Arachnoid granulation

Arachnoid granulations (also known as Pacchionian granulations) are small protrusions of the arachnoid mater (the middle layer of the meninges) into the outer membrane of the dura mater. They protrude into the venous sinuses of the brain, and allow cerebrospinal fluid (CSF) to exit the subarachnoid space and enter the blood stream.

Structure

Arachnoid granulations are composed of clusters of arachnoid cells. They are located in the dura mater, the outermost of the three layers of the meninges. The granulations are most commonly found in the superior sagittal sinus, one of the venous sinuses of the brain, but can also be found in other dural sinuses.

Function

The primary function of arachnoid granulations is the reabsorption of cerebrospinal fluid (CSF) from the subarachnoid space into the venous system. This is a crucial process in the circulation of CSF, maintaining a balance between the amount of CSF produced and the amount absorbed.

Clinical significance

Arachnoid granulations can become enlarged or hypertrophic in certain conditions, such as idiopathic intracranial hypertension. This can lead to the formation of arachnoid cysts, which can cause symptoms such as headaches, seizures, and visual disturbances.

See also

• Arachnoid mater
• Cerebrospinal fluid
• Dura mater
• Meninges
• Venous sinuses

References

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Arachnoid_granulation

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  Diagram of the brain showing arachnoid granulations
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  Close-up of arachnoid granulations
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  Illustration of the brain with arachnoid granulations
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  Anatomical drawing of arachnoid granulations
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  CT scan of a pacchionian body in the transverse plane
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  CT image showing Pacchioni granulation