Objective: To establish a clear definition and axis classification scheme for tics that serves to separate phenomenology from etiology.

Background: Gilles de la Tourette documented abnormal movements and vocalizations that were distinct from previously described movement disorders. Over time, the criteria for Tourette syndrome have evolved, while the presence of tics remained an uncontested prerequisite. However, the true definition of tics has been challenging. The surge of functional tic-like presentations during the COVID-19 pandemic illuminated the need for greater clarity in the approach to tic classification. 

Commissioned by the MDS, The Task Force on Tic Disorders embarked on the mission of establishing a clear definition and classification scheme to promote a common vocabulary and rational approach to treatment, education and research.

Method: A panel was convened with two co-chairs and a selection of experts with extensive experience representing neurology, psychiatry, and psychology. Geographic diversity was incorporated to underscore the need for broad applicability. The project extended three years. The co-chairs met bi-weekly and the task force met monthly via Zoom and at the annual MDS Congress.   

The project’s milestones were: 1.) establishing the definition of tics, 2.) delineation of axes to distinguish phenomenology and etiology, and 3.) more granular work within the subsections of the classification axes. The committee sequentially reviewed historical accounts and existing literature, deliberated points of contention, and implemented serial modified Delphi-style voting and comment before final acceptance of classification schemes. There was a critical reappraisal of standard concepts, with emphasis on clarifying and improving the global approach to tic classification.

Results: We present the axis classification scheme in [Figure 1].  Axis 1a depicts Tics Phenomenology- output, topography, complexity, and associated features.  Axis 1b classifies Additional Clinical Features that help delineate the complete syndrome including age, evolution, agency and comorbidities.  Finally, Axis 2 addresses etiology, including idiopathic neurodevelopmental tics, tics within genetic syndromes, acquired, and functional tics.

Conclusion: The creation of a new classification scheme has the potential to improve care and communication, and to raise the quality of research through increasing specificity of tic terminology.

Figure 1

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mds-task-force-on-tic-disorders-development-of-a-new-classification-scheme-for-tic-disorders/