Obsessive-compulsive behavior as a symptom of dementia in progressive supranuclear palsy

Aims: To describe obsessive-compulsive symptoms (OCS) as under-recognized behavioral and psychological symptoms of dementia of progressive supranuclear palsy (PSP) and to discuss possible mechanisms based on MRI and SPECT findings. Methods: We studied 74 PSP patients. OCS are defined as persistent and unreasonable, but non-delusional/hallucinatory, ideas and behaviors. Demography, cognition, the widths of middle cerebellar peduncles (MCP) and the inter-caudate distances (ICD), both corrected by the intracranial size (MCP and ICD ratios), and changes on voxel-based SPECT were compared between the subgroups with and without OCS. Finally, the predicative power of various factors to OCS was investigated. Results: We observed OCS in 18 patients (24%). They were obsessed with daily trifles and physical symptoms among other things. OCS was not associated with demography or cognitive levels. OCS-positive patients had significantly smaller MCP and ICD ratios and showed marked uptake decreases in the orbitofrontal cortex, caudate and thalamus. Relative uptake increases in the cerebellum, specifically the tonsils, were milder in OCS-positive than -negative patients. A smaller right MCP, a smaller ICD ratio and lower uptake increases in the right cerebellar were the significant predictors of OCS. Conclusions: OCS are frequent but under-recognized behavioral and psychological symptoms of dementia in PSP. Dysfunction of the fronto-caudate-thalamus-cerebellum circuit may be involved.