What is the origin of the anterior choroidal artery?

Origin of the Anterior Choroidal Artery

The anterior choroidal artery (AChA) originates from the internal carotid artery (ICA), typically arising from its posteroinferior aspect distal to the posterior communicating artery and proximal to the internal carotid bifurcation. 1, 2

Anatomical Details

The anterior choroidal artery has the following characteristics:

• Origin point: Arises from the internal carotid artery
• Specific location on ICA: Most commonly (60%) from the posteroinferior aspect of the ICA 1
• Less common origins: Posterolateral aspect (22.2%) or anterior part (2%) of the ICA 1
• Positional relationships:
  • Located approximately 5.3 mm distal to the posterior communicating artery 1
  • Located approximately 4.0 mm proximal to the bifurcation of the carotid artery 1
  • Average diameter: 0.94 mm (range 0.7-1.2 mm) 1

Course and Segments

The cisternal segment of the AChA can be divided into two parts:

1. Preoptic part:

   • Extends from its origin at the ICA to the artery's genu (the most medial extension point)
   • Perforating branches arise from the superolateral portion and course laterally 3

2. Postoptic part:

   • Extends from the genu to the inferior choroidal point
   • Typically longer than the preoptic part
   • Contains more perforating arteries (4.6 vs 3.4 per hemisphere) 3
   • Perforators arise from the inferomedial portion and course medially 3

Anatomical Variations

While the typical origin is from the ICA, rare anatomical variants have been documented:

• The AChA may occasionally arise proximal to an ipsilateral fetal posterior cerebral artery 4
• The genu of the AChA is typically located 8 mm medial to the artery's origin 3
• In 13% of cases, the genu is located medial to the optic tract 3

Clinical Significance

The AChA supplies critical structures including:

• Internal capsule
• Optic tract
• Lateral geniculate body
• Thalamus
• Cerebral peduncle
• Choroid plexus 2, 3

Understanding the precise origin and course of the AChA is crucial for neurosurgical procedures in the region of the internal carotid artery and perimesencephalic cisterns, as damage to this vessel can result in significant neurological deficits due to its supply to critical motor and sensory structures.