What segment of the Internal Carotid Artery (ICA) does the blood supply of the pituitary gland derive from?

Blood Supply of the Pituitary Gland

The blood supply of the pituitary gland is primarily derived from the cavernous segment of the internal carotid artery (ICA).

Arterial Supply to the Pituitary Gland

Superior Hypophyseal Arteries (SHAs)

• Originate from the medial aspect of the cavernous segment of the ICA 1, 2
• Supply the anterior pituitary gland (adenohypophysis) and pituitary stalk
• Characteristics:
  • Number: 1-3 per side (average 1.7 per side) 2
  • Typically arise from the proximal half of the segment between the origins of the ophthalmic and posterior communicating arteries 3
  • Approximately 44% originate from the "carotid cave" region 1
  • Average diameter: 0.25 mm 3

Inferior Hypophyseal Arteries (IHAs)

• Originate predominantly from the meningohypophyseal trunk (92.5% of cases) 4
• In some cases (7.5%), arise directly from the cavernous segment of the ICA 4
• Supply primarily the posterior pituitary (neurohypophysis)
• Enter the posterior third of the medial wall of the cavernous sinus in 75% of cases 4

Additional Arterial Supply

• Infundibular arteries: Originate from the posterior communicating artery 5, 3
• Prechiasmal arteries: Originate from the ophthalmic artery (less common) 5, 3
• Capsular arteries: Originate from the cavernous segment of the ICA 5

Vascular Networks

• "Circuminfundibular anastomosis": Rich vascular network around the pituitary stalk 5
• "Inferior hypophyseal arterial circle" (or inferior capsular arterial rete): Network at the base of the pituitary 5

Clinical Significance

• Understanding the vascular anatomy is critical for surgical approaches to the sellar and parasellar regions
• SHAs are in close proximity to the optic apparatus and can supply the optic nerves (86%), chiasm (57%), and infundibulum (86%) 2
• The relationship between SHAs and superior hypophyseal aneurysms is consistent 1
• IHAs typically run in close relation to the lower third of the posterior clinoid process (80% of cases) 4

Imaging Considerations

• SHAs can now be visualized with high-resolution cone beam CT angiography (CBCTA) 1
• Conventional angiography remains the gold standard for detailed visualization of these small vessels

The vascular supply of the pituitary gland forms an intricate network that ensures adequate perfusion of this critical endocrine organ, with the cavernous segment of the ICA serving as the primary source of blood supply through its branches.