Basal Perforating Arteries of the Anterior Communicating Artery: Anatomical Study and Implications for Suprachiasmatic Region Surgery

Background Lesions occupying the suprachiasmatic subcallosal space, including aneurysms and tumors, may have an intimate relationship with the anterior communicating artery (AComA). Injury to the AComA’s branches, specifically to the subcallosal artery (SbA), could result in severe cognitive and memory dysfunction due to infarction of the associated basal forebrain. Here, we aim to evaluate the anatomical variations of the basal perforating branches of the AcomA, with emphasis on the SbA, and we discuss the clinical implications of the findings when approaching the suprachiasmatic subcallosal region from endoscopic endonasal and transcranial routes.

Methods The origin, course, diameter, and branching pattern of the basal perforating branches of the AcomA (subcallosal, hypothalamic, and chiasmatic) were studied in 33 specimens, from both transcranial (pterional and interhemispheric approaches) and endonasal perspectives.

Results The SbA was present in 79% of the specimens as a single dominant artery arising from the posterior or posterosuperior surface of the AcomA. It arose from the AcomA, either along with the hypothalamic arteries in 55% or as a single artery in 24%; its mean diameter was 0.5 ±  0.13 mm. Its course was first posteriorly toward the region of the lamina terminalis, where it then curved superiorly to reach the subcallosal area. The SbA gave off many terminal branches to provide the main blood supply to the subcallosal region. Importantly, it supplied blood bilaterally to the septal/subcallosal region in all cases. Therefore, disruption of the SbA could lead to bilateral vascular compromise of the septal area and result in a devastating neurological deficit. In the remaining 21% specimens with no SbA, the median callosal artery (MdCA) was present as the dominant artery arising from the AcomA, either along with the hypothalamic arteries in 15% or as a single artery in 6%; its mean diameter was 1.11 ±  0.58 mm. The SbA and the MdCA never occurred together. The MdCA followed an identical course as that of the SbA and provided supply to the same structures bilaterally, but its distal extension reached the body and even splenium of the corpus callosum. Therefore, the MdCA can be considered a variant of the SbA with a longer trajectory. The hypothalamic arteries were found in all cases, with a mean diameter of 0.2 ±  0.07 mm. They arose from the AcomA (56%), from the A1–AcomA junction (34%), and from the A1 segment (10%). These arteries supplied the anterior hypothalamus and frequently anastomosed with branches of the SbA. The chiasmatic arteries were present in 85% of cases. They arose from the A1 in 39% of cases, from the A1–AcomA junction in 36%, and from the AcomA in 25%. These arteries supplied the upper surface of the optic chiasm and optic tract.

Conclusion The SbA is a unique vessel because it supplies the subcallosal region bilaterally. The anterior hypothalamic region is supplied by multiple branches from the AcomA and also from the A1. Preservation of these vessels during surgery to treat suprachiasmatic tumors or aneurysms with posteroinferior projection is crucial to a successful outcome.

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