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Hypothalamic sulcus

The hypothalamic sulcus is a shallow longitudinal groove located on the lateral wall of the third ventricle. It serves as an important anatomical landmark that demarcates the thalamus superiorly from the hypothalamus inferiorly. Although it is not a functional pathway itself, it is crucial for anatomical orientation within the diencephalon.

The hypothalamic sulcus is widely used in neuroanatomy and neuroimaging as a reference line for defining hypothalamic and thalamic boundaries.

Synonyms

  • Sulcus hypothalamicus

Location

  • Situated on the lateral wall of the third ventricle

  • Extends from the interventricular foramen (foramen of Monro) anteriorly

  • Runs posteriorly toward the cerebral aqueduct

  • Forms the boundary between:

    • Thalamus (superior)

    • Hypothalamus (inferior)

  • Present bilaterally, one on each side of the third ventricle

Anatomical description

  • Appears as a shallow linear groove

  • Not a true sulcus of the brain surface, but an intraventricular landmark

  • Separates epithalamic and thalamic structures from hypothalamic structures

  • Does not contain neural tracts or nuclei

Relations

Superiorly:

  • Thalamus

  • Interthalamic adhesion (when present)

Inferiorly:

  • Hypothalamus

  • Tuber cinereum and mammillary body region (posteriorly)

Medially:

  • Third ventricle cavity

Laterally:

  • Thalamic and hypothalamic gray matter

Anteriorly:

  • Foramen of Monro

Posteriorly:

  • Region of the cerebral aqueduct

Associated structures

  • Thalamus: Sensory relay and integration center

  • Hypothalamus: Autonomic, endocrine, and homeostatic regulation

  • Third ventricle: CSF-filled midline cavity of the diencephalon

Function

  • Anatomical demarcation: Clearly separates thalamic and hypothalamic regions

  • Orientation landmark: Assists in localization of diencephalic structures

  • Imaging reference: Used to identify normal anatomy on MRI and CT

MRI appearance (normal)

T1-weighted images:

  • Hypothalamic sulcus: Appears as a thin linear indentation along the lateral wall of the third ventricle

  • Signal: Follows adjacent gray matter signal

  • Best appreciated on axial images through the third ventricle

T2-weighted images:

  • Normal: Subtle linear groove separating thalamus and hypothalamus

  • CSF in third ventricle: High signal accentuates the sulcus margin

FLAIR:

  • Normal: CSF suppression highlights the ventricular wall

  • Sulcus: Seen indirectly as a contour between thalamus and hypothalamus

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal: No enhancement

CT appearance (normal)

Non-contrast CT:

  • Hypothalamic sulcus: Not directly visualized

  • Identified indirectly by third ventricle contour and adjacent gray matter

Post-contrast CT:

  • Normal: No enhancement

MRI image

MRI Hypothalamic sulcus anatomy image -img-00000-00000

MRI image

MRI Hypothalamic sulcus anatomy image -img-00000-00000_00001