial visit, there were no patients with vertical nystagmus, direction-changing gaze evoked nystagmus or pure rotatory nystagmus. There were four cases with no nystagmus and seven cases with horizontal nystagmus at the initial visit. There were no neurological symptoms, except for vertigo and hearing loss, in any cases at the initial visit. The direction and type of nystagmus changed with time, and neurological symptoms other than vertigo appeared subsequently to admission. It is important to observe the changes in nystagmus and other neurological findings for the differential diagnosis of central lesions.

Necessity of repeated roll test in horizontal semicircular canalithasis positioned diagnosis

To investigate the influence of repeated roll test in horizontal semicircular canalithasis(HSC-Can) positioned diagnosis, so as to investigate the cecessity of repeated roll test. The patients with a chief complaint of positional vertigo accepted two consecutive cycles roll test, the evoked nystagmus characteristics of each cycle recorded by video-nystagmuograph(VNG), whose direction, intensity, time and other parameters characteristics were analyzed in 51 HSC-Can. Horizontal nystagmus in the same direction with turning were induced in HSC-Can roll test. In 51 HSC-Can, roll test cycle 1 and cycle 2 induced nystagmus same strength side in 26 cases(51.0%), of which 19 cases with stronger nystagmus intensity in cycle 2, another 7 cases were weaker; the opposite strength side of the two loops induced nystagmus, and cycle 1 evoked nystagmus intensity were weaker than cycle 2, based on cycle 2 results determined HSC-Can affected side in 25 cases (49.0%). Lesion and normal side in cycle 1 induced nystagmus duration (x±s, the same below) were (13.4±11.5)s and (14.1±9.9)s, respectively intensity (18.1±22.4)°/s and (13.0±12.0)°/s; as in cycle 2 induced nystagmus duration was (20.7±10.2)s and (18.0±12.0)s, strength respectively(40.4±28.0)°/s and (15.6 ±11.2)°/s. Cycle 2 ipsilateral rotor position evoked nystagmus showed longer duration and stronger intensity than cycle 1. Between two cycle induced ipsilateral nystagmus duration, intensity differences were statistically significant (t values were -4.233 and -5.154, P=0.000). 51 HSC-Can patients, 44 patients selected repositioning maneuver, after 1-2 times of maneuver, 41 cases (93.2%) showed complete resolution of symptoms, all cases's symptoms were improved; other 7 patients selected medication only. The proposed suspicious HSC-Can patients should receive at least two cycles roll test, and mainly in the second cycle could determine the location of the responsible semicircular canals.

Prevalence and Characteristics of Positional Nystagmus in Normal Subjects.

In clinical practice, patients are often referred due to a finding of positional nystagmus that does not always appear to correlate with clinical symptoms of benign paroxysmal positional vertigo. To know when to consider nystagmus to be of clinical relevance, it is necessary to know the prevalence and characteristics of positional nystagmus in a healthy population. Case series of 75 healthy subjects. Two tertiary referral centers in Norway. Seventy-five adult subjects aged 40 ± 13 years (mean ± SD; range, 21-87) without a history of vertigo or balance disorder were included from 2013 to 2015. The subjects underwent 6 different standardized positional tests in a repositioning chair. Videonystagmography was used to record eye movements. Of 1350 recordings, 1329 were included and analyzed. Positional nystagmus was detected in 88% of the subjects. The most common finding was nystagmus in the Dix-Hallpike position, which occurred in 55% of the subjects. The 95th percentile of the maximum slow-phase velocity for each subject was found to be 5.06° per second (n = 54) in the horizontal plane and 6.48° per second (n = 48) in the vertical plane. Positional nystagmus is a common finding in normal subjects and occurred in 88% of the healthy subjects in the present study. Horizontal direction-changing apogeotropic or geotropic nystagmus may occur in asymptomatic subjects. However, nystagmus that is of the paroxysmal type or has a slow-phase velocity greater than approximately 5° per second in the horizontal plane or 6.5° per second in the vertical plane should be considered outside the 95th percentile.

Clinical Characteristics of Spontaneous Downbeat Nystagmus in Koreans: Analysis of 218 Cases

Background: Downbeat nystagmus is the most-common type of central nystagmus. However, no published study has attempted to analyze the etiology and clinical features of downbeat nystagmus in a large sample of Korean patients. Methods: We analyzed the demographic and clinical features of spontaneou s downbeat nystagmus in 218 Korean patients who had been evaluated at the Dizziness Clinic of Seoul National University Bundang Hospital from 2003 to 2014. Results: All patients were aged from 15 to 92 years (mean±SD: 58.7±18.0 years), and they included 117 (53.7%) men. Underlying causes were found in 162 patients (74.3%, secondary group), while no etiology was identified in the remaining patients (idiopathic group). The age and sex distributions did not differ between the idiopathic and secondary groups. The underlying etiology included hereditary disorders (n＝48, 22.0%), vascular diseases (n＝46, 21.1%), and inflammatory diseases (n＝19, 8.7%). Infarctions (n＝34, 15.6%) and episodic ataxia (n＝32, 14.7%) were the most-frequent underlying disorders. The most-common site of lesions identified by MRI was the cerebellum (68.9%), followed by the brainstem (28.6%). Among the 74 patients with lesions confirmed by MRI, 25 (33.7%) showed an isolated cerebellar involvement, while 35 (47.6%) had lesions in multiple areas. Conclusions: This study extends the clinical features of spontaneous downbeat nystagmus to Korean patients. Cerebellum is the most-common lesion site, which is consistent with the results of previous studies. The prevalence of Arnold-Chiari malformation is relatively low, which may be a di stinct finding relative to those of previous studies involving other ethnic populations. J Korean Neurol Assoc 34(1):27-32, 2016

Positional Nystagmus in Patients Evaluated for Dizziness and Imbalance

There is variability in the literature regarding the presence of positional nystagmus in healthy participants with reportedly normal vestibular and central nervous system function. This ranges from 7.5% to 88% and raises an important clinical question. If 88% of healthy participants have positional nystagmus then how is the clinician to interpret the presence of positional nystagmus in a patient presenting with dizziness and/or disequilibrium? The primary purpose of this investigation was to examine the prevalence and characteristics of positional nystagmus in patients evaluated specifically for dizziness and imbalance. Data was collected using retrospective chart review. 200 charts were randomly selected from all patients seen for evaluation of dizziness and imbalance over a period of eight months. Clinicians independently reviewed the data from positional testing for each chart. Nystagmus was present if there was a clear slow and fast phase component and there were three beats in a 10 s time window. Nystagmus direction and intensity data were collected. Results indicate positional nystagmus is present in 10.5% to 21% of patients evaluated for dizziness and imbalance. Use of liberal criteria for determining presence of positional nystagmus (i.e., 3 beats in 20 sec) may account for higher prevalence rates across other studies.

How Were Eye Movements Recorded Before Yarbus?

Alfred Yarbus introduced a new dimension of precision in recording how the eyes moved, either when attempts were made to keep them stationary or when scanning pictures. Movements of the eyes had been remarked upon for millennia, but recording how they move is a more recent preoccupation. Emphasis was initially placed on abnormalities of oculomotor function (like strabismus) before normal features were considered. The interest was in where the eyes moved to rather than determining how they got there. The most venerable technique for examining ocular stability involved comparing the relative motion between an afterimage and a real image. In the late 18th century, Wells compared afterimages generated before body rotation with real images observed following it when dizzy; he described both lateral and torsional nystagmus, thereby demonstrating the directional discontinuities in eye velocities. At around the same time Erasmus Darwin used afterimages as a means of demonstrating ocular instability when attempting to fixate steadily. However, the overriding concern in the 19th century was with eye position rather than eye movements. Thus, the characteristics of nystagmus were recorded before those of saccades and fixations. Eye movements during reading were described by Hering and by Lamare (working in Javal's laboratory) in 1879; both used similar techniques of listening (with tubes placed over the eyelids) to the sounds made during contractions of the extraocular muscles. Photographic records of eye movements during reading were made by Dodge early in the 20th century, and this stimulated research using a wider array of patterns. Eye movements over pictures were examined by Stratton and later by Buswell, who drew attention to the effects of instructions on the pattern of eye movements. In midcentury, attention shifted back to the stability of the eyes during fixation, with the emphasis on involuntary movements. The suction cap methods developed by Yarbus were applied with some success to recording the perceptual effects of retinal image stabilization. It is an historical irony that the accuracy of image stabilization with contact lenses was assessed by comparison with the oldest method for examining eye movements--afterimages.