Identification of Stroke and TIA in Patients With Acute Dizziness, Vertigo or Imbalance in Emergency Departments of Primary Care Hospitals: Early Experiences With a Network-Based Telemedical Approach.

Background: Acute dizziness, vertigo, and imbalance are frequent and difficult to interpret symptoms in the emergency department (ED). Primary care hospitals often lack the expertise to identify stroke or TIA as underlying causes. A telemedical approach based on telestroke networks may offer adequate diagnostics and treatment. Aim: The aim of this study is to evaluate the accuracy of a novel ED algorithm in differentiating between peripheral and central vestibular causes. Methods: Within the Telemedical Project for Integrative Stroke Care (TEMPiS), a telemedical application including a videooculography (VOG) system was introduced in 2018 in 19 primary care spoke hospitals. An ED triage algorithm was established for all patients with acute dizziness, vertigo, or imbalance of unknown cause (ADVIUC) as a leading complaint. In three predefined months, all ADVIUC cases were prospectively registered and discharge letters analyzed. Accuracy of the ED triage algorithm in differentiation between central and peripheral vestibular cases was analyzed by comparison of ED diagnoses to final discharge diagnoses. The rate of missed strokes was calculated in relation to all cases with a suitable brain imaging. Acceptance of teleconsultants and physicians in spoke hospitals was assessed by surveys. Results: A total number of 388 ADVIUC cases were collected, with a median of 12 cases per months and hospital (IQR 8-14.5). The most frequent hospital discharge diagnoses are vestibular neuritis (22%), stroke/TIA (18%), benign paroxysmal positioning vertigo (18%), and dizziness due to internal medicine causes (15%). Detection of a central vestibular cause by the ED triage algorithm has a high sensitivity (98.6%), albeit poor specificity (45.9%). One stroke out of 32 verified by brain scan was missed (3.1%). User satisfaction, helpfulness of the project, improvement of care, personal competence, and satisfaction about handling of the VOG systems were rated consistently positive. Discussion: The concept shows good acceptance for a telemedical and network-based approach to manage ADVIUC cases in the ED of primary care hospitals. Identification of stroke cases is accurate, while specificity needs further improvement. The concept could be a major step toward a broadly available state of the art diagnostics and therapy for patients with ADVIUC in primary care hospitals.

Feasibility of Telemedical HINTS (Head Impulse-Nystagmus-Test of Skew) Evaluation in Patients With Acute Dizziness or Vertigo in the Emergency Department of Primary Care Hospitals.

BACKGROUND: Acute dizziness, vertigo and imbalance are common symptoms in emergency departments. Stroke needs to be distinguished from vestibular diseases. A battery of three clinical bedside tests (HINTS: Head Impulse Test, Nystagmus, Test of Skew) has been shown to detect stroke as underlying cause with high reliability, but implementation is challenging in primary care hospitals. Aim of this study is to prove the feasibility of a telemedical HINTS examination via a remotely controlled videooculography (VOG) system. METHODS: The existing video system of our telestroke network TEMPiS (Telemedic Project for Integrative Stroke Care) was expanded through a VOG system. This feature enables the remote teleneurologist to assess a telemedical HINTS examination based on inspection of eye movements and quantitative video head impulse test (vHIT) evaluation. ED doctors in 11 spoke hospitals were trained in performing vHIT, nystagmus detection and alternating cover test. Patients with first time acute dizziness, vertigo or imbalance, whether ongoing or resolved, presented to the teleneurologist were included in the analysis, as long as no focal neurological deficit according to the standard teleneurological examination or obvious internal medicine cause was present and a fully trained team was available. Primary outcome was defined as the feasibility of the telemedical HINTS examination. RESULTS: From 01.06.2019 to 31.03.2020, 81 consecutive patients were included. In 72 (88.9%) cases the telemedical HINTS examination was performed. The complete telemedical HINTS examination was feasible in 46 cases (63.9%), nystagmus detection in all cases (100%) and alternating covert test in 70 cases (97.2%). The vHIT was recorded and interpretable in 47 cases (65.3%). Results of the examination with the VOG system yielded clear results in 21 cases (45.7%) with 14 central and 7 peripheral lesions. The main reason for incomplete examination was the insufficient generation of head impulses. CONCLUSION: In our analysis the telemedical HINTS examination within a telestroke network was feasible in two thirds of the patients. This offers the opportunity to improve specific diagnostics and therapy for patients with acute dizziness and vertigo even in primary care hospitals. Improved training for spoke hospital staff is needed to further increase the feasibility of vHIT.

Age-related Refixating Saccades in the Three-Dimensional Video-Head-Impulse Test: Source and Dissociation From Unilateral Vestibular Failure.

OBJECTIVE: To examine "refixating saccades" in the three-dimensional video-head impulse test (vHIT) depending on the age and compare them to refixating saccades in pathological vHIT. DESIGN: Retrospective database study. SETTING: County hospital, specialized vertigo center. PATIENTS: Eight hundred ninety-nine patients without a peripheral vestibular hypofunction were tested with the three-dimensional vHIT and compared with 135 patients with unilateral vestibular hypofunction (UVF). MAIN OUTCOME MEASURES: Occurrence and peak velocity of refixating saccades (covert and overt) during the video-head-impulse test (vHIT) in three age groups (0-30, 30-60, and 60-100 yr) and in UVF. RESULTS: Overt saccade frequency of refixating saccades increased with increasing age, especially in the horizontal and posterior vHIT. Saccades were mostly directed opposite to the head movement. The aging effect was not explained by the VOR-gain decrease. Refixating saccades in normal vHIT were less frequent and slower than in UVF. CONCLUSION: We conclude that refixating saccades increase with higher age and could be differentiated from those in UVF by frequency and peak velocity. Saccades are not caused by a deficient VOR but might be caused by a deficient suppression of saccades to novel targets.

Prediction of Short-Term Outcome in Acute Superior Vestibular Nerve Failure: Three-Dimensional Video-Head-Impulse Test and Caloric Irrigation.

This retrospective study examines acute unilateral vestibular failure (up to seven days after onset) with modern vestibular testing (caloric irrigation and video-head-impulse test, vHIT) in 54 patients in order to test if the short-term outcome of the patients depends on the lesion pattern defined by the two tests. Patients were grouped according to a pathological unilateral caloric weakness without a pathological vHIT: group I; additional a pathological vHIT of the lateral semicircular canal (SCC): group II; and an additional pathological vHIT of the anterior SCC: group III. Patients with involvement of the posterior SCC were less frequent and not included in the analysis. Basic parameters, such as age of the subjects, days after symptom onset, gender, side of the lesion, treatment, and dizziness handicap inventory, were not different in groups I to III. The frequency of pathological clinical findings and pathological quantified measurements increased from groups I to III. The outcome parameter "days spent in the hospital" was significantly higher in group III compared to group I. The analysis shows that differential vestibular testing predicts short-term outcome of the patients and might be in future important to treat and coach patients with vestibular failure.

Economic management of vertigo/dizziness disease in a county hospital: video-head-impulse test vs. caloric irrigation.

The video-head-impulse test (vHIT) is an important test for examining unilateral vestibular hypofunction. Alternatively, one can test for vestibular hypofunction with the caloric irrigation test. Various studies have shown that both tests may not always identify vestibular hypofunction; instead, the results of the tests might be contradictory. This retrospective study reproduces those finding in a much larger group of patients at a county hospital. 1063 patients were examined with the vHIT and bithermal caloric irrigation on the same day and analyzed with respect to side differences. Of those patients 13.3% had pathological vHIT and a caloric irrigation test, 4.6% a pathological vHIT only and 24.1% a pathologic caloric test only. As both tests might be necessary, we calculated the optimal sequence of the two examinations based on savings in time for the different disease groups. Especially in vestibular failure using the vHIT first and only applying the caloric irrigation in case of an unremarkable vHIT saves time and optimizes the diagnostic work up. In contrast, in Menière's disease and vestibular migraine testing caloric irrigation first might be more efficient.

Relation of video-head-impulse test and caloric irrigation: a study on the recovery in unilateral vestibular neuritis.

The head-impulse test (HIT) is an important test for examining unilateral vestibular hypofunction. The new video-head-impulse test (vHIT) is more sensitive and specific than the clinical bedside-head-impulse test. Alternatively, one can test for vestibular hypofunction with the caloric irrigation test. Various studies have shown that both tests may not always identify vestibular hypofunction; instead, the results of the tests might be contradictory. To further explore the question, of whether vHIT and caloric irrigation test the same part of the angular horizontal vestibulo-ocular reflex (VOR), we examined patients with unilateral vestibular neuritis at different points in time. The tonic vestibular imbalance (e.g., subjective-visual-vertical, ocular torsion and spontaneous nystagmus) and dynamic dysfunction of VOR (vHIT and bithermal caloric irrigation) were measured and quantified. While parameters of the tonic vestibular imbalance were well described by single exponential decay functions, dynamic parameters were less well defined. Therefore, to better compare the time course of pairs of two different parameters, we used a linear regression analysis. No linear correlation was found in the group and individually for the gain asymmetry and the ipsilesional gain of the vHIT with the unilateral weakness of the bithermal caloric irrigation tests. Linear correlation was found for most parameters of tonic vestibular imbalance. These findings are further evidence that vHIT and caloric irrigation test different parts of the angular VOR.

Caloric test and video-head-impulse: a study of vertigo/dizziness patients in a community hospital.

The head-impulse test (HIT) is an important test for examining unilateral vestibular hypofunction. The new video-head-impulse test (vHIT) is more sensitive and specific than the clinical bedside-head-impulse test (bHIT). Alternatively, one can test for vestibular hypofunction with the caloric irrigation test. Various studies showed that both tests may not always identify vestibular hypofunction; instead, the results of the tests might be contradictory. To evaluate the diagnostic value of these tests, we routinely measured patients exhibiting vertigo or dizziness at our community hospital with bithermal caloric irrigation, the bHIT and the vHIT. Only those patients (n = 172) with a pathological caloric irrigation test of more than 25 % unilateral weakness in the Jongkee's formula were included. Out of these patients, 41 % had a pathologic vHIT. Among the subgroup with acute symptoms (symptom onset within 5 days), 63 % had a pathological video-head-impulse, whereas only 33 % of the non-acute group (symptom onset more than 5 days) tested pathological. A pathological HIT depended on the disease stage, the amount of unilateral weakness in caloric examination and on the test itself.

Evidence from vergence eye movements that disparities defined by luminance and contrast are sensed by independent mechanisms.

We recorded the initial disparity vergence responses (DVRs) elicited by 1-D sinusoidal gratings differing in phase at the two eyes by 1/4 wavelength and defined by luminance modulation (LM) or contrast modulation (CM) of dynamic binary noise. Both LM and CM stimuli elicited DVRs, but those to CM had longer latency (on average by ∼20 ms). DVRs showed sigmoidal dependence on depth of modulation, with higher thresholds for CM than for LM. With both LM and CM stimuli, fixing the modulation at one eye well above threshold rendered the DVR hypersensitive to low-level modulation at the other eye (dichoptic facilitation). Disparities defined by LM at one eye and CM at the other generated weak DVRs in the "wrong" direction, consistent with mediation entirely by distortion products associated with the CM stimulus. These (reversed) DVRs could be nulled by adding LM to the CM stimulus (in phase), and the greater the depth of the CM, the greater the added LM required for nulling, exactly as predicted by a simple compressive non-linearity. We conclude that disparities defined by LM and by CM are sensed by independent cortical mechanisms, at least for the purposes of generating short-latency vergence eye movements to disparity steps.

Structural changes in the human brain following vestibular neuritis indicate central vestibular compensation.

Vestibular neuritis (VN) is a sudden unilateral vestibular failure (UVF) with a variable course. Caloric hyporesponsiveness often persists, and it is largely unknown why patients with the same degree of hyporesponsiveness show different functional recovery. As the peripheral vestibular deficit alone does not seem to determine functional recovery, it was the aim of this study to elucidate whether structural (morphological) brain changes (1) contribute to central vestibular compensation, and (2) account for the variability of clinical recovery in VN. Structural global gray-matter volume (GMV) changes in 15 VN patients were compared with age-matched controls. Morphometric changes in multisensory vestibular cortices, which may be related to functional disability scores, were hypothesized. Patients were examined with neuro-otological tests and clinical scores to assess vestibular disability. Using voxel-based morphometry (VBM, SPM2), categorical comparison revealed GMV increase in patients' multisensory vestibular cortices [insula, inferior parietal lobe (IPL), superior temporal gyrus (STG)], cerebellum, and motion-sensitive areas in the middle temporal area (MT). GMV decrease was found in the midline pontomedullary junction. Simple regression analysis revealed (1) GMV increase in insula and retroinsular vestibular cortex and STG with improving clinically assessed vestibular deficits, and (2) GMV increase in insula vestibular cortex and STG with improving self-assessed vestibular impairment. For the first time, these data suggest structural cortical plasticity in multisensory vestibular-cortex areas in VN that are related to clinical vestibular function and vertigo. As increase of GMV was related to an improvement of vestibular function, structural alterations may be related to central vestibular compensation.

Why do patients with impaired vergence not show "saccadic" vergence?

Low gain of the smooth-pursuit system causes correcting saccades that are clinically observed as "saccadic pursuit." In contrast, low gain of the vergence system during tracking does not appear to cause "saccadic tracking." To further evaluate whether this clinical observation is caused by a missing interaction of vergence to step and ramp targets, vergence eye movements to step-ramp, step, and ramp targets in 3-dimensional space were tested. Results show that vergence to a step and a ramp stimulus is additive in the step-ramp paradigm, indicating no interaction of both components.

Familial voluntary nystagmus.

PURPOSE: To examine the pathological significance and familial occurrence of voluntary nystagmus. PATIENTS AND METHODS: We examined two families orthoptically as well as with video and search-coil techniques or electronystagmography (ENG). Three members of three generations of the first family and a 9-year-old boy from a second family not related to the first were able to generate a voluntary horizontal nystagmus. RESULTS: The characteristics of the nystagmus of our original patient, his daughter and 8-year-old grandson (1st family) were remarkably similar: duration of 2-5 seconds, amplitudes of 1-4 degrees and frequencies around 15 cycles/second. In the second family, our patient with a congenital esotropia and hyperopia was the only one of his family who could voluntarily produce a nystagmus of about 5 degrees and 10 cycles/second for maximum of 20 seconds. During prolonged reading, the same nystagmus with disturbing oscillopsia developed involuntarily and was not suppressible. We added +0.75 diopters to both lenses of his spectacles to account for the result of our cycloplegic refraction. This stopped the involuntary nystagmus during near fixation. DISCUSSION: To avoid unintentional "bouts" of voluntary nystagmus, a reduction of the convergence impulse by plus-lenses may be effective. The parameters of voluntary nystagmus can be considered family-specific.

Age-related changes of vergence under natural viewing conditions.

Vergence eye movements were recorded with the scleral search-coil system in 32 healthy subjects (ages 19-73 years) to characterize the age-related effects on the dynamic parameters of vergence responses to step (transient components) and ramp or sinusoidal targets (sustained components) under natural viewing conditions. Transient vergence showed an age-related increase in latency and decreases in peak velocity and acceleration in the binocular stimulus condition but not in accommodative vergence. Sustained vergence showed no age-related effect in the binocular condition, but there was an age-related decrease in accommodative vergence steady-state velocity and an increase in latency. Age-related changes of the transient and sustained components were very similar to those reported for saccades and smooth pursuit; they thus might support a distinction between a sustained and transient vergence system. Furthermore, such age-related effects have to be taken into account when assessing eye movement disorders in neurodegenerative and cerebrovascular diseases.

Effect of 3,4-diaminopyridine on the postural control in patients with downbeat nystagmus.

Downbeat nystagmus (DBN) is a common, usually persistent ocular motor sign in vestibulocerebellar midline lesions. Postural imbalance in DBN may increase on lateral gaze when downbeat nystagmus increases. 3,4-Diaminopyridine (3,4-DAP) has been shown to suppress the slow-phase velocity component of downbeat nystagmus and its gravity-dependent component with concomitant improvement of oscillopsia. Because the pharmacological effect is thought to be caused by improvement of the vestibulocerebellar Purkinje cell activity, the effect of 3,4-DAP on the postural control of patients with downbeat nystagmus syndrome was examined. Eye movements were recorded with the video-based Eyelink II system. Postural sway and pathway were assessed by posturography in lateral gaze in the light and on eye closure. Two out of four patients showed an improvement of the area of postural sway by 57% of control (baseline) on eye closure. In contrast, downbeat nystagmus in gaze straight ahead and on lateral gaze did not benefit in these two patients, implying a specific influence of 3,4-DAP on the vestibulocerebellar control of posture. It was concluded that 3,4-DAP may particularly influence the postural performance in patients with downbeat nystagmus.

Effect of blinks on saccades before smooth-pursuit eye-movement initiation.

The effect of blinks on the saccade frequency before the onset of step ramp smooth pursuit was assessed in healthy controls. Blinks elicited before smooth pursuit onset suppressed saccades in contrast to a control and a gap paradigm. The source of blink associated suppression of saccades remains unclear but is probably not caused by visual signals or the omnipause neurons.

Palsy of "fast" and "slow" vergence by pontine lesions.

The role of pontine nuclei in vergence eye movements to "step" targets ("fast" vergence) is unknown. Eye movements were recorded in two patients with unilateral pontine infarctions and in 11 healthy controls. In addition to the deficit of "slow" vergence, "fast" vergence was particularly impaired. However, conjugate saccades did not differ from controls, but smooth pursuit eye movements did. The authors conclude that "fast" vergence palsy is not only caused by midbrain but also upper pontine lesions.

Blink effects on ongoing smooth pursuit eye movements in humans.

Blinks are known to affect eye movements, e.g., saccades, slow and fast vergence, and saccade-vergence interaction, in two ways: by superimposition of blink-associated eye movements and changes of the central premotor activity in the brainstem. The goal of this study was to determine, for the first time, the effects of trigeminal evoked blinks on ongoing smooth pursuit eye movements which could be related to visual sensory or premotor neuronal changes. This was compared to the effect of a target disappearing for 100-300 ms duration during ongoing smooth pursuit (blank paradigm) in order to control for the visual sensory effects of a blink. Eye and blink movements were recorded in eight healthy subjects with the scleral search coil technique. Blink-associated eye movements during the first 50% of the blink duration were non-linearly superimposed on the smooth pursuit eye movements. Immediately after the blink-associated eye movements, the pursuit velocity slowly decreased by an average of 3.2+/-2.1 degrees /s. This decrease was not dependent on the stimulus direction. The pursuit velocity decrease caused by blinks which occluded the pupil more than 50% could be explained mostly by blanking the visual target. However, small blinks that did not occlude the pupil (<10% of lid closure) also decreased smooth pursuit velocity. Thus, this blink effect on pursuit velocity cannot be explained by blink-associated eye movements or by the blink having blanked the visual input. We propose that part of this effect might either be caused by incomplete visual suppression during blinks and/or a change in the activity of omnipause neurons.

Vergence deficits in pontine lesions.

Eye movements were recorded with the search coil system in two patients to determine whether lesions of the pontine nuclei selectively impair vergence to ramp targets (slow vergence) or step targets (fast vergence). Whereas conjugate saccades were not different from healthy control subjects, conjugate smooth pursuit eye movements had a reduced gain in horizontal and vertical directions. Slow convergence and divergence were impaired, whereas fast vergence did not differ from that of control subjects. Pontine nuclei appear to be involved in the slow vergence control.