Definition

Noun: A specific anatomical compartment within the meninges, the protective membranes surrounding the brain and spinal cord. It is located between the arachnoid mater (the middle layer) and the pia mater (the innermost layer). This space is filled with cerebrospinal fluid (CSF), which cushions the central nervous system.

Usage

The term is used exclusively in anatomical, medical, and neurological contexts to describe this precise fluid-filled compartment. - The subarachnoid space is a critical area for the circulation of cerebrospinal fluid. - A hemorrhage into the subarachnoid space is a serious medical emergency. - The needle was carefully inserted to obtain a sample of fluid from the lumbar subarachnoid space.

Advanced Usage

• Lumbar subarachnoid space: Refers specifically to the portion of this space in the lower back, which is the site for a lumbar puncture (spinal tap) procedure.
  • During a spinal tap, cerebrospinal fluid is drawn from the lumbar subarachnoid space.
• Cisterns (subarachnoid cisterns): Expanded areas within the subarachnoid space where the arachnoid and pia mater are widely separated, creating larger pools of CSF.
  • The cerebellomedullary cistern is a major subarachnoid cistern.

Variants and Related Words

• Subarachnoid (adjective): Of or relating to the subarachnoid space.
  • Subarachnoid hemorrhage.
• Arachnoid mater (noun): The middle meningeal layer bordering the subarachnoid space.
• Pia mater (noun): The innermost meningeal layer bordering the subarachnoid space.
• Cerebrospinal fluid (CSF) (noun): The fluid contained within the subarachnoid space.

Synonyms

• Leptomeningeal space: A more technical synonym, as the arachnoid and pia mater together are called the leptomeninges.

Related Phrases

• Subarachnoid block: An obstruction to CSF flow within this space.
• Subarachnoid screw / bolt: A medical device sometimes placed to monitor pressure within this space.

Noun

1. a space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid