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Reliability and validity of a new Mouse Tic Severity Scale

Juan Pablo Beccaria

  • CABA,
  • Argentina
  • Juan Pablo Beccaria ¹
  • , Camila Coll ¹
  • , Murer Gustavo ¹
  • , Belforte Juan ¹
  • 1 GNS - IFIBIO Houssay - UBA - CONICET

Sudden, rapid, recurrent, non-rhythmic motor movements or vocalizations are the main medical sign of Tourette Syndrome (TS). Since their intensity and manifestation is exceedingly variable, tics are challenging to quantify. The Yale Global Tics Severity Scale (YGTSS) is perceived as the gold-standard clinical scale for tic quantification not only for TS but also for any other disorder that may present tics. YGTSS measures tic complexity, frequency, intensity and interference with normal behavior. In addition, since YGTSS is used world-wide, it provides comparable and reproducible data. However, there is no similar method for scoring tics in animal models. The present work aims to validate a mouse tic severity scale (MTSS) based on YGTSS standards. For that, we used a new murine model of TS developed in our lab, in which selective ablation of striatal Nkx2.1+ derived interneurons leads to exacerbated spontaneous repetitive behaviors including tic-like movements (See Coll et al. poster). High temporal resolution videos of lesioned and control mice were thoroughly watched and scored by two treatment-blinded observers. Lesioned mice showed a higher score than their control littermates both globally and in every scale section. Moreover, total punctuation and presence of particular patterns of movements correlated with lesion extent. These results suggest that MTSS might be a valid and reproducible scale to measure tics in mice.