subarachnoidal

Subarachnoidal, typically written as subarachnoid in English, refers to the subarachnoid space, a potential space between the arachnoid mater and the pia mater that surrounds the brain and spinal cord. This space contains cerebrospinal fluid (CSF) and the major blood vessels, and it extends over the brain and down the spinal canal to the sacral region.

Anatomy and function: CSF is produced mainly by the choroid plexus within the ventricles and circulates through the ventricular system before entering the subarachnoid space via the foramina of Luschka and Magendie. Within the subarachnoid space, CSF bathes the brain and spinal cord, providing buoyancy, protection, and a medium for nutrient transport and waste removal. Absorption occurs through arachnoid granulations into venous sinuses.

Clinical relevance: The subarachnoid space is involved in several important conditions. Subarachnoid hemorrhage results from rupture of a blood vessel, often an intracranial aneurysm, and presents with a sudden, severe headache, neck stiffness, and sometimes loss of consciousness. Diagnosis typically starts with imaging (non‑contrast CT) and may include lumbar puncture if hemorrhage is suspected but not visible on CT. Meningitis or arachnoiditis involves inflammation or irritation of the meninges in the subarachnoid space, detectable by CSF analysis showing pleocytosis, elevated protein, and other markers.

Procedures: Lumbar puncture accesses the subarachnoid space to obtain CSF for analysis or therapeutic administration. Imaging and clinical assessment guide management, particularly when raised intracranial pressure or mass lesions are a concern. The term “subarachnoidal” is common in some languages and essentially equates to the English term “subarachnoid.”