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Observations on the growth of temporalis muscle: A 3D CT imaging study
Giulia Moltoni1, Felice D'Arco2, Maria Camilla Rossi-Espagnet1,3
1Neuroradiology Unit, Department of Neuroscienze, Salute Mentale e Organi di Senso (NESMOS), Sapienza University, Rome, Italy.
Insights
During childhood, temporalis muscle growth, especially vertical, outpaces skull development, potentially explaining deformities after early craniofacial surgery.
Area of Science:
- Craniofacial anatomy
- Pediatric growth and development
- Skeletal biology
Background:
- Childhood temporalis muscle development is crucial for mastication.
- Understanding its growth relative to the skull is key to identifying craniofacial anomalies.
- Previous research has not fully elucidated the age-related expansion of temporalis origins versus skull growth.
Purpose of the Study:
- To test the hypothesis of disproportionate age-related expansion of temporalis muscle origin compared to skull growth in children.
- To investigate the relationship between temporalis muscle growth, skull development, and the anterior temporal crest.
- To explore potential links between altered temporalis muscle growth and craniofacial deformities.
Main Methods:
- Analysis of 50 pediatric 3D CT scans (ages 0.6-15 years).
- Measurement of temporalis muscle and skull dimensions in vertical and horizontal planes.
- Assessment of anterior temporal crest development and correlation with age.
Main Results:
- Temporalis muscle showed a statistically significant increase in vertical reach with age (R=0.7826, p<0.05) compared to skull growth.
- Horizontal reach also increased significantly (R=0.5073, p<0.001), but to a lesser extent.
- A fully formed temporal crest was observed at a significantly later mean age (10.6 years) than in other subjects (6.0 years).
Conclusions:
- Childhood temporalis muscle exhibits disproportionate vertical and horizontal growth over its bony origins relative to skull expansion.
- This growth is likely driven by increased masticatory/dietary demands.
- Surgical intervention during early childhood may disrupt this natural growth process, contributing to late-developing craniofacial deformities.
Abstract:
This study investigates the hypothesis that there is, during childhood, a disproportionate age-related expansion of the origin of temporalis muscle compared to the growth of the underlying skull. Lateral projections of 50 randomly selected 3D reformatted computerized tomographic (CT) scans (yielding 100 temporalis muscles) of children aged >0.6 to 15 years scanned for conditions that did not affect the shape of their head or face were windowed to provide the optimum delineation of temporalis muscle against the underlying bone. Vertical and anterior-posterior measurements of the muscle made independently by two observers were compared with those of the skull along the same planes. The development of the anterior temporal crest was also assessed. The intraclass correlation coefficient for differences in the measurements made by each observer ranged from good to excellent. The muscle and skull measurements were used to produce a ratio of muscle-to-skull lengths in both vertical and horizontal planes. Analysis of these ratios showed a statistically significant increase in the vertical reach of temporalis with age (Pearson correlation coefficient (R) =0.7826; p < 0.05) compared to the growth of the skull along the planes chosen for the study-but less so for its horizontal reach (R = 0.5073. p < .001). There were no significant differences between right/left or male/female measurements. There was also a substantial level of agreement between both observers in their assessment of the development of the temporal crest. The mean age of children in whom a fully formed temporal crest could be identified (10.6 years) was significantly greater (p < 0.001) than that of the 38 remaining subjects (6.0 years). These results confirm that there is, in response to increased masticatory/dietary demands during childhood, a disproportionate increase in the vertical and (to a lesser extent) horizontal reach of temporalis muscle over its origin from the temporal, frontal, sphenoid, and parietal bones compared the growth of the skull. It is proposed that surgical interference with this normal process is responsible for the soft tissue component of late-developing deformity that can occur following early (at 6-18 months of age) operations for the correction of trigonocephalic head shape associated with metopic synostosis.
