Effects of Sound Interventions on the Permeability of the Blood-Brain Barrier and Meningeal Lymphatic Clearance

Abstract

The meningeal lymphatic, or glymphatic, system is receiving increasing attention from the scientific community. Recent work includes noninvasive techniques to demonstrate relationships between blood-brain barrier (BBB) activity and the glymphatic system in the human central nervous system. One potential technique is the use of music/sound to enhance BBB permeability regarding the movement of small molecules in and out of the brain. However, there is minimal knowledge regarding the methodical investigation(s) of the uses of music/sound on BBB permeability and glymphatic clearance and the outcomes of these investigation(s). This review contains evidence discussing relationships between music/sound, BBB permeability, and meningeal lymphatic clearance. An overview of the anatomy and physiology of the system is presented. We discuss the uses of music/sound to modulate brain and body functions, highlighting music's effects on mood and autonomic, cognitive, and neuronal function. We also propose implications for follow-up work. The results showed that music and sound interventions do, in fact, contribute to the opening of the BBB and subsequently increase the function of the meningeal lymphatic system. Evidence also suggests that music/sound has the ability to reduce the collateral effects of brain injuries. Unfortunately, music/sound is rarely used in the clinical setting as a medical intervention. Still, recent research shows the potential positive impacts that music/sound could have on various organ systems.

Keywords: elimination; glymphatic system; meninges; music; noise; opening.

Figure 1

Glymphatic/Meningeal Lymphatic System Process. Illustration of the glymphatic/meningeal lymphatic system in terms of the cerebrospinal fluid (CSF) and the movement of solutes in and out of the brain. An expanded view is provided to allow for a better understanding of the process involved with the meningeal lymphatic vessels in reference to the blood–brain barrier and the flow of CSF. (A) Music/sound exposure in the scope of brain structure in terms of the CSF as paravascular influx is involved in the meningeal lymphatic system exchange from arteries to veins. A deep cervical lymph node representation is shown in which meningeal lymphatic vessels originate from within the neck. Nodes are involved with waste elimination based on lymph flow and perivenous efflux pathways. (B) A zoomed-in representation of brain meninges in which the meningeal lymphatic vessels are located in the subarachnoid space containing the CSF. A clear separation of meningeal lymphatic anatomy and its process is depicted compared to its counterpart, the glymphatic system residing in vessels in the brain tissue, as shown in panel C. (C) A zoomed-in representation of the glymphatic system based on the perivascular space in brain tissue. Brain circulation in terms of periarterial influx and perivenous efflux provides a pathway for solute waste clearance. The pia mater layer is tied with astrocytes and aquaporin-4 channels (AQP4). CSF influx through periarterial space into arteries allows AQP4 water pump function to drive CSF/interstitial fluid (ISF) exchange within the brain parenchyma. The convective flow of CSF/ISF exchange drives interstitial solutes through opposite AQP4 channels and through paravenous spaces into venous vessels as efflux essentially clears solutes/waste from the brain.

Figure 2

Relationship between music/sound exposure on meningeal lymphatic system/glymphatic system and blood–brain barrier function. The illustration depicts important outcomes that arise from music/sound exposure on the meningeal lymphatic/glymphatic system. The bullets emphasize the main points of these studies and this review.