Function of glymphatic system linked to disability progress in Parkinson’s disease

Key takeaways:

• Glymphatic clearance may be a reliable marker of longitudinal cognitive and motor decline in Parkinson’s.
• The DTI-ALPS index is a reliable indicator of Parkinson’s disease pathology.

ORLANDO, Fla. — Glymphatic function, as measured by an index of system clearance, is associated with rates of cognitive and motor decline as well as disability worsening in Parkinson’s disease, according to a poster.

“We know [Parkinson’s disease] is characterized by motor symptoms but there are some non-motor symptoms that are debilitating like cognitive function and sleep impairment, which we believe might be related to the glymphatic system,” Aya Miften, BA, a student at the University of Colorado Anschutz Medical Campus, told Healio.

Prior research has established the glymphatic system acts within the brain in a similar manner as the lymphatic system throughout the body, evacuating neurotoxic waste such as beta-amyloid, which is elevated in PD pathology, Miften and colleagues wrote.

The researchers evaluated the efficacy of a novel measure of glymphatic system clearance, diffusion tensor imaging along with perivascular space (DTI-ALPS), in those with PD compared with healthy controls, while also examining relationships between the index and longitudinal changes in cognition and PD symptom severity.

Their study included 32 individuals with PD and 23 healthy controls. Participants underwent baseline diffusion tensor imaging as well as a comprehensive cognitive battery consisting of 10 tests across five domains (attention, memory, executive function, language, visuospatial function, processing speed). Following these evaluations, symptomatic enrollees were classified as either having normal cognition (PD-NC) or mild cognitive impairment (PD-MCI)

A 21-person subgroup of those with PD returned for additional cognitive assessments as well as motor function measurement via the Movement Disorders Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) up to 4 years after the initial testing.

After the researchers applied the novel metric to each hemisphere of the brain for both participants diagnosed with PD and healthy controls, data showed that those with PD had lower ALPS compared with healthy participants; those with PD-MCI recorded lower ALPS compared with the PD-NC subgroup; and lower ALPS in both hemispheres were significant predictors of greater cognitive decline as well as higher MDS-UPRS scores across the 4 years of follow up.

Miften and colleagues also found that lower ALPS and longer disease duration were associated with cognitive decline for those with PD and lower ALPS was associated with worsening PD disease severity.

“This type of imaging technique could be used in the clinic as a way to predict possible decline cognitively along with motor symptoms as well,” Miften said. “Any interventions that are targeting glymphatic clearance directly, like when you sleep, or indirectly like exercise, should be explored.”