Abstract
Increasing interest in rodent models for movement disorders has led to an increasing need for more accurate and precise methods for both delineating the nature of abnormal movements and measuring their severity. These studies describe application of simultaneous high-speed video kinematics with multichannel electromyography (EMG) to characterize the movement disorder exhibited by tottering mutant mice. These mice provide a uniquely valuable model, because they exhibit paroxysmal dystonia superimposed on mild baseline ataxia, permitting the examination of these two different problems within the same animals. At baseline with mild ataxia, the mutants exhibited poorly coordinated movements with increased variation of stance and swing times, and slower spontaneous walking velocities. The corresponding EMG showed reduced mean amplitudes of biceps femoris and vastus lateralis, and poorly modulated EMG activities during the step cycle. Attacks of paroxysmal dystonia were preceded by trains of EMG bursts with doublets and triplets simultaneously in the biceps femoris and vastus lateralis followed by more sustained coactivation. These EMG characteristics are consistent with the clinical phenomenology of the motor phenotype of tottering mice as a baseline of mild ataxia with intermittent attacks of paroxysmal dystonia. The EMG characteristics of ataxia and dystonia in the tottering mice also are consistent with EMG studies of other ataxic or dystonic animals and humans. These studies provide insights into how these methods can be used for delineating movement disorders in mice and for how they may be compared with similar disorders of humans.