Brain Glymphatic/Lymphatic Imaging by MRI and PET

Area of Science:

• Neuroscience
• Medical Imaging
• Anatomy

Background:

• The glymphatic system and meningeal lymphatics are crucial for brain fluid dynamics.
• Advanced imaging techniques like MRI and PET have enabled investigation of these systems.
• Previous studies primarily focused on rodent models, with limited understanding of human physiology.

Purpose of the Study:

• To compare brain fluid dynamics and lymphatic pathways in rodents and humans.
• To highlight the utility of intrathecal contrast-enhanced MRI in visualizing these pathways.
• To propose future imaging strategies for studying glymphatic/lymphatic roles in disease.

Main Methods:

• Intrathecal contrast-enhanced MRI in rodents and humans.
• Review of ex vivo fluorescent microscopy and in vivo two-photon imaging data.
• Analysis of cerebrospinal fluid (CSF) and interstitial fluid (ISF) dynamics.

Main Results:

• Humans primarily utilize dorsal meningeal lymphatic pathways for ISF-CSF-lymphatic efflux, unlike rodents.
• CSF to lymphatic efflux occurs across the arachnoid barrier over the dorsal dura in both species.
• Meningeal lymphatic efflux to cervical lymph nodes is well-delineated in humans via MRI.

Conclusions:

• Human and rodent glymphatic-lymphatic systems exhibit distinct anatomical pathways.
• Sleep and anesthesia significantly confound glymphatic/lymphatic flow interpretations in rodents.
• Non-invasive intrathecal SPECT/PET or MRI studies are proposed for future research into brain glymphatic/lymphatic roles in diseases.