C. Corbett Wilkinson, Nicholas V. Stence, Cesar A. Serrano, Sarah J. Graber, Lígia Batista-Silverman, Emily Schmidt-Beuchat, and Brooke M. French
Recently, the authors investigated the normal course of fusion of minor lateral calvarial sutures on “3D” volume-rendered head CT reconstructions in pediatric trauma patients. While evaluating these reconstructions, they found many more fused sagittal sutures than expected given the currently accepted prevalence of sagittal craniosynostosis. In the present study, using the same set of head CT reconstructions, they investigated the course of fusion of the sagittal as well as the lambdoid, coronal, and metopic sutures.
They reviewed all volume-rendered head CT reconstructions performed in the period from 2010 through mid-2012 at Children’s Hospital Colorado for trauma patients aged 0–21 years. Each sagittal, lambdoid, coronal, or metopic suture was graded as open, partially fused, or fused. The cephalic index (CI) was calculated for subjects with fused and partially fused sagittal sutures.
After exclusions, 331 scans were reviewed. Twenty-one subjects (6%) had fusion or partial fusion of the sagittal suture. Four of the 21 also had fusion of the medial lambdoid and/or coronal sutures. In the 17 subjects (5%) with sagittal suture fusion and no medial fusion of adjacent sutures, the mean CI was 77.6. None of the 21 subjects had been previously diagnosed with craniosynostosis. Other than in the 21 subjects already mentioned, no other sagittal or lambdoid sutures were fused at all. Nor were other coronal sutures fused medially. Coronal sutures were commonly fused inferiorly early during the 2nd decade of life, and fusion progressed superiorly and medially as subjects became older; none were completely fused by 18 years of age. Fusion of the metopic suture was first seen at 3 months of life; fusion was often not complete until after 2 years.
The sagittal and lambdoid sutures do not usually begin to fuse before 18 years of age. However, more sagittal sutures are fused before age 18 than expected given the currently accepted prevalence of craniosynostosis. This finding is of unknown significance, but likely many of them do not need surgery. The coronal suture often begins to fuse inferiorly early in the 2nd decade of life but does not usually complete fusion before 18 years of age. The metopic suture often starts to fuse by 3 months of age, but it may not completely fuse until after 2 years of age.
C. Corbett Wilkinson, Cesar A. Serrano, Brooke M. French, Sarah J. Graber, Emily Schmidt-Beuchat, Lígia Batista-Silverman, Noah P. Hubbell, and Nicholas V. Stence
Several years ago, the authors treated an infant with sagittal and bilateral parietomastoid suture fusion. This made them curious about the normal course of fusion of “minor” lateral sutures (sphenoparietal, squamosal, parietomastoid). Accordingly, they investigated fusion of these sutures on 3D volume-rendered head CT reconstructions in a series of pediatric trauma patients.
The authors reviewed all volume-rendered head CT reconstructions obtained from 2010 through mid-2012 at Children’s Hospital Colorado in trauma patients aged 0–21 years. Each sphenoparietal, squamosal, and parietomastoid suture was graded as open, partially fused, or fused. In several individuals, one or more lateral sutures were fused atypically. In these patients, the cephalic index (CI) and cranial vault asymmetry index (CVAI) were calculated. In a separately reported study utilizing the same reconstructions, 21 subjects had fusion of the sagittal suture. Minor lateral sutures were assessed, including these 21 individuals, excluding them, and considering them as a separate subgroup.
After exclusions, 331 scans were reviewed. Typically, the earliest length of the minor lateral sutures to begin fusion was the anterior squamosal suture, often by 2 years of age. The next suture to begin fusion—and first to complete it—was the sphenoparietal. The last suture to begin and complete fusion was the parietomastoid. Six subjects (1.8%) had posterior (without anterior) fusion of one or more squamosal sutures. Six subjects (1.8%) had fusion or near-complete fusion of one squamosal and/or parietomastoid suture when the corresponding opposite suture was open or nearly open. The mean CI and CVAI values in these subjects and in age- and sex-matched controls were normal and not significantly different. No individuals had a fused parietomastoid suture with open squamosal and/or sphenoparietal sutures.
Fusion and partial fusion of the sphenoparietal, squamosal, and parietomastoid sutures is common in children and adolescents. It usually does not represent craniosynostosis and does not require cranial surgery. The anterior squamosal suture is often the earliest length of these sutures to fuse. Fusion then spreads anteriorly to the sphenoparietal suture and posteriorly to the parietomastoid. The sphenoparietal suture is generally the earliest minor lateral suture to complete fusion, and the parietomastoid is the last. Atypical patterns of fusion include posterior (without anterior) squamosal suture fusion and asymmetrical squamosal and/or parietomastoid suture fusion. However, these atypical fusion patterns may not lead to atypical head shapes or a need for surgery.