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Radiographic Clarity of the External Auditory Meatus as a Cranial Reference Point in Spinal Deformity Patients: A
Dongkyu Kim1, Dong Kyu Chin1, Sejun Park1
1Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea.
Journal of Clinical Medicine
|May 4, 2026
Summary
The external auditory meatus (EAM) is less reliable than the sella turcica as a cranial reference point due to poor radiographic clarity and lower interobserver reproducibility. This suggests limitations for EAM use in neurosurgical applications.
Area of Science:
- Neurosurgery
- Radiology
- Orthopedics
Background:
- The external auditory meatus (EAM) is often used as a cranial reference point near the midpoint of the nasion-inion line (MNI).
- Radiographic clarity and reliability of the EAM as a landmark have not been extensively validated.
- The sella turcica serves as a control landmark for comparison.
Purpose of the Study:
- To evaluate the radiographic clarity of the EAM.
- To assess the interobserver reproducibility of the EAM compared to the sella turcica.
- To determine the suitability of the EAM as a cranial reference landmark.
Main Methods:
- Retrospective review of preoperative standing whole-spine radiographs from patients undergoing sagittal spinal deformity correction.
- Measurement of horizontal and vertical distances from EAM and sella turcica to MNI.
- Assessment of radiographic clarity and interobserver reliability using intraclass correlation coefficient (ICC).
Main Results:
- The EAM was horizontally closer to MNI (1.1 mm) but had significantly poorer radiographic clarity (14.1% clear vs. 84.5% for sella turcica).
- Interobserver reproducibility was lower for EAM (ICC 0.84-0.89) than for sella turcica (ICC 0.95-0.97).
- Greater horizontal deviation was observed for EAM measurements among observers (6.3 mm vs. 2.2 mm).
Conclusions:
- The external auditory meatus exhibits inferior radiographic clarity and reproducibility compared to the sella turcica.
- The EAM's anatomical proximity to the midpoint of the nasion-inion line does not guarantee its reliability as a cranial reference landmark.
- Findings indicate potential limitations of using the EAM in neurosurgical and orthopedic contexts requiring precise landmark identification.
