Quantification of gait in mitochondrial m.3243A > G patients: a validation study

The Role of Movement Analysis in Diagnosing and Monitoring Neurodegenerative Conditions: Insights from Gait and Postural Control

Quantifying gait and postural control adds valuable information that aids in understanding neurological conditions where motor symptoms predominate and cause considerable functional impairment. Disease-specific clinical scales exist; however, they are often susceptible to subjectivity, and can lack sensitivity when identifying subtle gait and postural impairments in prodromal cohorts and longitudinally to document disease progression. Numerous devices are available to objectively quantify a range of measurement outcomes pertaining to gait and postural control; however, efforts are required to standardise and harmonise approaches that are specific to the neurological condition and clinical assessment. Tools are urgently needed that address a number of unmet needs in neurological practice. Namely, these include timely and accurate diagnosis; disease stratification; risk prediction; tracking disease progression; and decision making for intervention optimisation and maximising therapeutic response (such as medication selection, disease staging, and targeted support). Using some recent examples of research across a range of relevant neurological conditions-including Parkinson's disease, ataxia, and dementia-we will illustrate evidence that supports progress against these unmet clinical needs. We summarise the novel 'big data' approaches that utilise data mining and machine learning techniques to improve disease classification and risk prediction, and conclude with recommendations for future direction.

The KHENERGY Study: Safety and Efficacy of KH176 in Mitochondrial m.3243A>G Spectrum Disorders

KH176 is a potent intracellular reduction-oxidation-modulating compound developed to treat mitochondrial disease. We studied tolerability, safety, pharmacokinetics, pharmacodynamics, and efficacy of twice daily oral 100 mg KH176 for 28 days in a double-blind, randomized, placebo-controlled, two-way crossover phase IIA study in 18 adult m.3243A>G patients without cardiovascular involvement. Efficacy parameters included clinical and functional outcome measures and biomarkers. The trial was registered within ClinicalTrials.gov (NCT02909400), the European Clinical Trials Database (2016-001696-79), and ISRCTN (43372293) (The KHENERGY study). Twice daily oral 100 mg KH176 was well tolerated and appeared safe. No serious treatment-emergent adverse events were reported. No significant improvements in gait parameters or other outcome measures were obtained, except for a positive effect on alertness and mood, although a coincidence due to multiplicity cannot be ignored. The results of the study provide first data on safety and efficacy of KH176 in patients with mitochondrial disease and will be instrumental in designing future clinical trials.

Quantification of gait in children with mitochondrial disease

Mitochondrial disorders are multisystem conditions that can potentially affect gait in many ways. The aim of this study was to select the optimal protocol to quantify the spatiotemporal parameters of gait in ambulatory children with mitochondrial disorders based on feasibility, test-retest reliability, and the difference between patients and controls. Gait at self-selected pace was quantified in ambulatory children with a genetically confirmed primary mitochondrial disease using the GAITRite electronic walkway. Three protocols were tested: pre-exercise, post-exercise (after a 3-min walking test), and recovery. In 14 ambulatory patients, we showed good to perfect reliability for velocity, cadence, step length, step time, step time variability, and step width in the recovery condition. The difference between patients and 70 individually age- and gender matched healthy controls only became apparent in the post-exercise protocol. In conclusion, measuring spatiotemporal parameters of gait using the GAITRite in ambulatory children with mitochondrial disease is feasible and reliable for most of the parameters measured. When using gait analysis in future studies in children with mitochondrial disease, we advise i) to use an exercise test prior to the gait analysis, ii) to let children practice the test before the actual data collection, and iii) not to use symmetry parameters.

Feeding difficulties, a key feature of the Drosophila NDUFS4 mitochondrial disease model

Mitochondrial diseases are associated with a wide variety of clinical symptoms and variable degrees of severity. Patients with such diseases generally have a poor prognosis and often an early fatal disease outcome. With an incidence of 1 in 5000 live births and no curative treatments available, relevant animal models to evaluate new therapeutic regimes for mitochondrial diseases are urgently needed. By knocking down ND-18, the unique Drosophila ortholog of NDUFS4, an accessory subunit of the NADH:ubiquinone oxidoreductase (Complex I), we developed and characterized several dNDUFS4 models that recapitulate key features of mitochondrial disease. Like in humans, the dNDUFS4 KD flies display severe feeding difficulties, an aspect of mitochondrial disorders that has so far been largely ignored in animal models. The impact of this finding, and an approach to overcome it, will be discussed in the context of interpreting disease model characterization and intervention studies.This article has an associated First Person interview with the first author of the paper.