Arachnoid granulation

Arachnoid Granulations

Arachnoid granulations (pronounced: a-rack-noyd gran-u-lay-shuns), also known as Pacchionian bodies or Pacchionian granulations, are small protrusions of the arachnoid mater (the middle layer of the meninges) into the dural sinuses, which allow cerebrospinal fluid (CSF) to exit the subarachnoid space and enter the blood stream.

Etymology

The term "arachnoid" comes from the Greek word "arachne," meaning spider, and "oid," meaning like or similar to. This is due to the web-like appearance of the arachnoid mater. "Granulation" comes from the Latin word "granulum," which means small grain. These structures were first described by Italian anatomist Antonio Pacchioni in 1705, hence the alternative names "Pacchionian bodies" or "Pacchionian granulations."

Function

Arachnoid granulations act as one-way valves. Primarily, they are responsible for the transfer of cerebrospinal fluid from the subarachnoid space to the venous system. This process plays a crucial role in maintaining the balance of cerebrospinal fluid in the brain and spinal cord.

Clinical Significance

Arachnoid granulations can sometimes be mistaken for dural venous sinuses thrombosis or meningiomas (a type of brain tumor) on medical imaging. However, they are a normal part of the brain's anatomy and are typically harmless. In some cases, they can enlarge, particularly in older adults and people with increased intracranial pressure, a condition known as giant arachnoid granulation.

Related Terms

External links

Medical encyclopedia article on Arachnoid granulation
Wikipedia's article - Arachnoid granulation

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Arachnoid granulation