Neuroanatomical correlates of the progressive supranuclear palsy corticobasal syndrome hybrid

Background: The progressive supranuclear palsy syndrome (PSPS) and corticobasal syndrome (CBS) are associated with relatively specific patterns of atrophy; the former predominantly involving the brainstem, the latter frontoparietal regions. However, it has become apparent that there are subjects that meet criteria for PSPS and CBS. We refer to subjects with this presentation as Hybrids. The hybrid presentation is not rare, yet there are no studies that have assessed the neuroanatomical correlates of the hybrid syndrome to explain its occurrence. Method: In this study of 41 subjects and controls, we utilized the technique of voxel-based morphometry to assess both gray and white matter volume loss in six prospectively recruited Hybrids that underwent 3.0 T volumetric head magnetic resonance image scanning to determine the neuroanatomical correlates of the syndrome. We compared patterns of atrophy in three prospectively recruited groups: the Hybrid group (n = 6), a PSPS group (n = 10), and CBS group (n = 5). All 21 subjects had completed the same standardized batteries assessing cognition, and motor, behavioral, executive, oculomotor and limb praxis function. Results: The Hybrid group showed imaging features of both PSPS and CBS, with volume loss observed in the brainstem (superior cerebellar peduncle) and cortex (medial and lateral premotor, prefrontal and motor cortex). As expected, typical patterns of loss were observed in PSPS and CBS. Conclusions: These findings explain the neuroanatomical basis of the overlapping presenting signs and symptoms of PSPS and CBS, in Hybrids.