Subaraknoidal

Subaraknoidal (subarachnoid) space is the interval between the arachnoid mater and the pia mater that envelops the brain and spinal cord. It is filled with cerebrospinal fluid (CSF) and contains major cerebral arteries and veins, protected by arachnoid trabeculae. The space forms cisterns around key brain structures, such as the interpeduncular, ambient, and cerebellomedullary cisterns, and is continuous with the spinal subarachnoid space.

Anatomically, the subaraknoidal space extends from the foramen magnum to the caudal end of the dural sac, which typically ends around the level of the second sacral vertebra in adults. CSF circulates through this space, delivering nutrients and removing waste. It is produced mainly by the choroid plexus, flows from the ventricles into the subarachnoid space via the foramina of Luschka and Magendie, and is reabsorbed into the venous system through arachnoid granulations into the dural venous sinuses, maintaining intracranial pressure and cushioning the brain and spinal cord.

Clinically important conditions involve the subarachnoid space. Subarachnoid hemorrhage results from rupture of intracranial aneurysms or trauma and is detected by imaging and CSF analysis. Meningeal infections such as meningitis involve this space, affecting CSF composition. Diagnostic procedures include lumbar puncture to sample CSF and CT imaging for acute hemorrhage, with findings such as red blood cells or xanthochromia guiding diagnosis.