Objective: The aim of this study is the development of a new kinematic model for cervical spine to assess abnormal head and neck postures and movements in CD patients.

Background: Cervical dystonia (CD) is a movement disorder characterized by involuntary neck muscle contractions causing abnormal postures and movements and poor motor control with a negative impact on the quality of life. Current  assessment is mainly clinical [1], and TWSTRS (Toronto Western Spasmodic Torticollis Rating Scale) is often used. Kinematic analysis can give precise quantitative data of abnormal movement. Only few studies about kinematic models has been suggested [2].

Methods: 14 healthy subjects (HS, mean age 49 ± 16,6 years) and 10 CD patients (CD, 53 ± 13,1 years) were analyzed in association with TWSTRS. The protocol evaluates posture at rest and during movements of the head and neck with open and closed eyes. An optoelectronic system (Smart, BTS , Milan) with 9 TV Cameras was used. A biomechanical model with 15 markers placed on specific anatomical landmarks of the head, trunk and upper limbs was created to evaluate absolute and relative movements. A synthetic index which takes into account the deviations in the 3 planes of space in relation with the head position was defined at rest with eyes closed (Global_Rest_EC) and open (Global_Rest_EO) and during rotation to controlateral side of dystonia (Global_Rot). A comparison between HS and CD was performed with Mann-Whitney U test.

Results: Data analysis showed a HS Global_restEC average of 8.10 ° (SD = 5,9) and a CD Global_restEC average of 24.8 ° (SD = 17.3), with statistically significant difference between the two groups (p = 0.016), as well as in Global_restEO (p> 0.01) with a mean value of HS of 9.15 ° (SD = 4.5) and CD 24.1 ° (SD = 17.4). In Global_Rot the average of the two groups is respectively of 0.88 (SD = 0.07) for HS and 0.70 (SD = 0.14) for CD; this is also statistically significant (p <0.01). No significant correlation was found between TWSTRS and Global_Rot index.

Conclusions: These indexes can be useful for a quantitative analysis of the pathological head and neck postures and movements in the 3 planes of the space in CD patients. This model can objectively analyze clinical changes  before and after pharmacological and rehabilitative treatments. 

References: [1] Albanese A, et al. Phenomenology and Classification of Dystonia: A Consensus Update, Mov Disord 2013; 28(7):874-83.

[2] Boccagni C, et al. Motion analysis in cervical dystonia, Neurol Sci 2008; 29(6):375-81.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/development-of-a-new-kinematic-model-for-head-and-neck-movement-assessment-in-cervical-dystonia/