Abstract
Agreement among experienced clinicians is poor when assessing the presence and severity of ataxia, especially when signs are mild. Consequently, objective gait measurements might be beneficial for assessment of horses with neurological diseases. To assess diagnostic criteria using motion capture to measure variability in spatial gait-characteristics and swing duration derived from ataxic and non-ataxic horses, and to assess if variability increases with blindfolding. Cross-sectional. A total of 21 horses underwent measurements in a gait laboratory and live neurological grading by multiple raters. In the gait laboratory, the horses were made to walk across a runway surrounded by a 12-camera motion capture system with a sample frequency of 240Hz. They were made to walk normally and with a blindfold in at least three trials each. Displacements of reflective markers on head, fetlock, hoof, fourth lumbar vertebra, tuber coxae and sacrum derived from three to four consecutive strides were processed and descriptive statistics, receiver operator characteristics (ROC) to determine the diagnostic sensitivity, specificity and area under the curve (AUC), and correlation between median ataxia grade and gait parameters were determined. For horses with a median ataxia grade ≥2, coefficient of variation for the location of maximum vertical displacement of pelvic and thoracic distal limbs generated good diagnostic yield. The hoofs of the thoracic limbs yielded an AUC of 0.81 with 64% sensitivity and 90% specificity. Blindfolding exacerbated the variation for ataxic horses compared to non-ataxic horses with the hoof marker having an AUC of 0.89 with 82% sensitivity and 90% specificity. The low number of consecutive strides per horse obtained with motion capture could decrease diagnostic utility. Motion capture can objectively aid the assessment of horses with ataxia. Furthermore, blindfolding increases variation in distal pelvic limb kinematics making it a useful clinical tool.
Highlights
Ataxia is often recognised clinically as an irregularly irregular gait [1] and ataxia can be defined as an interruption in the phase-dependent cyclical relationship between body segments in both spatial and temporal domains [2]
Horses Horses were recruited from three sources: Group 1 included research horses with no known history of gait abnormalities that were purchased for an unrelated study of recurrent laryngeal neuropathy; Group 2 comprised horses referred to the Royal Veterinary College’s Equine Referral Hospital (ERH) for neurologic evaluation of gait deficits
Horses were recruited to Group 3 if a decision for euthanasia had been made in first opinion practice because of perceived moderate to severe ataxia
Summary
Ataxia is often recognised clinically as an irregularly irregular gait [1] and ataxia can be defined as an interruption in the phase-dependent cyclical relationship between body segments in both spatial and temporal domains [2]. The diagnostic workup is based on a thorough clinical and systematic neurological examination with neuroanatomical localisation [4]. This is followed, when appropriate, by laboratory testing of blood and cerebrospinal fluid [5], diagnostic imaging [6] and electrophysiologic examinations [7,8]. Cross-correlation of hoof motion pattern [10] and fuzzy clustering of motion capture signals [11] have been applied to ataxic horses walking and trotting on a treadmill. These techniques allow for discrimination between groups, but they have not been used diagnostically. Treadmill use in the assessment of ataxia is problematic: instead, over-ground gait analysis, might be preferable
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