A refined radiological classification of anterior clinoid process pneumatization

Area of Science:

• Neurosurgery
• Radiology
• Anatomy

Background:

• Anterior clinoid process (ACP) pneumatization presents risks in skull base surgery, including CSF leakage and optic nerve injury.
• Existing classifications do not fully capture clinically significant variations involving the optic strut or planum sphenoidale.

Purpose of the Study:

• To determine the prevalence and morphological patterns of ACP pneumatization in a Thai population.
• To propose a refined radiological classification system for ACP pneumatization based on its route and extent.

Main Methods:

• Retrospective CT-based study of 400 ACPs from 200 patients (aged ≥10 years).
• Categorization of pneumatization patterns into eight subtypes based on route (optic strut, planum sphenoidale, or both) and degree of ACP involvement (≤50% or >50%).
• Assessment of ACP morphometric data and associated bone variations.

Main Results:

• ACP pneumatization observed in 30.8% of cases, with bilateral involvement in 5%.
• Most frequent subtype: isolated optic strut pneumatization (16%).
• Males showed significantly greater ACP base width and length compared to females.

Conclusions:

• ACP pneumatization, particularly via the optic strut, is a common anatomical variation.
• The proposed eight-subtype classification offers a detailed framework for preoperative imaging and communication.
• Findings are relevant to both transcranial and endoscopic endonasal approaches, especially for optic canal exposure.