The glymphatic pathway in neurological disorders.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing preclinical mechanisms and early observational human imaging studies.
PubMed 30353860 · doi:10.1016/S1474-4422(18)30318-1
What was done
Narrative review evaluating the anatomical and physiological characteristics of the glial-lymphatic (glymphatic) fluid-clearance pathway originally identified in rodents, and assessing translational imaging evidence in human neurological disorders including Alzheimer's disease, traumatic brain injury, stroke, and normal pressure hydrocephalus.
What was found
Rodent models demonstrate a two-fold increase in amyloid-beta clearance during sleep compared with waking, facilitated by aquaporin 4 (AQP4) water channels. In humans, intrathecal contrast MRI demonstrates CSF pathways resembling rodent glymphatic flow. PET studies demonstrate that one night of sleep deprivation leads to amyloid-beta accumulation in healthy brains, and patients with Alzheimer's disease exhibit reduced CSF clearance of amyloid-beta and tau tracers associated with grey-matter amyloid accumulation and altered AQP4 expression. No specific sample sizes, statistical values, or effect estimates are provided in the abstract.
Why it matters
Synthesizes mechanistic and early clinical neuroimaging data supporting sleep-dependent interstitial solute clearance as a potential pathophysiological contributor and therapeutic target in neurodegenerative and acute neurological diseases.
Limits
The paper is an unsystematic narrative review. Much of the mechanistic detail derives from rodent models, and human data are limited to cross-sectional neuroimaging and post-mortem tissue analyses, which cannot establish whether impaired glymphatic clearance is a cause or consequence of neurological pathology.
Cited by
- supports The glymphatic system is a primary mechanism by which the brain clears amyloid-beta plaques.