EEG markers of cholinergic dysfunction in Lewy body diseases: A review.

BACKGROUND: Cholinergic dysfunction is common in Lewy body diseases and current symptomatic treatments aim to ameliorate the cholinergic deficits; however individual response is highly variable. Furthermore, future disease modifying therapies will likely target this system, highlighting the need for cholinergic biomarkers that can predict response to treatment and monitor change. EEG, a diagnostic and emerging prognostic biomarker, may offer an affordable, well-tolerated way to assess cholinergic function, though this link remains uncertain. This review synthesizes EEG findings in Lewy body diseases, focusing on its potential as a cholinergic marker. METHODS: PubMed was searched to identify publications involving Lewy body diseases, EEG and cholinergic system. Study abstracts were screened to include original English language research articles involving human EEG studies and another cholinergic biomarker or medication related to the cholinergic system. RESULTS: Eleven studies evaluated the use of EEG in Lewy body diseases: seven studies used EEG in combination with other cholinergic biomarkers, and four evaluated EEG changes related to cholinesterase inhibitor use. Promising cholinergic EEG biomarkers include reduced alpha reactivity and dominant frequency slowing. Additionally, alterations in specific band power, higher frequency functional connectivity and an acetylcholine EEG index (based on statistical pattern recognition) have also been related to cholinergic dysfunction. CONCLUSION: This review shows EEG is a promising non-invasive biomarker which is sensitive to cholinergic dysfunction in Lewy body diseases. Future research is required to verify the specificity of EEG cholinergic biomarkers against other modalities, clarify mechanisms of neurophysiological alterations, and enable their integration into clinical trials.