Hold that pose: capturing cervical dystonia's head deviation severity from video.

OBJECTIVE: Deviated head posture is a defining characteristic of cervical dystonia (CD). Head posture severity is typically quantified with clinical rating scales such as the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Because clinical rating scales are inherently subjective, they are susceptible to variability that reduces their sensitivity as outcome measures. The variability could be circumvented with methods to measure CD head posture objectively. However, previously used objective methods require specialized equipment and have been limited to studies with a small number of cases. The objective of this study was to evaluate a novel software system-the Computational Motor Objective Rater (CMOR)-to quantify multi-axis directionality and severity of head posture in CD using only conventional video camera recordings. METHODS: CMOR is based on computer vision and machine learning technology that captures 3D head angle from video. We used CMOR to quantify the axial patterns and severity of predominant head posture in a retrospective, cross-sectional study of 185 patients with isolated CD recruited from 10 sites in the Dystonia Coalition. RESULTS: The predominant head posture involved more than one axis in 80.5% of patients and all three axes in 44.4%. CMOR's metrics for head posture severity correlated with severity ratings from movement disorders neurologists using both the TWSTRS-2 and an adapted version of the Global Dystonia Rating Scale (rho = 0.59-0.68, all p <0.001). CONCLUSIONS: CMOR's convergent validity with clinical rating scales and reliance upon only conventional video recordings supports its future potential for large scale multisite clinical trials.

Does Raising the Arms Modify Head Tremor Severity in Cervical Dystonia?

Background: A defining characteristic of dystonia is its position-dependence. In cervical dystonia (CD), sensory tricks ameliorate head tremor (HT). But it remains unknown whether raising the arms alone has the same impact. Methods: We analyzed data collected from patients enrolled by the Dystonia Coalition. For 120 patients with HT, we assessed how raising their arms without touching their head changed their HT severity. Results: Forty-eight out of 120 patients exhibited changes in HT severity when raising their arms. These patients were more likely to exhibit decreases in HT severity (N = 35) than increases (N = 13, χ2 (1, N = 48) = 10.1, p = 0.002). Demographic factors and sensory trick efficacy were not significant predictors of whether HT severity changed when raising their arms. Discussion: Raising the arms without touching the head is a posture that can reduce HT severity in some CD patients. Our results extend the concept of position-dependent motor symptoms in CD to include the position of the arms. Highlights: Head tremor (HT) is a prevalent symptom of cervical dystonia (CD) that can often be disabling. This study demonstrates that raising the arms without touching the head is a posture that can reduce HT severity in some CD patients. Our findings also identify a novel form of position-dependence in CD.

It's tricky: Rating alleviating maneuvers in cervical dystonia.

OBJECTIVES: To investigate hypothesized sources of error when quantifying the effect of the sensory trick in cervical dystonia (CD) with the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS-2), test strategies to mitigate them, and provide guidance for future research on the sensory trick. METHODS: Previous analyses suggested the sensory trick (or "alleviating maneuver", AM) item be removed from the TWSTRS-2 because of its poor clinimetric properties. We hypothesized three sources of clinimetric weakness for rating the AM: 1) whether patients were given sufficient time to demonstrate their AM; 2) whether patients' CD was sufficiently severe for detecting AM efficacy; and 3) whether raters were inadvertently rating the item in reverse of scale instructions. We tested these hypotheses with video recordings and TWSTRS-2 ratings by one "site rater" and a panel of five "video raters" for each of 185 Dystonia Coalition patients with isolated CD. RESULTS: Of 185 patients, 23 (12%) were not permitted sufficient testing time to exhibit an AM, 23 (12%) had baseline CD too mild to allow confident rating of AM effect, and 1 site- and 1 video-rater each rated the AM item with a reverse scoring convention. When these confounds were eliminated in step-wise fashion, the item's clinimetric properties improved. CONCLUSIONS: The AM's efficacy can contribute to measuring CD motor severity by addressing identified sources of error during its assessment and rating. Given the AM's sensitive diagnostic and potential pathophysiologic significance, we also provide guidance on modifications to how AMs can be assessed in future CD research.

Postural Directionality and Head Tremor in Cervical Dystonia.

Background: Although abnormal head and neck postures are defining features of cervical dystonia (CD), head tremor (HT) is also common. However, little is known about the relationship between abnormal postures and HT in CD. Methods: We analyzed clinical data and video recordings from 185 patients enrolled by the Dystonia Coalition. We calculated the likelihood of their HT and HT type ("regular" vs. "jerky") given directionality of abnormal head postures, disease duration, sex, and age. Results: Patients with retrocollis were more likely to have HT than patients with anterocollis (X2 (1, N = 121) = 7.98, p = 0.005). There was no difference in HT likelihood given left or right turning in laterocollis and rotation. Patients with HT had longer disease duration (t(183) = 2.27, p = 0.024). There was no difference in age between patients with and without HT. In a logistic regression model, anterocollis/retrocollis direction (X2 (1, N = 121) = 6.04, p = 0.014), disease duration (X2 (1, N = 121) = 7.28, p = 0.007), and the interaction term between age and disease duration (X2 (1, N = 121) = 7.77, p = 0.005) collectively contributed to HT likelihood. None of the postural directionality or demographic variables were associated with differential likelihood of having regular versus jerky HT. Discussion: We found that HT is more likely for CD patients with a specific directionality in their predominant posture. Our finding that CD patients with longer disease duration have a higher likelihood of HT also raises the question of whether HT becomes more likely over time in individual patients.

Sensory Tricks Are Associated with Higher Sleep-Related Quality of Life in Cervical Dystonia.

Background: Sensory tricks are compensatory gestures that cervical dystonia (CD) patients use to reduce abnormal neck posture and movements. Although sensory tricks are common in CD, little is known about whether trick efficacy changes over time or has effect on quality of life. Methods: We analyzed clinical data and video recordings from 188 patients with isolated CD. We calculated the duration of CD and assessed the Toronto Western Spasmodic Torticollis Rating Scales and the Cervical Dystonia Impact Profile (CDIP-58). Results: A longer duration of CD corresponded to a less effective sensory trick (r(187) = 0.1901, p = 0.009). Patients who demonstrated more effective sensory tricks reported higher sleep-related quality of life than patients with less effective sensory tricks (r(187) = 0.1680, p = 0.0212). There were no significant relationships between the effectiveness of a sensory trick and the other aspects of quality of life as measured by the CDIP-58. Discussion: Patients who have had CD longer had less effective sensory tricks consistent with patients' verbal reports of previously having a trick that no longer works. Patients should be apprised of a wide variety of sensory tricks because their previous tricks may lose efficacy over time and because more effective tricks are associated with higher sleep-related quality of life.