Third ventricular width assessed by transcranial ultrasound correlates with cognitive performance in Parkinson's disease

Introduction: Cognitive impairment and dementia are common in PD; however, no stable marker of cognitive dysfunction is available. Transcranial sonography can evaluate global and focal brain atrophy and has been widely used in the differential diagnosis of parkinsonism. Methods: 225 consecutive PD patients were recruited in a two-center cross sectional study and underwent a standardized sonographic protocol assessing the third ventricle's width and substantia nigra hyperechogenicity. All subjects were evaluated with an extensive motor and cognitive battery. Results: 222 PD patients were included and classified as PD with normal cognition (PDNC; n = 130), mild cognitive impairment (PD-MCI; n = 61) and dementia (PDD; n = 31). Ventricular width correlated strongly with cognitive performance in all cognitive domains (p < 0.001) while SN size did not. PDD patients had significantly wider ventricles than PD patients without dementia (p < 0.001) while differences between PD-MCI and PDNC or PDD were less strong (p < 0.05). There were no group differences in SN size. ROC analyses resulted in age-related cut-offs of third ventricular diameter for the prediction of PDD (6.0 and 7.5 mm for subjects < and ≥70 years of age, respectively). These cut-offs significantly differentiated PDD from PDNC (p < 0.001) and from all patients without dementia (PDNC + PD-MCI; p < 0.001). Conclusions: The third ventricular diameter correlated with cognitive performance in all domains and was able to differentiate PDD patients from those without dementia. Longitudinal studies are warranted to evaluate whether transcranial sonography could identify PD patients at risk for a rapid cognitive decline.