Substantia Innominata: Atrophy, Gait Variability and Dual-Task Gait Across the Lewy Body Disease Spectrum

Abstract

Background: In Parkinson’s disease (PD) and dementia with Lewy bodies (DLB), the cholinergic system has been implicated in cognitive and gait decline. The nucleus basalis of Meynert (NBM), within the substantia innominata (SI), is the main cholinergic nucleus projecting to the cortex. In this study, the relationship between atrophy of the SI on cognitive phenotypes and quantitative gait performance was evaluated in relation to gray matter (GM) volume.

Methods: Ninety-nine participants – 20 control, 42 PD with normal cognition (PD-NC), 19 PD with mild cognitive impairment (PD-MCI) and 18 PD dementia or DLB patients (PDD/DLB) – were examined. Measures included Montreal Cognitive Assessment (MoCA) score, motor symptom severity, quantitative gait analysis measures and dual-task cost (DTC) to gait speed. Manual measurement of SI volume was performed on T1 MRI scans; automated methods were used for GM volumes. The relationships between gait changes, volumetric imaging and clinical measures were assessed.

Results: Smaller SI volumes were seen in PD-MCI and PDD/DLB subjects adjusting for age. SI and GM atrophy were both associated with greater step length variability, and GM was associated with increased DTC to gait speed. These were not significant after adjusting for the false discovery rate. Lower MoCA score was associated with impairments in gait speed, DTC to gait speed and gait variability.

Conclusion: The SI was associated with cognitive impairment in participants with Lewy body diseases. However, more widespread cortical atrophy may be better related to selected cognitive aspects of gait (DTC to gait speed with animal fluency).