Pituitary Entry Zone: Newly Midline Hypovascular Area in Pituitary Gland

Clinical observations suggest relative preservation of endocrine function following midline incisions during transsphenoidal pituitary surgery, despite the gland's rich vascularity. This study aimed to investigate the intrapituitary microvascular architecture to identify a potential anatomical correlate for this functional resilience.

This descriptive observational study utilized 3 human cadaveric pituitary glands. Histologic sections were prepared in sagittal and coronal planes. Immunohistochemistry for the endothelial marker CD34 was performed to assess microvascular density (MVD). MVD was quantified and compared between the central midline region and the peripheral zone in both sagittal and coronal sections.

In the sagittal plane, MVD was significantly reduced in the midline region (mean: 7,642 vessels/mm²) compared to the peripheral region (mean: 31,330 vessels/mm²). Conversely, no significant difference in MVD was observed between the central (mean: 32,090 vessels/mm²) and peripheral (mean: 28,270 vessels/mm²) regions in the coronal plane.

This study identifies a distinct zone of relative hypovascularity along the sagittal midline of the human pituitary gland, which we propose naming the pituitary entry zone. This anatomical finding offers a potential histologic basis for the observed preservation of pituitary function after midline surgical approaches. While limited by a small sample size, these results highlight a previously under-characterized aspect of pituitary angioarchitecture that may represent a safer corridor for surgical intervention. Further investigation correlating this anatomical finding with postoperative outcomes is warranted.