Factor analysis and clustering of motor and psychiatric dimensions in idiopathic blepharospasm

Introduction: Idiopathic blepharospasm is a clinically heterogeneous form of focal dystonia, also associated with psychiatric symptoms. The identification of the most relevant sets of motor and psychiatric manifestations may help better understand the specific phenomenology of the condition and delineate blepharospasm subtypes more accurately. Methods: Patients with idiopathic blepharospasm were from the Dystonia Coalition project. Factor analysis of several motor and psychiatric scales was performed to identify the relevant determinants of blepharospasm severity. The selected items were then used in a data-driven cluster analysis to subtype blepharospasm individuals. Results: Factor analysis reduced the many variables in the motor and psychiatric scales to 13 variables distributed in four factors. When the four sets were used as clustering variables, three blepharospasm clusters were identified: cluster 1 was characterized by low levels of motor and psychiatric factors; cluster 2 showed high levels of both motor and psychiatric factors; and cluster 3 showed high levels of psychiatric factors (similar to cluster 2) but low level of motor factors (similar to that of cluster 1). Conclusions: Factor analysis enabled the identification of key motor and psychiatric determinants of blepharospasm severity. The derived factor sets provide a streamlined tool for predicting and measuring these dimensions. This approach also facilitated more precise cluster analysis and improved recognition of clinical subtypes.