Abstract
Cerebrospinal fluid (CSF) flows through the brain, transporting chemical signals and removing waste. CSF production in the brain is balanced by a constant outflow of CSF, the anatomical basis of which is poorly understood. Here, we characterized the anatomy and physiological function of the CSF outflow pathway along the olfactory sensory nerves through the cribriform plate, and into the nasal epithelia. Chemical ablation of olfactory sensory nerves greatly reduced outflow of CSF through the cribriform plate. The reduction in CSF outflow did not cause an increase in intracranial pressure (ICP), consistent with an alteration in the pattern of CSF drainage or production. Our results suggest that damage to olfactory sensory neurons (such as from air pollution) could contribute to altered CSF turnover and flow, providing a potential mechanism for neurological diseases.
Highlights
The brain has a very high metabolic rate, but lacks a conventional lymphatic system for clearance of metabolites and waste products
Because the bone is impermeable to fluid movement, these holes will be the only outlet for cerebrospinal fluid (CSF) flow through the cribriform plate (CP), and the nature of the soft tissue filling them will play an important role in directing the flow of CSF
MicroCT imaging, physiology, and tracer dye injections, we investigated the anatomical basis of CSF outflow through the CP into the nasal cavity
Summary
The brain has a very high metabolic rate, but lacks a conventional lymphatic system for clearance of metabolites and waste products. The balance between CSF production and outflow plays a key role in setting and maintaining the intracranial pressure (ICP) (Kosteljanetz, 1987). Because CSF production is actively regulated to maintain normal ICP (Marmarou et al, 1975), damage to the outflow pathways could drive compensatory decreases in CSF production and turnover (Czosnyka et al, 2004) or altered patterns of CSF flow. Either of these could result in decreased waste clearance, as is seen in aging and some neurological diseases
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