The paraclinoid aneurysms and the distal dural ring: a new classification

Area of Science:

• Neurosurgery
• Neuroanatomy
• Radiology

Background:

• Paraclinoid aneurysms present classification challenges due to complex anatomy and lack of reference points.
• Existing terminology and classification systems for these aneurysms are often contradictory.

Purpose of the Study:

• To conduct a surgical anatomical study of the paraclinoid region to identify a key anatomical reference.
• To propose a novel classification system for paraclinoid aneurysms centered on the distal dural ring (DDR).
• To develop radiological guidelines for differentiating intra- and extradural lesions.

Main Methods:

• Surgical anatomical dissection of 10 human cadaveric heads focusing on the DDR, anterior clinoid process (ACP), and internal carotid artery segments.
• Radiological evaluation of 50 skulls and 5 injected cadaveric heads to establish criteria for DDR identification.
• Development of a new aneurysm classification based on anatomical findings related to the DDR.

Main Results:

• The distal dural ring (DDR) is identified as the key anatomical landmark.
• A new classification categorizes paraclinoid aneurysms into four groups: supra-DDR, para-DDR, infra-DDR, and transitional.
• Radiological identification of specific landmarks (planum sphenoidale, tuberculum sellae, optic canal) aids in distinguishing intra- from extradural lesions.

Conclusions:

• A new classification for paraclinoid aneurysms utilizing the DDR as the central anatomical element is proposed.
• Radiological guidelines are established to identify the DDR, facilitating the distinction between intra- and extradural aneurysms.