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Posterior median sulcus of medulla oblongata

The posterior median sulcus of the medulla oblongata is a shallow midline longitudinal groove on the dorsal surface of the medulla. It represents the external surface landmark corresponding to the internal midline septation between paired posterior column pathways and serves as an important anatomical reference on the dorsal brainstem.

This sulcus is clinically relevant in neuroanatomy, neuroimaging orientation, and dorsal brainstem pathology, particularly in lesions affecting the posterior columns and fourth ventricle region.

Synonyms

  • Dorsal median sulcus of the medulla

  • Posterior midline sulcus (medullary)

Location

  • Situated along the midline of the dorsal surface of the medulla oblongata

  • Extends inferiorly from the caudal end of the fourth ventricle

  • Continuous inferiorly with the posterior median sulcus of the spinal cord

  • Separates the paired gracile fasciculi on either side

  • Lies posterior to the central canal region in the closed (caudal) medulla

  • Located inferior to the obex in the open (rostral) medulla

Anatomical components

  • Surface landmark:

    • Shallow longitudinal groove without contained neural tissue

  • Underlying structures:

    • Posterior median septum

    • Medial portions of the dorsal columns

  • Functional association:

    • Closely related to the gracile tracts and nuclei (inferiorly)

Relations

Anteriorly:

  • Central gray matter and central canal (closed medulla)

  • Fourth ventricle (open medulla, indirectly)

Posteriorly:

  • Dorsal surface of the medulla oblongata

Laterally:

  • Posterior intermediate sulcus (when present)

  • Gracile fasciculus (medially)

  • Cuneate fasciculus (more laterally, at upper levels)

Superiorly:

  • Obex and caudal fourth ventricle

Inferiorly:

  • Posterior median sulcus of the spinal cord

Associated neural structures

  • Gracile fasciculus (bilateral)

  • Gracile nuclei (deep to rostral portion)

  • Posterior columns conveying proprioception, vibration, and fine touch from the lower body

Function

  • Anatomical separation: Marks the midline division of posterior column pathways

  • Neuroanatomical orientation: Key dorsal landmark for identifying medullary levels

  • Functional correlation: Indirectly related to somatosensory pathways of the lower limbs

MRI appearance

T1-weighted images:

  • Normal: Thin midline indentation on the dorsal medullary surface

  • Signal: Adjacent medullary parenchyma shows homogeneous intermediate signal

T2-weighted images:

  • Normal: Subtle midline cleft with surrounding low-to-intermediate medullary signal

FLAIR:

  • Normal: Typically inconspicuous sulcus

Post-contrast T1-weighted images:

  • Normal: No enhancement related to the sulcus

CT appearance

Non-contrast CT:

  • Normal: Usually not visualized due to limited posterior fossa resolution

MRI images

MRI Posterior median sulcus of medulla oblongata axial anatomy image -img-00000-00000

MRI images

MRI Posterior median sulcus of medulla oblongata coronal anatomy image -img-00000-00000