Testing Navigation in Real Space: Contributions to Understanding the Physiology and Pathology of Human Navigation Control

Successful navigation relies on the flexible and appropriate use of metric representations of space or topological knowledge of the environment. Spatial dimensions (2D vs. 3D), spatial scales (vista-scale vs. large-scale environments) and the abundance of visual landmarks critically affect navigation performance and behavior in healthy human subjects. Virtual reality (VR)-based navigation paradigms in stationary position have given insight into the major navigational strategies, namely egocentric (body-centered) and allocentric (world-centered), and the cerebral control of navigation. However, VR approaches are biased towards optic flow and visual landmark processing. This major limitation can be overcome to some extent by increasingly immersive and realistic VR set-ups (including large-screen projections, eye tracking and use of head-mounted camera systems). However, the highly immersive VR settings are difficult to apply particularly to older subjects and patients with neurological disorders because of cybersickness and difficulties with learning and conducting the tasks. Therefore, a need for the development of novel spatial tasks in real space exists, which allows a synchronous analysis of navigational behavior, strategy, visual explorations and navigation-induced brain activation patterns. This review summarizes recent findings from real space navigation studies in healthy subjects and patients with different cognitive and sensory neurological disorders. Advantages and limitations of real space navigation testing and different VR-based navigation paradigms are discussed in view of potential future applications in clinical neurology

Is There an “Acquired Idiopathic Head-Shaking Nystagmus”?—A Discussion of Mechanisms and Clinical Implications Based on a Case Report

Background: Head-shaking nystagmus (HSN) occurs in both peripheral and central vestibular disorders. In most cases, HSN can be attributed to an asymmetric peripheral vestibular input or a structural lesion mostly in the cerebellum affecting the central velocity storage mechanism. An isolated HSN is very rare. Case Presentation: We report on a young female patient with the clinical picture of recurrent episodes of vertigo, which were induced by fast head movements and were accompanied by a severe right-beating HSN with a long time constant of 60 s. There was no other clinical and instrument-based evidence of peripheral vestibular dysfunction (including video head impulse test, caloric test, vestibular-evoked myogenic potentials) or indication of a structural lesion in the nodulus, uvula or pontomedullary brainstem on fine-slice magnetic resonance imaging. She had no previous history of migraine, hearing deficits, or other focal neurological symptoms. Diagnostic criteria for vestibular paroxysmia, vestibular migraine, benign peripheral paroxysmal vertigo, or any other known vestibular disorders were not fulfilled. Chart review in the database of the German Center for Vertigo and Balance Disorders indicated eight additional patients with a similar clinical phenotype between 2018 and 2022. Conclusion: We propose a clinical entity called acquired idiopathic head shaking nystagmus (aiHSN) as a rare cause of episodic vertigo induced by fast head movements. Nystagmus characteristics suggest a subtle functional pathology of the central velocity storage mechanism in the nodulus and uvula, which is exacerbated during symptomatic episodes

DIZZYNET 2020: basic and clinical vestibular research united

Objective!#!To investigate diagnostic accuracy of a nerve ultrasound (US) protocol that is individualized to a patient's clinical deficits for the differentiation of amyotrophic lateral sclerosis with predominant lower motoneuron disease (ALS/LMND) and multifocal motor neuropathy (MMN).!##!Methods!#!Single-center, prospective, examiner-blinded, diagnostic study in two cohorts. Cohort I (model development): Convenience sample of subjects with ALS/LMND or MMN according to revised El-Escorial or EFNS guidelines. Cohort II (model validation): Consecutively recruited treatment-naïve subjects with suspected diagnosis of ALS/LMND or MMN. Cutoffs for 28 different US values were determined by Receiver Operating Curve (ROC) in cohort I. Area Under The Curve (AUC) of US was compared to nerve conduction studies (NCS). Diagnostic accuracy of US protocols, individualized according to clinical deficits, was compared to former rigid non-individualized protocols and to random examination site selection in cohort II.!##!Results!#!48 patients were recruited. In cohort I (28 patients), US had higher ROC AUCs than NCS, US 0.82 (0.12) (mean (standard deviation)), NCS (compound muscle action potential (CMAP) 0.60 (0.09), p < .001; two-sided t-test). US models based on the nerve innervating the clinically most affected muscles had higher correct classification rates (CCRs, 93%) in cohort II than former rigid protocols (85% and 80%), or models with random measurement site selection (66% and 80%).!##!Conclusions!#!Clinically guided US protocols for differentiation of ALS/LMND from MMN increase diagnostic accuracy when compared to clinically unguided protocols. They also require less measurements sites to achieve this accuracy

Telling friend from foe in emergency vertigo and dizziness: does season and daytime of presentation help in the differential diagnosis?

Distinguishing between serious (e.g., stroke) and benign (e.g., benign paroxysmal positional vertigo, BPPV) disorders remains challenging in emergency consultations for vertigo and dizziness (VD). A number of clues from patient history and clinical examination, including several diagnostic index tests have been reported recently. The objective of the present study was to analyze frequency and distribution patterns of specific vestibular and non-vestibular diagnoses in an interdisciplinary university emergency room (ER), including data on daytime and season of presentation. A retrospective chart analysis of all patients seen in a one-year period was performed. In the ER 4.23% of all patients presented with VD (818 out of 19,345). The most frequent-specific diagnoses were BPPV (19.9%), stroke/transient ischemic attack (12.5%), acute unilateral vestibulopathy/vestibular neuritis (UVH; 8.3%), and functional VD (8.3%). Irrespective of the diagnosis, the majority of patients presented to the ER between 8 a.m. and 4 p.m. There are, however, seasonal differences. BPPV was most prevalent in December/January and rare in September. UVH was most often seen in October/November; absolute and relative numbers were lowest in August. Finally, functional/psychogenic VD was common in summer and autumn with highest numbers in September/October and lowest numbers in March. In summary, daytime of presentation did not distinguish between diagnoses as most patients presented during normal working hours. Seasonal presentation revealed interesting fluctuations. The UVH peak in autumn supports the viral origin of the condition (vestibular neuritis). The BPPV peak in winter might be related to reduced physical activity and low vitamin D. However, it is likely that multiple factors contribute to the fluctuations that have to be disentangled in further studies

A Prospective Analysis of Lesion-Symptom Relationships in Acute Vestibular and Ocular Motor Stroke

Background: Diagnosing stroke as a cause of acute vertigo, dizziness, or double vision remains a challenge, because symptom characteristics can be variable. The purpose of this study was to prospectively investigate lesion-symptom relationships in patients with acute vestibular or ocular motor stroke. Methods: Three hundred and fifty one patients with acute and isolated vestibular or ocular motor symptoms of unclear etiology were enrolled in the EMVERT lesion trial. Symptom quality was assessed by the chief complaint (vertigo, dizziness, double vision), symptom intensity by the visual analog scale, functional impairment by EQ-5D-5L, and symptom duration by daily rating. Acute vestibular and ocular motor signs were registered by videooculography. A standardized MRI (DWI-/FLAIR-/T2-/T2*-/3D-T1-weighted sequences) was recorded within 7 days of symptom onset. MRIs with DWI lesions were further processed for voxel-based lesion-symptom mapping (VLSM). Results: In 47 patients, MRI depicted an acute unilateral stroke (13.4%). The chief complaints were dizziness (42.5%), vertigo (40.4%) and double vision (17.0%). Lesions in patients with vertigo or dizziness showed a large overlap in the cerebellar hemisphere. VLSM indicated that strokes in the medial cerebellar layers 7b, 8, 9 were associated with vertigo, strokes in the lateral cerebellar layer 8, crus 1, 2 with dizziness, and pontomesencephalic strokes with double vision. Symptom intensity and duration varied largely between patients. Higher symptom intensity and longer duration were associated with medial cerebellar lesions. Hemispheric lesions of the cortex were rare and presented with milder symptoms of shorter duration. Conclusions: Prospective evaluation of patients with acute vestibular or ocular motor stroke revealed that symptom quality, intensity and duration were not suited to differentiating peripheral from central etiologies. Lesions in the lateral cerebellum, thalamus, or cortex presented with unspecific, mild and transient symptoms prone to being misdiagnosed

Gait analysis in PSP and NPH Dual-task conditions make the difference

Objective To test whether quantitative gait analysis of gait under single- and dual-task conditions can be used for a differential diagnosis of progressive supranuclear palsy (PSP) and idiopathic normalpressure hydrocephalus (iNPH). Methods In this cross-sectional study, temporal and spatial gait parameters were analyzed in 38 patients with PSP (Neurological Disorders and Stroke and Society for Progressive Supranuclear Palsy diagnostic criteria), 27 patients with iNPH (international iNPH guidelines), and 38 healthy controls. A pressure-sensitive carpet was used to examine gait under 5 conditions: single task (preferred, slow, and maximal speed), cognitive dual task (walking with serial 7 subtractions), and motor dual task (walking while carrying a tray). Results The main results were as follows. First, both patients with PSP and those with iNPH exhibited significant gait dysfunction, which was worse in patients with iNPH with a more broad-based gait (p < 0.001). Second, stride time variability was increased in both patient groups, more pronounced in PSP (p = 0.009). Third, cognitive dual task led to a greater reduction of gait velocity in PSP (PSP 34.4% vs iNPH 16.9%, p = 0.002). Motor dual task revealed a dissociation of gait performance: patients with PSP considerably worsened, but patients with iNPH tended to improve. Conclusion Patients with PSP seem to be more sensitive to dual-task perturbations than patients with iNPH. An increased step width and anisotropy of the effect of dual-task conditions (cognitive vs motor) seem to be good diagnostic tools for iNPH