Space
Subarachnoid space
The CSF compartment between arachnoid and pia
High-yield
The compartment contains CSF, major surface vessels and portions of nerve roots. It continues through the foramen magnum into the spinal canal and typically reaches approximately S2. The spinal epidural compartment is also a real anatomical space.
Overview
CSF occupies this real compartment around the brain and spinal cord. Arachnoid trabeculae cross between the outer arachnoid and inner pial surfaces. Where arachnoid bridges over the brain's contours, wider cisterns form, including the cerebellomedullary, prepontine, interpeduncular, chiasmatic and quadrigeminal cisterns.
Reference facts
- Boundaries
- Arachnoid externally and pia internally, with crossing trabeculae and locally expanded cisterns.
- Contents
- CSF, surface arteries and veins, and the cisternal portions of cranial nerves and spinal nerve roots; the cerebral arterial circle lies within basal cisterns.
- Communications
- Communicates with the fourth ventricle through its median and lateral apertures and with the spinal CSF compartment. CSF leaves through several pathways, including arachnoid projections and routes associated with nerves and meningeal lymphatics.
Clinical correlation
A ruptured intracranial aneurysm can release blood into the subarachnoid compartment. Sudden severe headache is a characteristic presentation; vomiting, neck stiffness or altered consciousness may accompany it, but the complete symptom set is not always present.
Frequently asked questions
What are the boundaries of the subarachnoid space?
The subarachnoid space is bounded by the arachnoid externally and pia internally, with crossing trabeculae and locally expanded cisterns.
What does the subarachnoid space contain?
CSF, surface arteries and veins, and the cisternal portions of cranial nerves and spinal nerve roots; the cerebral arterial circle lies within basal cisterns.
What does the subarachnoid space communicate with?
Communicates with the fourth ventricle through its median and lateral apertures and with the spinal CSF compartment. CSF leaves through several pathways, including arachnoid projections and routes associated with nerves and meningeal lymphatics.