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Chiasmatic cistern

The Chiasmatic cistern is an important subarachnoid space situated at the base of the brain, closely related to the optic chiasm and surrounding neurovascular structures. It serves as a key CSF (cerebrospinal fluid) reservoir and an anatomical landmark in neuroimaging and neurosurgery. The cistern houses crucial vessels and nerves, making its assessment critical in conditions affecting the sellar and suprasellar regions.

Synonyms:

  • Suprasellar cistern

  • Prechiasmatic cistern

  • Cistern of the optic chiasm

Function:

  • Acts as a CSF-filled space buffering the optic chiasm, pituitary stalk, and adjacent hypothalamic structures.

  • Provides a conduit for passage of neurovascular structures, notably:

    • Optic nerves and optic chiasm

    • Pituitary stalk (infundibulum)

    • Superior hypophyseal arteries

  • Serves as an anatomical landmark for the assessment of sellar and suprasellar pathologies (e.g., pituitary macroadenoma, craniopharyngioma, aneurysms).

  • Plays a role in the spread of infections, hemorrhages, or tumors involving the suprasellar region.

MRI Appearance:

  • T1-weighted imaging:

    • The chiasmatic cistern appears hypointense (dark) due to its CSF content.

    • Surrounding neural structures (optic chiasm, pituitary stalk) are isointense to brain parenchyma.

    • Pathologies (e.g., masses or hemorrhage) may alter its normal signal or contour.

  • T2-weighted imaging:

    • The cistern appears hyperintense (bright) as CSF is bright on T2.

    • Clearly demarcates the optic chiasm and infundibulum against the bright CSF background.

    • Lesions, blood products, or mass effect may be evident as areas of altered signal.

  • FLAIR (Fluid-Attenuated Inversion Recovery):

    • The cistern appears hypointense (dark) since FLAIR suppresses free fluid signal (CSF).

    • Any abnormal signal within the cistern (e.g., blood, proteinaceous fluid, pus) appears hyperintense (bright), aiding detection of pathology (e.g., subarachnoid hemorrhage, infection).

CT Appearance:

  • The chiasmatic cistern is seen as a hypodense (dark) space anterior and superior to the sella turcica, outlining the optic chiasm and adjacent structures.

  • It may be effaced or distorted by mass lesions (e.g., pituitary macroadenoma, suprasellar tumors, aneurysms).

  • Acute blood (e.g., subarachnoid hemorrhage) appears hyperdense (bright) within the cistern.

  • Calcifications (e.g., craniopharyngioma) or enhancing lesions may be seen in or around the cistern.

MRI images

Chiasmatic cistern mri 3t axial image

MRI images

Chiasmatic cistern mri 3t coronal image

MRI images

Chiasmatic cistern mri 3t sagittal image

CT image

Chiasmatic cistern CT axial anatomy image -img-00001-00001