Posterior median sulcus

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Structure of the white matter of the spinal cord in cross section.

The posterior median sulcus, also known as the dorsal median sulcus, is a shallow groove found in the midline of the posterior aspect of the spinal cord, medulla oblongata and pons. In the spinal cord, it is the external boundary of the posterior median septum and separates the two posterior funiculi. 

The posterior median sulcus of the spinal cord is continuous superiorly in the closed part of the medulla oblongata, being gradually shallower proximally. Here, it separates the two gracile fasciculi which ascend from the spinal cord. The pons also bears a median sulcus in the midline of it's posterior surface, which is continuous with that of the medulla oblongata and the spinal cord. 

The posterior (median) medullary vein may run along the posterior median sulcus of the medulla oblongata, which then becomes continuous with the posterior (median) spinal vein in the posterior median sulcus in the spinal cord.