Accelerometric Trunk Sensors to Detect Changes of Body Positions in Immobile Patients.

Mobilization, verticalization and position change are mandatory for severely affected neurological patients in early neurorehabilitation in order to improve neurological status and prevent complications. However, with the exception of hospitals and rehabilitation facilities, this activity is not usually monitored and so far the automated monitoring of position changes in immobile patients has not been investigated. Therefore, we investigated whether accelerometers on the upper trunk could reliably detect body position changes in immobile patients. Thirty immobile patients in early neurorehabilitation (Barthel Index ≤ 30) were enrolled. Two tri-axial accelerometers were placed on the upper trunk and on the thigh. Information on the position and position changes of the subject were derived from accelerometer data and compared to standard written documentation in the hospital over 24 h. Frequency and duration of different body positions (supine, sidelying, sitting) were measured. Data are presented as mean ± SEM. Groups were compared using one-way ANOVA or Kruskal-Wallis-test. Differences were considered significant if p < 0.05. Trunk sensors detected 100% and thigh sensors 66% of position changes (p = 0.0004) compared to standard care documentation. Furthermore, trunk recording also detected additional spontaneous body position changes that were not documented in standard care (81.8 ± 4.4% of all position changes were documented in standard care documentation) (p < 0.0001). We found that accelerometric trunk sensors are suitable for recording position changes and mobilization of severely affected patients. Our findings suggest that using accelerometers for care documentation is useful for monitoring position changes and mobilization frequencies in and outside of hospital for severely affected neurological patients. Accelerometric sensors may be valuable in monitoring continuation of care plans after intensive neurorehabilitation.

Anisotropy of Human Horizontal and Vertical Navigation in Real Space: Behavioral and PET Correlates.

Spatial orientation was tested during a horizontal and vertical real navigation task in humans. Video tracking of eye movements was used to analyse the behavioral strategy and combined with simultaneous measurements of brain activation and metabolism ([18F]-FDG-PET). Spatial navigation performance was significantly better during horizontal navigation. Horizontal navigation was predominantly visually and landmark-guided. PET measurements indicated that glucose metabolism increased in the right hippocampus, bilateral retrosplenial cortex, and pontine tegmentum during horizontal navigation. In contrast, vertical navigation was less reliant on visual and landmark information. In PET, vertical navigation activated the bilateral hippocampus and insula. Direct comparison revealed a relative activation in the pontine tegmentum and visual cortical areas during horizontal navigation and in the flocculus, insula, and anterior cingulate cortex during vertical navigation. In conclusion, these data indicate a functional anisotropy of human 3D-navigation in favor of the horizontal plane. There are common brain areas for both forms of navigation (hippocampus) as well as unique areas such as the retrosplenial cortex, visual cortex (horizontal navigation), flocculus, and vestibular multisensory cortex (vertical navigation). Visually guided landmark recognition seems to be more important for horizontal navigation, while distance estimation based on vestibular input might be more relevant for vertical navigation.

TMS of the left primary motor cortex improves tremor intensity and postural control in primary orthostatic tremor.

A ponto-cerebello-thalamo-cortical network is the pathophysiological correlate of primary orthostatic tremor. Affected patients often do not respond satisfactorily to pharmacological treatment. Consequently, the objective of the current study was to examine the effects of a non-invasive neuromodulation by theta burst repetitive transcranial magnetic stimulation (rTMS) of the left primary motor cortex (M1) and dorsal medial frontal cortex (dMFC) on tremor frequency, intensity, sway path and subjective postural stability in primary orthostatic tremor. In a cross-over design, eight patients (mean age 70.2 ± 5.4 years, 4 female) with a primary orthostatic tremor received either rTMS of the left M1 leg area or the dMFC at the first study session, followed by the other condition (dMFC or M1 respectively) at the second study session 30 days later. Tremor frequency and intensity were quantified by surface electromyography of lower leg muscles and total sway path by posturography (foam rubber with eyes open) before and after each rTMS session. Patients subjectively rated postural stability on the posturography platform following each rTMS treatment. We found that tremor frequency did not change significantly with M1- or dMFC-stimulation. However, tremor intensity was lower after M1- but not dMFC-stimulation (p = 0.033/ p = 0.339). The sway path decreased markedly after M1-stimulation (p = 0.0005) and dMFC-stimulation (p = 0.023) compared to baseline. Accordingly, patients indicated a better subjective feeling of postural stability both with M1-rTMS (p = 0.007) and dMFC-rTMS (p = 0.01). In conclusion, non-invasive neuromodulation particularly of the M1 area can improve postural control and tremor intensity in primary orthostatic tremor by interference with the tremor network.

Telemedical stroke care significantly improves patient outcome in rural areas: Long-term analysis of the German NEVAS network.

BACKGROUND: Comprehensive stroke centers (CSC) offer state-of-the-art stroke care in metropolitan centers. However, in rural areas, sufficient stroke expertise is much scarcer. Recently, telemedical stroke networks have offered instant consultation by stroke experts, enabling immediate administration of intravenous thrombolysis (IVT) on-site and decision on thrombectomy. While these immediate decisions are made during the consult, the impact of the network structures on stroke care in spoke hospitals is still not well described. AIMS: This study was performed to determine if on-site performance in rural hospitals and patient outcome improve over time through participation and regular medical staff training within a telemedical stroke network. METHODS: In this retrospective study, we analyzed data from stroke patients treated in four regional hospitals within the telemedical Neurovascular Network of Southwest Bavaria (NEVAS) between 2014 and 2019. We only included those patients that were treated in the regional hospitals until discharge at home or to neurorehabilitation. Functional outcome (modified Rankin scale) at discharge, mortality rate and periprocedural intracranial hemorrhage served as primary outcome parameters. Door-to-imaging and door-to-needle times were secondary outcome parameters. RESULTS: In 2014-2019, 5,379 patients were treated for acute stroke with 477 receiving IVT. Most baseline characteristics were comparable over time. For all stroke patients, door-to-imaging times increased over the years, but significantly improved for potential IVT candidates and those finally treated with IVT. The percentage of patients with door-to-needle time <30 min increased from 10% to 25%. Clinical outcome at discharge improved for all stroke patients treated in the regional hospitals. Particularly for patients treated with IVT, good clinical outcome (modified Rankin scale 0-2) at discharge increased from 2014 to 2019 by 19% and mortality rates dropped from 13% to 5%. CONCLUSIONS: 24-h/7-day telemedical support and regular on-site medical staff training within a structured telemedicine stroke network such as NEVAS significantly improve on-site stroke care in rural areas, leading to a considerable benefit in clinical outcome. DATA ACCESS STATEMENT: The data that support the findings of this study are available upon reasonable request and in compliance with the local and international ethical guidelines.

Impact of ongoing intravenous thrombolysis until completion of endovascular treatment in large vessel occlusion stroke patients.

Background: Recent studies have implied that ongoing intravenous thrombolysis (IVT) during endovascular treatment (ET) improves functional outcomes in patients who have undergone stroke caused by a large vessel occlusion (LVO). In this study, we investigated the effect of ongoing IVT until completion of ET on procedure duration, first-pass thrombectomy rate, and periprocedural complications. Methods: We analyzed patients from the German Stroke Registry-Endovascular Treatment dataset, collected between June 2015 and December 2021. Primary outcomes were modified Rankin Scale (mRS) score after 3 months and achievement of a Thrombolysis In Cerebral Infarction (TICI) score of 2b-3. Secondary parameters included ET duration, first-pass thrombectomy, and periprocedural complications. Results: Of the 13,082 patients in the dataset, 1,639 met the study inclusion criteria. A total of n = 317 patients (19.3%) underwent ongoing IVT until completion of ET, while IVT was completed prior to ET in 1,322 patients (80.7%). Ongoing IVT was associated with higher rates of achievement of an mRS score of 0-2 (or a back-to-baseline) after 3 months [odds ratio (OR) 1.53; 95% confidence interval (CI) 1.08-2.17]. Furthermore, ongoing IVT was predictive of achievement of a TICI score of 2b-3 (OR 1.37; 95% CI 1.03-1.83) and of first-pass thrombectomy (OR 2.07; 95% CI 1.51-2.84), while reducing the rate of peri-interventional complications (OR 0.64; 95% CI 0.44-0.94) and reducing ET duration by 24 min [ß = -24.35; 95% CI -32.92-(-15.79)]. Conclusion: Our findings suggest that ongoing IVT until ET completion has a favorable impact on both clinical and angiographic outcomes, as well as on periprocedural conditions, regardless of the overall time intervals involved. Therefore, rapid ET after IVT should be sought in order to take advantage of the additive effect of ongoing IVT during ET. Future studies should consider IVT timing in the context of ET as a potential confounder and treatment target.

Downbeat nystagmus becomes attenuated during walking compared to standing.

Downbeat nystagmus (DBN) is a common form of acquired fixation nystagmus related to vestibulo-cerebellar impairments and associated with impaired vision and postural imbalance. DBN intensity becomes modulated by various factors such as gaze direction, head position, daytime, and resting conditions. Further evidence suggests that locomotion attenuates postural symptoms in DBN. Here, we examined whether walking might analogously influence ocular-motor deficits in DBN. Gaze stabilization mechanisms and nystagmus frequency were examined in 10 patients with DBN and 10 age-matched healthy controls with visual fixation during standing vs. walking on a motorized treadmill. Despite their central ocular-motor deficits, linear and angular gaze stabilization in the vertical plane were functional during walking in DBN patients and comparable to controls. Notably, nystagmus frequency in patients was considerably reduced during walking compared to standing (p < 0.001). The frequency of remaining nystagmus during walking was further modulated in a manner that depended on the specific phase of the gait cycle (p = 0.015). These attenuating effects on nystagmus intensity during walking suggest that ocular-motor control disturbances are selectively suppressed during locomotion in DBN. This suppression is potentially mediated by locomotor efference copies that have been shown to selectively govern gaze stabilization during stereotyped locomotion in animal models.

Bilateral vestibulopathy causes selective deficits in recombining novel routes in real space.

The differential impact of complete and incomplete bilateral vestibulopathy (BVP) on spatial orientation, visual exploration, and navigation-induced brain network activations is still under debate. In this study, 14 BVP patients (6 complete, 8 incomplete) and 14 age-matched healthy controls performed a navigation task requiring them to retrace familiar routes and recombine novel routes to find five items in real space. [18F]-fluorodeoxyglucose-PET was used to determine navigation-induced brain activations. Participants wore a gaze-controlled, head-fixed camera that recorded their visual exploration behaviour. Patients performed worse, when recombining novel routes (p < 0.001), whereas retracing of familiar routes was normal (p = 0.82). These deficits correlated with the severity of BVP. Patients exhibited higher gait fluctuations, spent less time at crossroads, and used a possible shortcut less often (p < 0.05). The right hippocampus and entorhinal cortex were less active and the bilateral parahippocampal place area more active during navigation in patients. Complete BVP showed reduced activations in the pontine brainstem, anterior thalamus, posterior insular, and retrosplenial cortex compared to incomplete BVP. The navigation-induced brain activation pattern in BVP is compatible with deficits in creating a mental representation of a novel environment. Residual vestibular function allows recruitment of brain areas involved in head direction signalling to support navigation.

Study of cardiac autonomic function in drug-naïve, newly diagnosed epilepsy patients.

BACKGROUND: Epilepsy is associated with ictal autonomic dysfunction which may extend into the inter-ictal period. Antiepileptic drugs have often been blamed for cardiac autonomic dysfunction in epilepsy patients. In this study we have investigated cardiac autonomic parameters in order to evaluate autonomic functions of drug-naïve epilepsy patients. METHOD: Twenty drug-naïve patients (15 males and 5 females) with epilepsy, and an equal number of age and gender matched controls, were evaluated for short-term resting heart rate variability and conventional cardiovascular autonomic measurements. RESULTS: The mean age of patients was 29.30 +/- 9.80 yrs (17-55 yrs), mean age at seizure onset was 19.70 +/- 9.15 yrs (3-40 yrs) and mean length of time since last seizure was 5.60 +/- 7.00 days (1-30 days). While there was no difference in the resting heart rate or conventional autonomic test parameters, time domain heart rate variability measurements showed a decreased percentage of R-R intervals of less than 50 ms and root mean square of R-R intervals in patients, when compared to controls. Frequency domain parameters showed a decreased total power (patients: 1,796.58 +/- 1,052.45 ms2; controls: 2,934.23 +/- 1,767.06 ms2, p = 0.008). Parameters indicative of decreased vagal tone, i.e. decreased high frequency power and increased low to high frequency ratio (patients: 1.69 +/- 0.94; controls: 1.14 +/- 0.64, p = 0.045), were observed among patients compared to controls. CONCLUSION: Subtle but definite cardiac autonomic dysfunction, especially in vagal tone, was identified in drug-naïve, new-onset epilepsy patients. Seizures can cause long-term and often progressive cardiac autonomic dysfunction which may be independent of concomitant antiepileptic drugs.

Real-space navigation testing differentiates between amyloid-positive and -negative aMCI.

OBJECTIVE: To distinguish between patients with amyloid-positive (A+) and -negative (A-) amnestic mild cognitive impairment (aMCI) by simultaneously investigating navigation performance, visual exploration behavior, and brain activations during a real-space navigation paradigm. METHODS: Twenty-one patients with aMCI were grouped into A+ (n = 11) and A- cases by amyloid-PET imaging and amyloid CSF levels and compared to 15 healthy controls. Neuropsychological deficits were quantified by use of the Consortium to Establish a Registry for Alzheimer's Disease-plus cognitive battery. All participants performed a navigation task in which they had to find items in a realistic spatial environment and had to apply egocentric and allocentric route planning strategies. 18F-fluorodeoxyglucose was injected at the start to detect navigation-induced brain activations. Subjects wore a gaze-controlled, head-fixed camera that recorded their visual exploration behavior. RESULTS: A+ patients performed worse during egocentric and allocentric navigation compared to A- patients and controls (p < 0.001). Both aMCI subgroups used fewer shortcuts, moved more slowly, and stayed longer at crossings. Word-list learning, figural learning, and Trail-Making tests did not differ in the A+ and A- subgroups. A+ patients showed a reduced activation of the right hippocampus, retrosplenial, and parietal cortex during navigation compared to A- patients (p < 0.005). CONCLUSIONS: A+ patients with aMCI perform worse than A- patients with aMCI in egocentric and allocentric route planning because of a more widespread impairment of their cerebral navigation network. Navigation testing in real space is a promising approach to identify patients with aMCI with underlying Alzheimer pathology.

Assessment of pulmonary function in amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is characterised by diffuse and progressive death of motor neurons and deteriorating pulmonary functions. At diagnosis most patients with ALS usually do not have any respiratory complaints. However, sub-clinical pulmonary dysfunction is known. OBJECTIVE: To study pulmonary dysfunction in patients who clinically and electro-physiologically fulfil El escorial criteria of probable and definite ALS. METHODS: We performed a standard battery of pulmonary function tests (PFTs) including spirometry, maximum voluntary ventilation (MVV) and maximum inspiratory and expiratory pressure (MEP, MIP) on 63 patients fulfilling the El escorial criteria for probable and definite ALS. Results were compared between the El escorial groups, bulbar- and limb-onset ALS and with age- and sex-matched healthy volunteers, taken as controls. RESULTS: Only 11% of the patients had respiratory complaints at diagnosis. There was no statistical difference in pulmonary parameters between bulbar- and limb-onset ALS. The pulmonary dysfunction was restrictive. Both definite and probable ALS patients had significant reduction in all the measured pulmonary function parameters. The reduction in definite ALS patients was greater in forced vital capacity percent (FVC%) predicted, peak expiratory flow rate (PEFR) percent predicted and MIP. The proportion of patients with severe and very severe dysfunction was higher in the definite ALS group as compared to probable ALS group. CONCLUSIONS: Significant pulmonary dysfunction of restrictive type was noted in ALS patients. Both types of ALS, bulbar- and limb-onset, had similar levels of dysfunction.

Prolonged allocentric navigation deficits indicate hippocampal damage in TGA.

OBJECTIVE: To investigate long-term recovery of allocentric and egocentric spatial orientation as a sensitive marker for hippocampal and extrahippocampal network function in transient global amnesia (TGA). METHODS: A group of 18 patients with TGA performed an established real-space navigation paradigm, requiring allo- and egocentric spatial orientation abilities, 3 days (postacute stage) and 3 months (follow-up) after symptom onset. Visual exploration behavior and navigation strategy were documented by a gaze-controlled, head-fixed camera. Allo- and egocentric spatial orientation performance was compared to that of 12 age-matched healthy controls. Navigation-induced brain activations were measured using [18F]-fluorodeoxyglucose-PET in a subgroup of 8 patients in the postacute stage and compared to those of the controls. RESULTS: In the postacute stage, the patients navigated worse and had higher error rates than controls in allocentric (p = 0.002), but not in egocentric, route planning (p = 0.30), despite complete recovery of verbal (p = 0.58) and figural memory (p = 0.11). Until follow-up, allocentric navigation deficits improved, but higher error rates and reduced use of shortcuts persisted (p < 0.0001). Patients still exhibited relatively more fixations of unique landmarks during follow-up (p = 0.05). PET measurements during the postacute stage showed increased navigation-induced brain activations in the right hippocampus, bilateral retrosplenial, parietal, and mesiofrontal cortices, and cerebellar dentate nucleus in patients compared to controls (p < 0.005). CONCLUSIONS: Patients with TGA show selective and prolonged deficits of allocentric spatial orientation. Activations in right hippocampal and extrahippocampal hubs of the cerebral navigation network functionally substitute for the deficit in creating and updating the internal cognitive map in TGA.

Noninvasive cardiac output measurement by transthoracic electrical bioimpedence: influence of age and gender.

BACKGROUND: Thoracic electrical bioimpedance (TEB) as a method of measuring cardiac output (CO) is being explored increasingly over the last two decades, as a non-invasive alternative to the pulmonary artery catheter. The objective of this study was to establish normative data for measurement of CO by TEB and define the effect of age and gender on CO. METHOD: Stroke volume (SV) of 397 normal individuals (203 men, 194 women) in the age range of 10-77 years was determined using Kubisek and Bernstein formulae by TEB method. Derived cardiac parameters including CO, cardiac index (CI), systemic vascular resistance and resistance index were calculated and analyzed. RESULTS: We found significant difference in CO among age groups and between gender. CO between Kubicek formula and Bernstein formula correlated well, but their means differed significantly. Cardiac indices peak in the third and seventh decade and were comparable between genders. CONCLUSION: A comprehensive data set of normalized values expressed as 95% confidence interval and mean +/- SD in different age groups and different gender was possible for cardiac parameters using TEB.

Noisy Galvanic Stimulation Improves Roll-Tilt Vestibular Perception in Healthy Subjects.

It has recently been demonstrated that noisy galvanic vestibular stimulation (nGVS) delivered as imperceptible white noise can improve balance control via the induction of stochastic resonance. However, it is unclear whether these balance improvements are accompanied by simultaneous enhancement to vestibular motion perception. In this study, 15 healthy subjects performed 8 quiet-stance tasks on foam with eyes closed at 8 different nGVS amplitudes ranging from 0 mA (baseline) to 0.5 mA. The nGVS amplitude that improved balance performance most compared to baseline was assigned as the optimal nGVS amplitude. Optimal nGVS amplitudes could be determined for 13 out of 15 subjects, who were included in the subsequent experimental procedures. The effect of nGVS delivered at the determined optimal intensity on vestibular perceptual thresholds was examined using direction-recognition tasks on a motion platform, testing roll rotations at 0.2, 0.5, and 1.0 Hz, both with active and sham nGVS stimulations. nGVS significantly reduced direction-recognition thresholds compared to the sham condition at 0.5 and 1.0 Hz, while no significant effect of nGVS was found at 0.2 Hz. Interestingly, no correlation was found between nGVS-induced improvements in balance control and vestibular motion perception at 0.5 and 1 Hz, which may suggest different mechanisms by which nGVS affects both modalities. For the first time, we show that nGVS can enhance roll vestibular motion perception. The outcomes of this study are likely to be relevant for the potential therapeutic use of nGVS in patients with balance problems.

Transient topographical disorientation due to right-sided hippocampal hemorrhage.

INTRODUCTION: Topographical disorientation is defined as the inability to recognize familiar or unfamiliar environments. While its slowly progressive development is a common feature of neurodegenerative processes like Alzheimer's dementia, acute presentations are less frequent and mostly caused by strategic lesions within the cerebral navigation network. Depending on the lesion site, topographical disorientation can originate from deficits in landmark recognition and utilization for route planning (egocentric navigation deficit), or disturbance of an overarching cognitive map of the spatial environment (allocentric navigation deficit). However, objective measurements of spatial navigation performance over time are largely missing in patients with topographical disorientation. METHODS: We here report a 55-year-old patient with acute topographical disorientation as the single symptom of right-sided hippocampal hemorrhage and present quantitative gaze-monitoring head camera-based analyses of his path-finding strategy and visual exploration behavior in a real space navigation paradigm. RESULTS: The patient exhibited severe allocentric and also egocentric navigation deficits during the acute phase, shown by higher error rates at finding target items. In addition, he showed a more extensive use of search saccades toward, and fixations on, landmarks that could potentially serve as spatial cues. These deficits had been completely compensated for after four months, when the patient performed unremarkably in the real space navigation task, and used even more strongly allocentric path optimization strategies than age-matched controls. CONCLUSIONS: This case report highlights the integral function and right-sided dominance of the hippocampal formation in the cerebral navigation network in humans. It shows that the cognitive map can be restored completely despite a residual hippocampal lesion, which illustrates the enormous plasticity of the cerebral navigation network in humans.

A novel real-space navigation paradigm reveals age- and gender-dependent changes of navigational strategies and hippocampal activation.

OBJECTIVE: To establish a novel multimodal real-space navigation paradigm and define age- and gender-related normative values for navigation performance and visual exploration strategies in space. METHODS: A group of 30 healthy subjects (mean age 45.9 ± 16.5 years, 16 men) performed a real-space navigation paradigm, requiring allo- and egocentric spatial orientation abilities. Visual exploration behaviour and navigation strategy were documented by a gaze-controlled, head-fixed camera. Allo- and egocentric spatial orientation performance were compared in younger and older subjects (age threshold 50 years) as well as men and women. Navigation-induced changes of regional cerebral glucose metabolism (rCGM) were measured by [18F]-fluorodeoxyglucose-positron emission tomography in a subgroup of 15 subjects (8 men) and compared across age and gender. RESULTS: The majority of healthy subjects (73.3%) completed the navigation task without errors. There was no gender difference in navigation performance. Normalized total error rates increased slightly, but significantly with age (r = 0.36, p = 0.05). Analysis of navigation path indicated a significantly reduced use of short cuts in older age (r = 0.44, p = 0.015). Visual exploration analysis revealed that older subjects made significantly more total saccades (r = 0.49, p = 0.006) and search saccades (r = 0.54, p = 0.002) during navigation. All visual exploration parameters were similar in men and women. Navigation-induced rCGM decreased with age in the hippocampus and precuneus and increased in the frontal cortex, basal ganglia and cerebellum. Women showed an increase of rCGM in the left hippocampus and right middle temporal gyrus, men in the superior vermis. CONCLUSION: Real-space navigation testing was a feasible and sensitive method to depict age-related changes in navigation performance and strategy. Normalized error rates, total mean durations per item and total number of saccades were the most sensitive and practical parameters to indicate deterioration of allocentric navigation strategies and right hippocampal function in age irrespective of gender.

Clinical and neurophysiological risk factors for falls in patients with bilateral vestibulopathy.

Patients with bilateral vestibular failure (BVF) exhibit imbalance when standing and walking that is linked to a higher fall risk. The purpose of this study was to identify risk factors for falls in BVF. We therefore systematically investigated the interrelationship of clinical and demographic characteristics, gait impairments, and the fall frequency of these patients. Clinical and demographic characteristics as well as quantitative measures of gait performance on a pressure-sensitive gait carpet were collected from 55 patients with different etiologies of BVF. Clinical and demographic data as well as spatiotemporal gait characteristics were used for ANOVA testing and a logistic regression model with categorized fall events as dependent variables. The impairment of peripheral vestibular function, duration of disease, and the overall gait status were not associated with the history of falls in patients with BVF. In contrast, the most predictive factors for falls in BVF were an increase in temporal gait variability, especially at slow walking speeds (p < 0.001; OR = 1.3), and the presence of a concomitant peripheral neuropathy (p < 0.045; OR = 3.6). BVF patients with a high risk of falling exhibit specific gait alterations in a speed-dependent manner. In particular, increased gait fluctuations during slow walking are most predictive for an increased fall risk. The presence of a concomitant peripheral neuropathy further critically impairs postural stability in these patients. Clinical assessment of both these aspects is therefore important to identify those patients at a particularly high fall risk and to initiate preventive procedures early.

The interrelationship between disease severity, dynamic stability, and falls in cerebellar ataxia.

Cerebellar ataxia (CA) results in discoordination of body movements (ataxia), a gait disorder, and falls. All three aspects appear to be obviously interrelated; however, experimental evidence is sparse. This study systematically correlated the clinical rating of the severity of ataxia with dynamic stability measures and the fall frequency in patients with CA. Clinical severity of CA in patients with sporadic (n = 34) and hereditary (n = 24) forms was assessed with the Scale for the Assessment and Rating of Ataxia (SARA). Gait performance was examined during slow, preferred, and maximally fast walking speeds. Spatiotemporal variability parameters in the fore-aft and medio-lateral directions were analyzed. The fall frequency was assessed using a standardized interview about fall events within the last 6 months. Fore-aft gait variability showed significant speed-dependent characteristics with highest magnitudes during slow and fast walking. The SARA score correlated positively with fore-aft gait variability, most prominently during fast walking. The fall frequency was significantly associated to fore-aft gait variability during slow walking. Severity of ataxia, dynamic stability, and the occurrence of falls were interrelated in a speed-dependent manner: (a) Severity of ataxia symptoms was closely related to instability during fast walking. (b) Fall frequency was associated with instability during slow walking. These findings suggest the presence of a speed-dependent, twofold cerebellar locomotor control. Assessment of gait performance during non-preferred, slow and fast walking speeds provides novel insights into the pathophysiology of cerebellar locomotor control and may become a useful approach in the clinical evaluation of patients with CA.

Automated classification of neurological disorders of gait using spatio-temporal gait parameters.

OBJECTIVE: Automated pattern recognition systems have been used for accurate identification of neurological conditions as well as the evaluation of the treatment outcomes. This study aims to determine the accuracy of diagnoses of (oto-)neurological gait disorders using different types of automated pattern recognition techniques. METHODS: Clinically confirmed cases of phobic postural vertigo (N = 30), cerebellar ataxia (N = 30), progressive supranuclear palsy (N = 30), bilateral vestibulopathy (N = 30), as well as healthy subjects (N = 30) were recruited for the study. 8 measurements with 136 variables using a GAITRite(®) sensor carpet were obtained from each subject. Subjects were randomly divided into two groups (training cases and validation cases). Sensitivity and specificity of k-nearest neighbor (KNN), naive-bayes classifier (NB), artificial neural network (ANN), and support vector machine (SVM) in classifying the validation cases were calculated. RESULTS: ANN and SVM had the highest overall sensitivity with 90.6% and 92.0% respectively, followed by NB (76.0%) and KNN (73.3%). SVM and ANN showed high false negative rates for bilateral vestibulopathy cases (20.0% and 26.0%); while KNN and NB had high false negative rates for progressive supranuclear palsy cases (76.7% and 40.0%). CONCLUSIONS: Automated pattern recognition systems are able to identify pathological gait patterns and establish clinical diagnosis with good accuracy. SVM and ANN in particular differentiate gait patterns of several distinct oto-neurological disorders of gait with high sensitivity and specificity compared to KNN and NB. Both SVM and ANN appear to be a reliable diagnostic and management tool for disorders of gait.

Patterns of optimization in single- and inter-leg gait dynamics.

INTRODUCTION: We examined the influence of walking speed on the fluctuation and synchronization dynamics of stride intervals and ground reaction force (GRF) profiles. Our aim was to identify patterns of optimization in the single-leg and inter-leg dynamics at preferred walking speed (PWS). PWS is thought to bring about the most stable walking pattern in terms of the attractor dynamics of the locomotion system. METHODS: Twenty healthy subjects (29.1 ± 1.8 years; 10 women) walked on a treadmill for 5-min periods at their PWS and at 20, 40, 70, and 80% of maximal walking speed. The coefficient of variation (CV) and long-range correlations α of GRF profile and stride time fluctuations as well as the phase synchronization ρ of inter-leg stride timing were analyzed. RESULTS: GRF profile α increased with increasing walking speed (p < 0.001). In contrast, stride time CV and α showed a U-shaped speed-dependency with lowest values at PWS (p < 0.05). The speed-dependency of single-leg stride time fluctuations was mirror-inverted in the speed-dependency of inter-leg stride timing ρ; its highest values occurred at PWS (p < 0.001). CONCLUSIONS: Fluctuations in GRF profiles become more consistent with increasing walking speed. In contrast, the dynamics of single-leg and inter-leg timing show a collective pattern of optimization at PWS. Less correlated noise in single-leg timing at PWS, imposed on the two coupled oscillating legs, increases the phase synchronization of bilateral timing, thereby enhancing gait stability at the attractor of self-paced walking. Thus, the attractor dynamics of locomotion appear to rely on the interaction of single- and inter-leg timing.

Gait characteristics of patients with phobic postural vertigo: effects of fear of falling, attention, and visual input.

Phobic postural vertigo (PPV) is the most common cause of chronic dizziness in middle-aged patients. Many patients report symptoms involving gait. We investigated the gait performance and its relationship to the fear of falling and attention of PPV patients in a prospective study of 24 patients with PPV and 24 healthy subjects (HS) using a pressure-sensitive mat (GAITRite(®)). Subjects walked at three different speeds (slow, preferred, fast), both during cognitive dual tasks (DTc) and with eyes closed (EC). Falls efficacy and balance confidence were rated by the Falls Efficacy Scale-International (FES-I) and the Activities-specific Balance Confidence Scale (ABC). PPV patients walked slower, with reduced cadence (all p < 0.01), stride length (p < 0.05), and increased double support (p < 0.01) compared to HS. These changes correlated with FES-I (R = -0.528, p < 0.001) and ABC (R = 0.481, p < 0.01). Walking deterioration under DTc did not differ between PPV patients and HS, but patients showed a reduced cognitive processing speed (p < 0.05). When walking with EC, gait speed decreased more in PPV patients compared to HS (p < 0.05). Patients with PPV show gait changes which correlate with their fear of falling and balance confidence. Absent visual feedback leads to more pronounced gait deteriorations in PPV patients than in HS, indicating a higher reliance of patients on visual information during walking. These findings support the view that the gait characteristics of PPV can be attributed to an inadequate, cautious gait control.