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The petromastoid canal in the young child: appearance on computed tomography
Christoph Kenis1, Michael Ditchfield, Eldho Paul
1Department of Radiology, Antwerp University Hospital & University of Antwerp, Wilrijkstraat 10, 2650 Edegem, Antwerp, Belgium. christophkenis@hotmail.com
Insights
The petromastoid canal (PMC) is wide in children under two years old, narrowing as they grow. This change correlates with temporal bone pneumatization and otic capsule ossification.
Area of Science:
- Anatomy
- Pediatric Radiology
- Temporal Bone Imaging
Background:
- The petromastoid canal (PMC) is typically narrow in adults.
- In young children, the PMC can appear wide on high-resolution CT (HRCT) scans.
Purpose of the Study:
- To evaluate the age-related changes in width and shape of the petromastoid canal (PMC) in young children.
- To document the progression of PMC morphology from infancy through early childhood.
Main Methods:
- Retrospective review of temporal bone HRCT scans from 80 children (0.3-6.9 years).
- Analysis of PMC width and categorization into subtypes.
- Correlation of PMC dimensions with age, pericapsular ossification, and mastoid pneumatization.
Main Results:
- Average PMC width was 1.95 mm in children < 2 years, significantly wider than 0.83 mm in children ≥ 2 years (p < 0.001).
- Bulky (type III) PMC was predominant in younger children (< 2 years), while thin curvilinear (type I) PMC was more common in older children.
- PMC width showed inverse correlation with pericapsular ossification and mastoid pneumatization (p < 0.001).
Conclusions:
- A wide petromastoid canal (≥ 1 mm) is a common finding in children under two years old.
- The PMC progressively narrows with age, associated with increased temporal bone pneumatization and otic capsule ossification.
Objective:
The adult petromastoid canal (PMC) is a thin anatomical structure, but in young children, it can be wide on high resolution CT (HRCT) scans. We performed this study to evaluate the year-by-year change in width and shape of the PMC in the young child.
Materials And Methods:
We retrospectively reviewed temporal bone HRCT scans, performed between 2007 and 2012. Eighty children were included (age range: 0.3-6.9 years; median age: 3.1 years; 56% male). All scans had a slice thickness of ≤ 1 mm.
Results:
The average width of the PMC was 1.95 mm in children < 2 years, compared to 0.83 mm in children ≥ 2 (p < 0.001). We categorized the PMC into 4 subtypes. A bulky (type III) PMC was predominant < 2 years. A thin curvilinear (type I) PMC was more prevalent in the older children. Type II and IV PMC were found infrequently. The PMC width correlated inversely with the degree of pericapsular ossification (p<0.001), and mastoid pneumatisation (p < 0.001).
Conclusion:
A wide PMC (≥ 1 mm) is a common finding in children < 2 years. As children grow older, the PMC progressively narrows. This correlates to increased temporal bone pneumatisation and ossification of the otic capsule.
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