Uncovering clinical and radiological asymmetry in progressive supranuclear palsy—Richardson’s syndrome

Background Richardson’s syndrome (RS) is considered the most symmetric phenotype of progressive supranuclear palsy (PSP) as opposed to PSP with predominant corticobasal syndrome (PSP-CBS) or parkinsonism (PSP-P). Objectives Evaluate asymmetrical motor and higher cortical features in probable PSP-RS and compare the degree of asymmetry of cortical lobes and hemispheres between PSP-RS, PSP-CBS, PSP-P, and age-matched healthy controls (HC). Methods Asymmetry of motor and higher cortical features evaluated with an extensive videotaped neurologic examination was investigated in 28 PSP-RS, 8 PSP-CBS, and 14 PSP-P. Brain MRI to compute the laterality index (LI) was performed in 36 patients as well as in 56 HC. Results In PSP-RS, parkinsonism was the most common asymmetric motor feature (53.6%), followed by dystonia and myoclonus (21.4% and 17.9%, respectively). Among higher cortical features, limb apraxia was found asymmetric in about one-third of patients. PSP-RS disclosed higher LI for hemispheres compared to HC, indicating a greater degree of asymmetry ( p = 0.003). The degree of asymmetry of clinical features was not different between PSP-RS and those qualifying for PSP-CBS or PSP-P. As for imaging, LI was not different between PSP-RS, PSP-CBS, and PSP-P in any cortical region. Conclusions Motor and higher cortical features are asymmetric in up to 50% of PSP-RS who also present a greater degree of asymmetry in hemispheres compared to age-matched HC. Lateralization of clinical features should be annotated in PSP.