Quantification of gait in dystonic Gunn rats

Spontaneously jaundiced Gunn rats exposed to sulfadimethoxine develop bilirubin encephalopathy (kernicterus) with hearing loss and dystonia, closely resembling the human syndrome. We recently characterized the electromyographic activity in this animal model supporting our clinical impression of dystonia. The objective of this study was to develop a simple, non-invasive method to quantify the motor deficits in dystonic rodents. On postnatal day 16, Gunn rats were treated with 100mg/kg of sulfadimethoxine or saline. On postnatal day 31, the ventral view of the animals was videotaped while the animals walked inside a Plexiglas chamber. Individual video frames were reviewed and specific gait parameters including hindlimb spread, step length ratio variability, stance/swing ratio and walking speed were compared between dystonic and non-dystonic jaundiced and non-jaundiced littermates. Data analysis demonstrated statistically significant increases in hindlimb spread and step length ratio variability and decreases in walking speed in dystonic animals as compared to controls. This study demonstrates a valuable technique to objectively characterize dystonia in Gunn rats, which could have wide use for other experimental movement disorders as well.