subarachnoïdale

Subarachnoïdale refers to the subarachnoid space, the potential space between the arachnoid mater and the pia mater that surrounds the brain and spinal cord. This space contains cerebrospinal fluid (CSF), blood vessels of the central nervous system, and arachnoid trabeculations that span the gap between the two membranes. It is continuous around the brain and spinal cord and communicates with the ventricular system via the foramina of Luschka and Magendie, allowing CSF to circulate between the ventricles and the subarachnoid space. CSF is produced mainly by the choroid plexus in the ventricles, circulates through the ventricular system, enters the subarachnoid space, and is largely reabsorbed into the venous system via arachnoid granulations into the dural venous sinuses, such as the superior sagittal sinus.

Anatomically, the subarachnoid space contains cisterns, such as the interpeduncular and prepontine cisterns, where CSF pools. Arachnoid trabeculations connect the pia and arachnoid layers, helping to suspend the brain within CSF. Functionally, the subarachnoid space provides buoyancy for the brain, cushions neural tissue against trauma, maintains chemical stability, and serves as a conduit for immune surveillance and exchange of solutes.

Clinically, subarachnoid hemorrhage (SAH) is bleeding into this space, most often from rupture of a cerebral aneurysm or trauma, presenting with a sudden, severe headache and possible neck stiffness. Diagnosis typically involves noncontrast CT, with lumbar puncture if needed to detect xanthochromia. The subarachnoid space is also involved in infections such as meningitis and in diagnostic or therapeutic lumbar punctures and intrathecal drug delivery, as well as spinal anesthesia procedures.