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New insights into the relationship between skull base fusion and torticollis in children
Jisun Hwang1,2, Yoonju Na3, Jin Wook Choi2
11Department of Radiology, Seoul National University Bundang Hospital, Seongnam.
Insights
Unilateral premature fusion of the posterior intraoccipital synchondrosis (UPF-PIOS) is a key cause of pediatric torticollis. This condition presents with a head tilt towards the affected side, indicating a need for early diagnosis.
Area of Science:
- Pediatric Orthopedics
- Craniofacial Surgery
- Radiology
Background:
- Torticollis in children can stem from various causes, including congenital muscular torticollis and bony abnormalities.
- Unilateral premature fusion of the posterior intraoccipital synchondrosis (UPF-PIOS) is a less common but significant etiology.
- Identifying UPF-PIOS is crucial for appropriate diagnosis and management of pediatric head tilt.
Purpose of the Study:
- To investigate the association between UPF-PIOS and head tilt in pediatric patients.
- To describe the clinical characteristics of children with UPF-PIOS and torticollis.
- To highlight UPF-PIOS as an underrecognized cause of torticollis.
Main Methods:
- Retrospective observational study of 1680 children with persistent torticollis undergoing 3D CT.
- UPF-PIOS diagnosis based on skull base asymmetry, CT confirmation, and ≥ 2-mm vertical skull length difference.
- Analysis of clinical features including age, sex, head tilt, and craniovertebral junction abnormalities.
Main Results:
- Fifteen cases of UPF-PIOS were identified (0.89% of evaluated patients).
- Median age at diagnosis was 19 months; most diagnosed before age 3.
- All patients had head tilt towards the UPF-PIOS side, with a median vertical skull length difference of 8.0 mm.
Conclusions:
- UPF-PIOS is an underrecognized cause of pediatric torticollis.
- Characteristic findings include skull base asymmetry and head tilt towards the fused side.
- Recognizing this pattern aids in differential diagnosis and prevents misdiagnosis, such as with lambdoid craniosynostosis.
Objective:
The objective of this study was to investigate the relationship between unilateral premature fusion of the posterior intraoccipital synchondrosis (UPF-PIOS) and head tilt in pediatric patients, as well as to analyze the clinical features of children diagnosed with UPF-PIOS exhibiting torticollis.
Methods:
A retrospective observational study was conducted at the Center for Torticollis in the Department of Physical Medicine and Rehabilitation of a tertiary hospital. Among 14,869 pediatric patients who visited the clinic between January 1, 2005, and July 15, 2024, 1680 children with persistent torticollis underwent 3D CT for further evaluation. UPF-PIOS was diagnosed based on three criteria: 1) asymmetrical posterior skull base on 3D volume-rendered images, 2) confirmation of UPF-PIOS on 3D or axial craniofacial CT, and 3) a ≥ 2-mm vertical skull length difference between the right and left sides on coronal CT images. Clinical characteristics such as sex, age at diagnosis, skull asymmetry, head tilt direction, and craniovertebral junction abnormalities were analyzed.
Results:
Fifteen cases of UPF-PIOS were identified (0.89% of those who underwent imaging). The median age at diagnosis was 19 months, with most diagnosed before age 3 years. The median vertical length difference was 8.0 mm, with the affected side being shorter. All patients exhibited head tilt toward the UPF-PIOS side, and 53% had craniovertebral junction abnormalities.
Conclusions:
UPF-PIOS is an underrecognized cause of torticollis in young children. Its characteristic clinical features include an asymmetrical posterior skull base, shortening of the skull on the affected side, and a head tilt toward the side of the prematurely fused synchondrosis. Recognizing this pattern-a tetrad of unilateral synchondrosis fusion and the three resultant findings-is clinically important for differential diagnosis. Considering UPF-PIOS in children with torticollis (especially when physical therapy fails) can prevent misdiagnosis (e.g., distinguishing it from lambdoid craniosynostosis) and guide appropriate management. Further research with larger cohorts and long-term follow-up is warranted to confirm these findings.
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