The Potential Connection between the Brain and Neck: Exploring the Meningeal-Cervical Lymphatic Pathway in Primate...

Area of Science:

• Neuroscience
• Immunology
• Anatomy

Background:

• The brain's lymphatic drainage system is a rapidly evolving field of study.
• Historically, the brain was considered immune-privileged and lacking lymphatic vessels.
• Recent research suggests cerebrospinal fluid (CSF) and waste products may drain via meningeal lymphatics to deep cervical lymph nodes (dcLN).

Purpose of the Study:

• To investigate the in vivo evidence of a functional meningeal lymphatic pathway in non-human primates.
• To determine if cerebrospinal fluid (CSF) can be drained via the deep cervical lymph nodes (dcLN).

Main Methods:

• Two Macaca fascicularis non-human primates (NHPs) underwent craniotomy.
• A catheter was inserted into the subarachnoid space for indocyanine green (ICG) injection.
• Near-infrared (NIR) imaging tracked the distribution of ICG.

Main Results:

• Indocyanine green (ICG) was successfully detected in the peri-jugular deep cervical lymph nodes (dcLN) in both subjects.
• Drainage to the dcLN was observed within an average of 613.5 seconds post-intracranial injection.

Conclusions:

• This study presents the first in vivo primate evidence of meningeal lymphatic drainage to the dcLN.
• The findings support the anatomical and functional significance of this pathway in primates.
• The deep cervical lymph nodes (dcLN) may play a crucial role in clearing neuropathological proteins, with potential implications for Alzheimer's Disease.
• The use of indocyanine green (ICG) highlights its translational potential for future human studies.