Positional relationship between the external acoustic meatus and sigmoid sinus: an MRI study

Area of Science:

• Anatomy
• Radiology
• Neurosurgery

Background:

• Detailed anatomical studies of the external acoustic meatus (EAM) and sigmoid sinus (SS) are lacking.
• Understanding their positional relationship is crucial for surgical interventions.

Purpose of the Study:

• To characterize the positional relationship between the EAM and SS.
• To utilize contrast magnetic resonance imaging (MRI) for detailed analysis.

Main Methods:

• Conducted thin-sliced, contrast MRI on 85 patients with intact EAM and SS.
• Analyzed imaging data to assess relationships, distances, and cross-sectional shapes.

Main Results:

• EAM and SS were clearly visualized in all patients.
• Significant variability and left-right asymmetry were observed in their relationships and distances.
• The 'intervening' type of positional relationship was most common (85%).
• Shortest distance between EAM posterior wall and SS anterior margin averaged 12.3 mm (right) and 13.0 mm (left).
• A distance <5 mm was noted in three female patients on the right side.

Conclusions:

• The positional relationship between EAM and SS is highly variable and inconsistent.
• These structures can be closely adjacent, particularly on the right side.
• Presurgical contrast MRI is essential for planning surgeries in the EAM region.