Organ
Arachnoid granulations
Arachnoid projections associated with CSF outflow
High-yield
Granulations are part of the anatomy of CSF outflow, but drainage also involves pathways associated with cranial nerves and meningeal lymphatics.
Overview
Arachnoid granulations project toward dural venous spaces, often near the superior sagittal sinus and its lateral lacunae. They have traditionally been described as a route for cerebrospinal fluid to enter venous blood. Their structure and exact contribution to total drainage are more complex than a simple valve model.
Reference facts
- Location
- At the arachnoid–dura interface, including projections into venous sinuses and lateral lacunae, especially near the superior sagittal sinus
- Parts
- Microscopic arachnoid villi and larger granulations; size, shape and distribution change with age
- Blood supply
- Generally considered avascular, although rare capillaries have been demonstrated in the connective-tissue core of some granulations
- Function
- Associated with transfer of CSF toward venous and perisinus spaces; their share of total outflow remains under study
Clinical correlation
Subarachnoid bleeding or meningitis can impair CSF circulation and absorption, causing communicating hydrocephalus. This cannot always be reduced to scarring of granulations alone.
Frequently asked questions
Where are the arachnoid granulations located?
At the arachnoid–dura interface, including projections into venous sinuses and lateral lacunae, especially near the superior sagittal sinus.
What do the arachnoid granulations do?
Associated with transfer of CSF toward venous and perisinus spaces; their share of total outflow remains under study.
What are the parts of the arachnoid granulations?
Microscopic arachnoid villi and larger granulations; size, shape and distribution change with age.
What is the blood supply of the arachnoid granulations?
Generally considered avascular, although rare capillaries have been demonstrated in the connective-tissue core of some granulations.