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Pituitary stalk

The pituitary stalk, also known as the infundibulum, is a slender, funnel-shaped structure connecting the hypothalamus to the pituitary gland. It plays a vital role in neuroendocrine integration, facilitating the transport of hormones and regulatory signals between the brain and the pituitary. Positioned within the suprasellar cistern, it is surrounded by cerebrospinal fluid and bordered superiorly by the optic chiasm. The pituitary stalk is a key structure in both anatomical and functional imaging due to its involvement in various pathological processes including tumors, inflammatory conditions, and traumatic injuries.

Synonyms

  • Infundibulum

  • Hypophyseal stalk

  • Pituitary infundibulum

Function

  • Connects the hypothalamus to the pituitary gland.

  • Transmits releasing and inhibitory hormones from the hypothalamus to the anterior pituitary.

  • Carries axons from hypothalamic nuclei (especially supraoptic and paraventricular nuclei) to the posterior pituitary, mediating release of ADH and oxytocin.

  • Essential for hypothalamic-pituitary axis regulation.

Arterial Supply

  • Superior hypophyseal arteries: Branches of the internal carotid artery, primarily supply the pituitary stalk and anterior pituitary.

  • Inferior hypophyseal arteries: Also arise from the internal carotid artery, primarily supply the posterior pituitary but may contribute to the stalk.

  • Circle of Willis: Minor contributions via perforating branches.

Venous Drainage

  • Hypophyseal portal veins: Drain the anterior pituitary and pituitary stalk into the cavernous sinus.

  • Cavernous sinus: Major venous outflow structure, draining into the superior and inferior petrosal sinuses.

  • Inferior hypophyseal veins: Drain the posterior pituitary and part of the stalk.

MRI Appearance

  • T1-weighted:

    • Stalk appears as a thin, isointense to slightly hyperintense structure compared to brain parenchyma.

    • Posterior pituitary “bright spot” may be seen at the distal stalk (if visualized).

  • T2-weighted:

    • Stalk is isointense or mildly hypointense relative to gray matter.

    • Cerebrospinal fluid (CSF) around the stalk appears hyperintense, highlighting the structure.

  • FLAIR:

    • Stalk remains isointense; surrounding CSF is suppressed, further delineating the stalk’s margins.

  • Post-Contrast T1 (Gadolinium-enhanced):

    • Stalk enhances uniformly and intensely.

    • Any thickening or irregular enhancement may indicate pathology (e.g., inflammation, tumor).

CT Appearance

  • Non-contrast CT:

    • The pituitary stalk is generally not well-visualized due to its small size and similar density to surrounding brain structures.

    • May appear as a thin, isodense line above the pituitary gland in high-resolution studies.

  • Contrast-Enhanced CT:

    • Mild to moderate enhancement of the stalk can sometimes be appreciated, though less conspicuous than MRI.

MRI images

Pituitary stalk mri 3t coronal image

MRI images

Pituitary stalk mri 3t sagittall image

CT image

Pituitary stalk CT image