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Sylvian cistern

The Sylvian cistern, also known as the lateral cerebral fissure cistern, is a subarachnoid space surrounding the lateral sulcus (Sylvian fissure) that contains cerebrospinal fluid (CSF), the middle cerebral artery (MCA) and its branches, and proximal cranial nerves. It is formed by the splitting of the arachnoid membrane over the lateral fissure, creating a CSF-filled compartment that allows vascular and neural structures to traverse safely.

The Sylvian cistern is divided into proximal (insular) and distal (opercular) portions, with the proximal portion lying over the insula and the distal portion extending toward the cortical opercula. It communicates with other subarachnoid cisterns, including the basal cisterns and interhemispheric fissure cisterns, facilitating CSF flow. The cistern’s configuration is clinically important for aneurysm evaluation, subarachnoid hemorrhage assessment, and surgical planning.

Function

  • Houses cerebrospinal fluid (CSF) for cushioning and protection of brain structures

  • Provides a vascular corridor for the middle cerebral artery and branches

  • Offers a protective space for cranial nerves passing through the lateral fissure

  • Acts as a surgical corridor during approaches to insular or opercular regions

  • Facilitates CSF circulation between basal and cortical cisterns

Synonyms

  • Lateral cerebral fissure cistern

  • Lateral sulcus cistern

  • Cistern of Sylvius

MRI Appearance

T1-weighted images:

  • The Sylvian cistern appears as a well-defined low signal intensity (hypointense) CSF-filled space

  • Surrounding brain parenchyma is intermediate signal intensity, providing clear contrast

  • Vascular structures within the cistern (e.g., MCA) may appear as flow voids

T2-weighted images:

  • CSF within the Sylvian cistern is hyperintense, clearly delineating the cistern margins

  • Brain parenchyma is intermediate signal intensity, enhancing visualization of the cistern

  • Useful for detecting arachnoid cysts, subarachnoid hemorrhage, or vascular anomalies

STIR (Short Tau Inversion Recovery):

  • CSF remains hyperintense

  • Surrounding edema or inflammatory changes in adjacent brain tissue appear hyperintense

  • Sensitive for cortical or subarachnoid pathology

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal Sylvian cistern shows no enhancement, as CSF is not vascularized

  • Pathological processes (e.g., infection, tumor, or leptomeningeal disease) may cause enhancement along cisternal surfaces or vascular structures

CT Appearance:

  • Sylvian cistern is visualized as a low-density CSF-filled space lateral to the insular cortex

  • Brain parenchyma is higher density, creating clear contrast

  • Hyperdense lesions, hemorrhage, or cystic masses are readily identified

  • CT is especially useful for acute subarachnoid hemorrhage, hydrocephalus, and mass effect assessment

MRI images

Sylvian cistern mri axial iamge