Normal pressure hydrocephalus and cognitive impairment: The gait phenotype matters too.

BACKGROUND AND PURPOSE: Idiopathic normal pressure hydrocephalus (iNPH) is a chronic neurological disease resulting in progressive gait and cognitive disorders. We investigated whether the gait phenotype is associated with the severity of cognitive deficits in iNPH. METHODS: This retrospective study recruited 88 patients (mean age = 76.18 ± 7.21 years, 42% female). Patients were initially referred for suspicion of iNPH and underwent a comprehensive analysis, including gait analysis and cognitive evaluation. RESULTS: In this cohort (27% normal gait, 25% frontal gait, 16% parkinsonian gait, 27% other gait abnormalities), patients with parkinsonian and frontal gait had the lowest Mini-Mental State Examination (MMSE) scores and the slowest gait speed. Patients with normal gait had the highest MMSE scores and gait speed. Frontal gait was associated with lower MMSE score, even after adjusting for age, gender, comorbidities, white matter lesions, and education level (ß = -0.221 [95% confidence interval (CI) = -3.718 to -0.150], p = 0.034). Normal gait was associated with the best MMSE scores, even after adjusting for the abovementioned variables (ß = 0.231 [95% CI = 0.124-3.639], p = 0.036). CONCLUSIONS: Gait phenotypes among iNPH patients are linked to global cognition as assessed with MMSE.

The contribution of cognitive reserve in explaining the dual-task walking performance in iNPH patients: comparison with other cognitive, functional, and socio-demographic variables.

BACKGROUND: Idiopathic normal pressure hydrocephalus (iNPH) is a prevalent neurological disorder, but its diagnosis remains challenging. Dual-task (DT) walking performance is a reliable indicator of iNPH but less is known about the role of cognitive reserve (CR) in predicting DT walking performance. AIMS: The objective of this study was to evaluate the contribution of CR on DT walking in healthy controls (HC) and in iNPH patients (iNPH-P). METHODS: 68 iNPH-P (77.2 +/- 6.7 years old) and 28 HC (74.5 +/- 5.7 years old) were evaluated on their single-task walking (Vsimple) and on 4 DT walking (walking and counting or counting backwards, naming animals, naming words beginning with the letter P) (Vcount, VcountB, Vanimals and Vletter respectively). The contribution of CR on the different DT walking speeds was compared between HC and iNPH-P. In iNPH-P, the contribution of CR on the walking speeds was compared with regard to other cognitive, functional, and socio-demographic variables. RESULTS: Simple linear regression demonstrated a moderate influence of CR on single and DT walking speed in iNPH-P (ß > 0.3, p < .001) but not in HC where the relation was not significant. In iNPH-P, results showed that CR played a major role in explaining each of the single and DT walking speeds with NPH-scale. CONCLUSION: As CR could be improved through the life cycle, these results support the idea of developing and supporting physical activity programs that will enrich social, physical, and cognitive resources to protect against age-related functional decline, especially in iNPH-P patients where the age-related deficits are greater.

Sensor-to-Bone Calibration with the Fusion of IMU and Bi-Plane X-rays.

Inertial measurement units (IMUs) need sensor-to-segment calibration to measure human kinematics. Multiple methods exist, but, when assessing populations with locomotor function pathologies, multiple limitations arise, including holding postures (limited by joint pain and stiffness), performing specific tasks (limited by lack of selectivity) or hypothesis on limb alignment (limited by bone deformity and joint stiffness). We propose a sensor-to-bone calibration based on bi-plane X-rays and a specifically designed fusion box to measure IMU orientation with respect to underlying bones. Eight patients undergoing total hip arthroplasty with bi-plane X-rays in their clinical pathway participated in the study. Patients underwent bi-plane X-rays with fusion box and skin markers followed by a gait analysis with IMUs and a marker-based method. The validity of the pelvis, thigh and hip kinematics measured with a conventional sensor-to-segment calibration and with the sensor-to-bone calibration were compared. Results showed (1) the feasibility of the fusion of bi-plane X-rays and IMUs in measuring the orientation of anatomical axes, and (2) higher validity of the sensor-to-bone calibration for the pelvic tilt and similar validity for other degrees of freedom. The main strength of this novel calibration is to remove conventional hypotheses on joint and segment orientations that are frequently violated in pathological populations.

Reliability of the Harris Hip limping sub-score in patients undergoing total hip arthroplasty.

PURPOSE: In patients undergoing total hip arthroplasty, limping is a significant symptom, often assessed with the limping sub-score of the Harris Hip Score. However, the reliability of this sub-score has not been specifically investigated. The purpose of this study is to investigate the intra- and inter-rater reliability of this sub-score. METHODS: Thirty patients undergoing THA were recruited and performed a gait analysis before surgery and three months after surgery. In addition, 30 asymptomatic participants were included. In total, 90 visits were analysed in this study. The HHS limping sub-score was assessed for each visit using a video (front and back view side-by-side) of a ten metre walk at a self-selected speed. Two orthopaedic surgeons evaluated the limping of each video in two different grading sessions with a one week delay. To avoid recall bias, the patient's number identity was randomized and different for each grading session and each rater. The weighted Cohen's Kappa coefficient was used to quantify the intra- and inter-reliability. The reliability of three components was studied: the presence of limping, its severity, and the compensation type. RESULTS: For all components, the agreement for intra-rater reliability ranged from moderate to strong and from none to moderate for the inter-rater reliability. CONCLUSION: These results do not encourage the use of HHS-limping sub-score for data involving different raters in both clinical and research contexts. It calls for improved consensus on limping definitions or the creation of objective measures.

Investigation of neural and biomechanical impairments leading to pathological toe and heel gaits using neuromusculoskeletal modelling.

This study investigates the pathological toe and heel gaits seen in human locomotion using neuromusculoskeletal modelling and simulation. In particular, it aims to investigate potential cause-effect relationships between biomechanical or neural impairments and pathological gaits. Toe and heel gaits are commonly present in spinal cord injury, stroke and cerebral palsy. Toe walking is mainly attributed to spasticity and contracture at plantar flexor muscles, whereas heel walking can be attributed to muscle weakness of biomechanical or neural origin. To investigate the effect of these impairments on gait, this study focuses on the soleus and gastrocnemius muscles as they contribute to ankle plantarflexion. We built a reflex circuit model based on previous work by Geyer and Herr with additional pathways affecting the plantar flexor muscles. The SCONE software, which provides optimisation tools for 2D neuromechanical simulation of human locomotion, is used to optimise the corresponding reflex parameters and simulate healthy gait. We then modelled various bilateral plantar flexor biomechanical and neural impairments, and individually introduced them in the healthy model. We characterised the resulting simulated gaits as pathological or not by comparing ankle kinematics and ankle moment with the healthy optimised gait based on metrics used in clinical studies. Our simulations suggest that toe walking can be generated by hyperreflexia, whereas muscle and neural weaknesses partially induce heel gait. Thus, this 'what if' approach is deemed of great interest as it allows investigation of the effect of various impairments on gait and suggests an important contribution of active reflex mechanisms to pathological toe gait. KEY POINTS: Pathological toe and heel gaits are commonly present in various conditions such as spinal cord injury, stroke and cerebral palsy. These conditions present various neural and biomechanical impairments, but the cause-effect relationships between these impairments and pathological gaits are difficult to establish clinically. Based on neuromechanical simulation, this study focuses on the plantar flexor muscles and builds a new reflex circuit controller to model and evaluate the potential effect of both neural and biomechanical impairments on gait. Our results suggest an important contribution of active reflex mechanisms to pathological toe gait. This 'what if' based on neuromechanical modelling is thus deemed of great interest to target potential causes of pathological gait.

Sensory modulation of gait characteristics in human locomotion: A neuromusculoskeletal modeling study.

The central nervous system of humans and other animals modulates spinal cord activity to achieve several locomotion behaviors. Previous neuromechanical models investigated the modulation of human gait changing selected parameters belonging to CPGs (Central Pattern Generators) feedforward oscillatory structures or to feedback reflex circuits. CPG-based models could replicate slow and fast walking by changing only the oscillation's properties. On the other hand, reflex-based models could achieve different behaviors through optimizations of large dimensional parameter spaces. However, they could not effectively identify individual key reflex parameters responsible for gait characteristics' modulation. This study investigates which reflex parameters modulate the gait characteristics through neuromechanical simulations. A recently developed reflex-based model is used to perform optimizations with different target behaviors on speed, step length, and step duration to analyze the correlation between reflex parameters and their influence on these gait characteristics. We identified nine key parameters that may affect the target speed ranging from slow to fast walking (0.48 and 1.71 m/s) as well as a large range of step lengths (0.43 and 0.88 m) and step duration (0.51, 0.98 s). The findings show that specific reflexes during stance significantly affect step length regulation, mainly given by positive force feedback of the ankle plantarflexors' group. On the other hand, stretch reflexes active during swing of iliopsoas and gluteus maximus regulate all the gait characteristics under analysis. Additionally, the results show that the hamstrings' group's stretch reflex during the landing phase is responsible for modulating the step length and step duration. Additional validation studies in simulations demonstrated that the modulation of identified reflexes is sufficient to regulate the investigated gait characteristics. Thus, this study provides an overview of possible reflexes involved in modulating speed, step length, and step duration of human gaits.

Assessment of gait quality and efficiency after undergoing a single-event multilevel surgery in children with cerebral palsy presenting an intoeing gait pattern.

PURPOSE: The biomechanical impact of undergoing a single-event multilevel surgery (SEMLS) for children with cerebral palsy (CP) presenting an intoeing gait pattern has been widely documented. However, past studies mostly focused on gait quality rather than efficiency. Thus, there is a need to determine the impact of undergoing a SEMLS on gait quality and efficiency in children with CP presenting an intoeing gait pattern. METHODS: Data from 16 children with CP presenting an intoeing gait pattern who underwent a SEMLS were retrospectively selected. Gait kinematics was quantified before (baseline) and at least 1 year after the surgery (follow-up). Gait quality was investigated with the Gait Profile Score (GPS), hip internal rotation angle and foot progression angle (FPA). Gait efficiency was analysed using clinically accessible variables, namely the normalised gait speed and medio-lateral and vertical centre of mass excursions (COMp). Dependent variables were compared between sessions with paired t-tests. RESULTS: At the follow-up, children with CP exhibited a more outward FPA and GPS as well as a decreased hip internal rotation angle. No changes in normalised gait speed and vertical COMp excursion were observed, and medio-lateral COMp excursion was slightly decreased. CONCLUSION: Children with CP presenting an intoeing gait pattern who underwent a SEMLS exhibited an increased gait quality, but gait efficiency was only minimally improved at the follow-up compared to baseline. Further studies are needed to identify contributors of gait efficiency in children with CP, and the best treatment modalities to optimise both their gait quality and efficiency.

The flexion relaxation phenomenon in nonspecific chronic low back pain: prevalence, reproducibility and flexion-extension ratios. A systematic review and meta-analysis.

PURPOSE: The flexion relaxation phenomenon (FRP) is characterized by the reduction of paraspinal muscle activity at maximum trunk flexion. The FRP is reported to be altered (persistence of spinal muscle activity) in nonspecific chronic low back pain (NSCLBP) and is considered a promising biomarker. The aim of this systematic review was to synthetize current knowledge on FRP in the NSCLBP population regarding prevalence, the reliability of FRP measurement using surface electromyography (sEMG), the average value, and variation of the relaxation ratios (RR). METHODS: Five databases were searched (PubMed, EMBASE, Web of Sciences, Cochrane Library, Pedro). A qualitative analysis was done for all included studies and meta-analysis studying prevalence, mean value of flexion relaxation ratio (FRR) and extension relaxation ratio (ERR), and difference between asymptomatic and NSCLBP FRR. RESULTS: Twenty-seven studies were included for qualitative analysis and 21 studies for meta-analysis. The prevalence of the altered FRP was 55% (95%CI [32-79%]) in the NSCLBP population. The studies on reliability reported good within-session and between-session reproducibility. In the NSLBP population, the mean FRR was 2.96 (95%CI [2.02; 3.90]) and the mean ERR was 4.07 (95%CI [2.08; 6.07]). The difference between asymptomatic and NSCLBP FRR was - 1.19 (95%CI [- 1.92, - 0.45]). In all meta-analysis, the I2 index was > 80%. CONCLUSION: An altered FRP is frequently found in NSCLBP population using sEMG and the test has a good reproducibility. The difference between asymptomatic and NSCLBP FRR was significant. Nevertheless, considering the high heterogeneity observed, additional research is required to confirm the value of RR.

Three-Dimensional Lower-Limb Kinematics from Accelerometers and Gyroscopes with Simple and Minimal Functional Calibration Tasks: Validation on Asymptomatic Participants.

The use of inertial measurement units (IMUs) to compute gait outputs, such as the 3D lower-limb kinematics is of huge potential, but no consensus on the procedures and algorithms exists. This study aimed at evaluating the validity of a 7-IMUs system against the optoelectronic system. Ten asymptomatic subjects were included. They wore IMUs on their feet, shanks, thighs and pelvis. The IMUs were embedded in clusters with reflective markers. Reference kinematics was computed from anatomical markers. Gait kinematics was obtained from accelerometer and gyroscope data after sensor orientation estimation and sensor-to-segment (S2S) calibration steps. The S2S calibration steps were also applied to the cluster data. IMU-based and cluster-based kinematics were compared to the reference through root mean square errors (RMSEs), centered RMSEs (after mean removal), correlation coefficients (CCs) and differences in amplitude. The mean RMSE and centered RMSE were, respectively, 7.5° and 4.0° for IMU-kinematics, and 7.9° and 3.8° for cluster-kinematics. Very good CCs were found in the sagittal plane for both IMUs and cluster-based kinematics at the hip, knee and ankle levels (CCs > 0.85). The overall mean amplitude difference was about 7°. These results reflected good accordance in our system with the reference, especially in the sagittal plane, but the presence of offsets requires caution for clinical use.

[New tools for movement assessment in children with motor disabilities]. / Nouveaux outils d'évaluation du mouvement chez l'enfant avec handicap moteur.

Until recently, movement analysis of children with motor disabilities has mainly relied on in-lab measurements using optoelectronic systems. The development of new tools is mainly inspired from mainstream devices, such as video cameras associated with artificial intelligence or inertial sensors. These tools have extended the assessment of movement in these children beyond traditional movement analysis laboratories, to take an interest in their movements in everyday life. Through the complementarity of these measurements (and associated tools), which the use of is becoming mainstream, a more exhaustive understanding of children's motor disorders and their impacts will allow clinicians to optimize their therapeutic management.

Jusqu'à récemment l'analyse du mouvement chez l'enfant avec handicap moteur s'est principalement appuyée sur des mesures détaillées effectuées en laboratoire à l'aide de systèmes optoélectroniques. Le développement de nouveaux outils de mesure s'appuie sur des dispositifs grand public, tels que les caméras vidéo associées à de l'intelligence artificielle ou les capteurs inertiels. Ces outils ont permis d'étendre le champ d'exploration du mouvement de ces enfants hors des laboratoires traditionnels d'analyse du mouvement pour s'intéresser à leurs mouvements dans la vie quotidienne. Par la complémentarité de ces mesures (et outils associés), dont l'utilisation est appelée à se démocratiser, une compréhension plus exhaustive des troubles moteurs de l'enfant et de ses impacts permettra d'optimiser leur prise en charge thérapeutique.

Normal pressure hydrocephalus and CSF tap test response: the gait phenotype matters.

This study compared gait speed changes after CSF tap test in patients with idiopathic normal pressure hydrocephalus presenting with various gait phenotypes (frontal, parkinsonian, normal, or other). All patients improved, except those with parkinsonian gait.

Self-perceived gait quality in young adults with cerebral palsy.

AIM: To explore how patients with cerebral palsy (CP) perceive their gait and evaluate associations between subjective gait perception and: objective gait parameters, endurance, pain, and fatigue. METHOD: Sixty-two patients (21 females and 41 males; mean [SD] age 20y [5y 1mo], range 15-29y) performed a clinical gait analysis. Self-selected walking speed, Gait Profile Score, and Gait Variable Score were calculated. Subjective gait perception was assessed with a visual analogue scale using the question: 'On a scale from 0 (worst) to 10 (optimal), how would you describe your walking today?'. A 6-minute walk test (6MWT) measured endurance; the 36-Item Short Form Health Survey (SF-36) evaluated quality of life. T-tests, Pearson correlations, and univariate and multiple linear regression models were used to compare and find associations between the data. RESULTS: Overall mean (SD) subjective gait perception was 7.5 (1.8) and was significantly higher for patients in Gross Motor Function Classification System (GMFCS) level I (7.9 [1.5]) than for patients in GMFCS levels II and III (5.9 [2.0]). Positive correlations were found between subjective gait perception and gait scores, walking speed, 6MWT distance, and SF-36 score. Only walking speed was a significant predictor of subjective gait perception. INTERPRETATION: Subjective gait perception was influenced by GMFCS level and linked partially with the walking speed. The gait quality did not explain subjective gait perception. It is important to combine subjective and objective gait scores to develop personalized therapeutic goals. WHAT THIS PAPER ADDS: Subjective gait perception is influenced by the physical impairment levels of patients with cerebral palsy. Subjective gait perception and objective gait scores are associated. Walking speed is the only predictor of gait perception.

Walking Speed and Maximal Knee Flexion During Gait After Total Knee Arthroplasty: Minimal Clinically Important Improvement Is Not Determinable; Patient Acceptable Symptom State Is Potentially Useful.

BACKGROUND: Total knee arthroplasty (TKA) is the operation of choice in patients with end-stage knee osteoarthritis (OA). Up to 1 in 5 patients still encounter functional limitations after TKA, partly explaining patient dissatisfaction. Which gait ability to target after TKA remains unclear. To determine whether Minimal Clinical Important Improvement (MCII) or Patient Acceptable Symptom State (PASS) values could be derived from gait parameters recorded in patients with TKA. And, if so, to define those values. METHODS: In this ancillary study, we retrospectively analyzed gait parameters of patients scheduled for a unilateral TKA between 2011 and 2013. We investigated MCII and PASS values for walking speed and maximal knee flexion using anchor-based methods: 5 anchoring questions based on perceived body function and patients' satisfaction. RESULTS: Over the study period, 79 patients performed a clinical gait analysis the week before and 1 year after surgery, and were included in the present study. All clinical and gait parameters improved 1 year after TKA. Nevertheless, changes in gait outcomes were not associated with perceived body function or patients' satisfaction, precluding any MCII estimation in gait parameters. PASS values, however, could be determined as 1.2 m/s for walking speed and 50° for maximal knee flexion. CONCLUSION: In this study, we found that MCII and PASS values are not necessarily determinable for gait parameters after TKA in patients with end-stage OA. Using anchor questions based on perceived body function and patient's satisfaction, MCII could not be defined while PASS values were potentially useful. LEVEL OF EVIDENCE: Level III.

Multidimensional Measures of Physical Activity and Their Association with Gross Motor Capacity in Children and Adolescents with Cerebral Palsy.

The current lack of adapted performance metrics leads clinicians to focus on what children with cerebral palsy (CP) do in a clinical setting, despite the ongoing debate on whether capacity (what they do at best) adequately reflects performance (what they do in daily life). Our aim was to measure these children's habitual physical activity (PA) and gross motor capacity and investigate their relationship. Using five synchronized inertial measurement units (IMU) and algorithms adapted to this population, we computed 22 PA states integrating the type (e.g., sitting, walking, etc.), duration, and intensity of PA. Their temporal sequence was visualized with a PA barcode from which information about pattern complexity and the time spent in each of the six simplified PA states (PAS; considering PA type and duration, but not intensity) was extracted and compared to capacity. Results of 25 children with CP showed no strong association between motor capacity and performance, but a certain level of motor capacity seems to be a prerequisite for the achievement of higher PAS. Our multidimensional performance measurement provides a new method of PA assessment in this population, with an easy-to-understand visual output (barcode) and objective data for clinical and scientific use.

Asymmetry of lumbar muscles fatigability with non-specific chronic low back pain patients.

PURPOSE: Non-specific chronic low back pain (NSCLBP) patients present with reduced back extensor muscle endurance which could be explained by the higher fatigability of their lumbar muscles. However, studies investigating lumbar muscle fatigability have shown contradictory findings. Furthermore, none investigated potential asymmetry in lumbar muscle fatigability, despite neuromuscular asymmetry being reported as a risk factor for NSCLBP. The present study's primary purpose was to determine whether NSCLBP patients presented with higher lumbar muscle fatigability and fatigability asymmetry than asymptomatic participants. METHODS: Thirty NSCLBP patients and 23 asymptomatic participants performed the Sorensen test. The median frequencies from the electromyographs of the right and left erector spinae longissimus (ESL) and lumbar multifidus (LMF) were measured during the test. A linear regression was performed on the median frequencies on each muscle. Slope and initial median frequency were extracted to characterize fatigability. Asymmetry was quantified by the absolute differences between right-side and left-side muscle pairs. RESULTS: NSCLBP patients presented significantly poorer back extensor muscle endurance than asymptomatic participants. No differences were found between NSCLBP patients and asymptomatic participants in terms of fatigability or fatigability asymmetry for either the ESL or LMF. The initial median frequency in both muscles was significantly lower among NSCLBP patients. CONCLUSIONS: The present study showed that NSCLBP patients did not present higher fatigability or higher fatigability asymmetry in lumbar muscles than asymptomatic participants. The heterogeneity of the NSCLBP population, due to the absence of any specific etiology, may explain these findings. These slides can be retrieved under Electronic Supplementary Material.

Radiation-free measurement tools to evaluate sagittal parameters in AIS patients: a reliability and validity study.

PURPOSE: This study aimed to evaluate the intra-rater reliability and validity in comparison with the two-dimensional radiography (XR) of inclinometer (INCL) and rasterstereography (RAST) for assessing spinal sagittal angles of AIS patients. METHODS: Fifty-one AIS patients (13.5 (2.0) years, girls = 32 (63%), Cobb angle = 23.0 (17.4)°) were included in this study. Three repeated measurements of thoracic kyphosis (TK) and lumbar lordosis (LL) were evaluated using the INCL and RAST by the same operator on the same day of the XR examination. Intraclass correlation coefficients (ICC) were used to evaluate the reliability of the INCL and RAST systems. Additionally, Pearson coefficients were computed between the XR and INCL systems and between the XR and RAST systems. RESULTS: Reliability of each radiation-free system was excellent (ICC > 0.75 for INCL and RAST) for both the TK and LL parameters. The Pearson coefficients between each of the radiation-free systems and the XR were high to moderate for the TK (0.50 < RTK < 0.75 for INCL and RAST), high to moderate for the LL as measured with the RAST (0.50 < RLL < 0.75 for RAST) and low for the LL as measured with the INCL (RLL < 0.50 for INCL). CONCLUSION: This study demonstrated that for the RAST and INCL in AIS patients, there was (1) an excellent reliability for the TK and LL, (2) a high-to-moderate validity for measuring the TK and (3) a moderate and low validity for measuring the LL, respectively. These radiation-free systems could be used for the clinical follow-up of AIS patients for the evaluation of the TK. These slides can be retrieved under Electronic Supplementary Material.

Correction to: Locomotion and cadence detection using a single trunk-fixed accelerometer: validity for children with cerebral palsy in daily life-like conditions.

The original article [1] contained a minor error whereby the middle initial of Christopher J. Newman's name was mistakenly omitted.

Locomotion and cadence detection using a single trunk-fixed accelerometer: validity for children with cerebral palsy in daily life-like conditions.

BACKGROUND: Physical therapy interventions for ambulatory youth with cerebral palsy (CP) often focus on activity-based strategies to promote functional mobility and participation in physical activity. The use of activity monitors validated for this population could help to design effective personalized interventions by providing reliable outcome measures. The objective of this study was to devise a single-sensor based algorithm for locomotion and cadence detection, robust to atypical gait patterns of children with CP in the real-life like monitoring conditions. METHODS: Study included 15 children with CP, classified according to Gross Motor Function Classification System (GMFCS) between levels I and III, and 11 age-matched typically developing (TD). Six IMU devices were fixed on participant's trunk (chest and low back/L5), thighs, and shanks. IMUs on trunk were independently used for development of algorithm, whereas the ensemble of devices on lower limbs were used as reference system. Data was collected according to a semi-structured protocol, and included typical daily-life activities performed indoor and outdoor. The algorithm was based on detection of peaks associated to heel-strike events, identified from the norm of trunk acceleration signals, and included several processing stages such as peak enhancement and selection of the steps-related peaks using heuristic decision rules. Cadence was estimated using time- and frequency-domain approaches. Performance metrics were sensitivity, specificity, precision, error, intra-class correlation coefficient, and Bland-Altman analysis. RESULTS: According to GMFCS, CP children were classified as GMFCS I (n = 7), GMFCS II (n = 3) and GMFCS III (n = 5). Mean values of sensitivity, specificity and precision for locomotion detection ranged between 0.93-0.98, 0.92-0.97 and 0.86-0.98 for TD, CP-GMFCS I and CP-GMFCS II-III groups, respectively. Mean values of absolute error for cadence estimation (steps/min) were similar for both methods, and ranged between 0.51-0.88, 1.18-1.33 and 1.94-2.3 for TD, CP-GMFCS I and CP-GMFCS II-III groups, respectively. The standard deviation was higher in CP-GMFCS II-III group, the lower performances being explained by the high variability of atypical gait patterns. CONCLUSIONS: The algorithm demonstrated good performance when applied to a wide range of gait patterns, from normal to the pathological gait of highly affected children with CP using walking aids.

A Personalized Approach to Improve Walking Detection in Real-Life Settings: Application to Children with Cerebral Palsy.

Although many methods have been developed to detect walking by using body-worn inertial sensors, their performances decline when gait patterns become abnormal, as seen in children with cerebral palsy (CP). The aim of this study was to evaluate if fine-tuning an existing walking bouts (WB) detection algorithm by various thresholds, customized at the individual or group level, could improve WB detection in children with CP and typical development (TD). Twenty children (10 CP, 10 TD) wore 4 inertial sensors on their lower limbs during laboratory and out-laboratory assessments. Features extracted from the gyroscope signals recorded in the laboratory were used to tune thresholds of an existing walking detection algorithm for each participant (individual-based personalization: Indiv) or for each group (population-based customization: Pop). Out-of-laboratory recordings were analyzed for WB detection with three versions of the algorithm (i.e., original fixed thresholds and adapted thresholds based on the Indiv and Pop methods), and the results were compared against video reference data. The clinical impact was assessed by quantifying the effect of WB detection error on the estimated walking speed distribution. The two customized Indiv and Pop methods both improved WB detection (higher, sensitivity, accuracy and precision), with the individual-based personalization showing the best results. Comparison of walking speed distribution obtained with the best of the two methods showed a significant difference for 8 out of 20 participants. The personalized Indiv method excluded non-walking activities that were initially wrongly interpreted as extremely slow walking with the initial method using fixed thresholds. Customized methods, particularly individual-based personalization, appear more efficient to detect WB in daily-life settings.

Apathy in idiopathic normal pressure hydrocephalus: A marker of reversible gait disorders.

OBJECTIVE: Apathy-the most common behavioral disturbance in idiopathic normal pressure hydrocephalus (iNPH)-is associated with poor gait, but the role of apathy on gait improvement after cerebrospinal fluid (CSF) tapping has not been studied yet. This study aims to compare gait improvement after CSF tapping in iNPH patients with and without apathy. METHODS: Stride time variability (STV), a marker of higher level of gait control, was measured in 33 iNPH patients (78.4 ± 5.7 years; 36.4% women) with an optoelectronic system during usual walking (single task) and during walking while dual tasking of counting and verbal fluency before and 24 hours after CSF tapping. Apathy was defined by a score ≥14 on the Starkstein apathy scale. RESULTS: Apathy was present in 60.6% of patients. Cerebrospinal fluid tapping led to greater improvement of STV (ie, decrease) during dual-task walking (and more specifically categorical verbal fluency) in apathetic compared to nonapathetic patients (-44.7 ± 58.1% versus +4.24 ± 67.6%, respectively; P = .040), even after adjusting for age and depressive symptoms. More severe apathy was correlated with better STV improvement while dual tasking (categorical verbal fluency) after CSF tapping (r = -0.412; P-value = 0.021), while it was not correlated with improvement on executive tests. CONCLUSIONS: Our findings suggest that the presence of apathy is a predictor of better outcomes of gait disorders after CSF tapping in patients with iNPH.