A Systematic Review of MRI Studies of the Cholinergic System in Lewy Body Diseases
Yiwei Hang1, Lucy Jin1, Christopher Tan1, Atif Niaz2, Ahmed Negida3, Matthew Barrett3
1VCU School of Medicine, 2Eastern Virginia Medical School, 3Department of Neurology at VCU
Objective:
To review the primary findings of MRI-based neuroimaging studies of cholinergic regions in the central nervous system in Lewy body diseases (LBD).
Background:
LBD encompass a spectrum of neurodegenerative disorders including isolated REM sleep behavior disorder (RBD), Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Degeneration of cholinergic neurons in the basal forebrain (BF) and upper brainstem, specifically the pedunculopontine nucleus (PPN), is a feature of LBD. Advances in MRI imaging have facilitated the investigation of the role of cholinergic degeneration in LBD.
Design/Methods:
Initial literature search was conducted on OVID platform based on PICO format: patients with LBD (Patient), MRI analysis of the cholinergic system (Intervention), and evidence of cholinergic system degeneration or dysfunction (Outcome). Conference abstracts, review articles, and duplicate results or publications were excluded. Subsequent articles were retrieved for full-text review.
Results:
This systematic review included 40 MRI studies of the BF and 16 studies of the PPN. The most common patient population studied was PD and the most common MRI modality investigated was T1 sequence. Reduced grey matter volume in the nucleus basalis of Meynert, a subregion of the BF, is associated with a range of clinical symptoms in LBD including cognitive impairment, visual hallucinations, mood disorders and gait impairment. Altered PPN structural connectivity to the supplemental motor area and cerebellum is implicated in postural instability and freezing of gait in PD patients, respectively.
Conclusions:
MRI-based neuroimaging studies add to the body of evidence that cholinergic degeneration plays an important role in the manifestations of LBD. Understanding how structural and connectivity changes in the BF and PPN contribute to the manifestations of LBD can potentially help guide future targeted therapies.