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Characteristics of the infant Apert skull and its subsequent development
1Department of Pediatric Dentistry, Royal Dental College, Copenhagen, Denmark.
Insights
Infant Apert syndrome skulls show premature coronal suture closure and a midline calvarial defect in early infancy. This defect closes by age 4, but normal sutures do not form, indicating early fetal growth inhibition.
Area of Science:
- Craniofacial development
- Pediatric radiology
- Medical genetics
Background:
- Apert syndrome is a genetic disorder characterized by premature fusion of skull sutures.
- Understanding early skull development in Apert syndrome is crucial for diagnosis and management.
Observation:
- Analysis of skull radiographs and CT scans from 16 infants with Apert syndrome (age < 1 year).
- Evaluation of dry skulls and literature cases provided additional data.
- Methods included plain radiographs, roentgencephalometry, CT scans, and 3-D reconstructions.
Findings:
- Premature coronal suture closure with a characteristic bone condensation line was observed in all infants.
- A wide midline calvarial defect, extending from glabella to posterior fontanelle, was present.
- The calvaria was hypomineralized, with bony islands in the midline defect which closed by 2-4 years without proper suture formation.
- Normal metopic, sagittal, and coronal sutures were absent; lambdoidal sutures were normal.
- Early fetal growth inhibition in the sphenofrontal and coronal suture areas is suggested.
Implications:
- The Apert skull's midline defect accommodates brain growth in infancy, despite cranial distortion.
- Absence of normal suture formation highlights the pervasive nature of the disorder.
- Findings suggest the critical timing of growth inhibition occurs very early in fetal development.
Abstract:
The purpose of the paper is to describe and analyze the infant Apert skull with emphasis on the calvaria and its early postnatal development. Skull radiographs of 16 Apert syndrome patients were examined (12 American, 4 Danish; 8 males, 8 females). The criterion for inclusion in the study was that the first skull film had to be obtained before 1 year of age. Study methods employed included plain skull radiographs, roentgencephalometric films in several projections, CT-scans, and 3-D reconstructions. Data from 2 dry skulls and 2 early cases from the literature were also evaluated The following findings were common to all cases during early infancy (less than 3 months): The coronal suture area was prematurely closed and was represented by a bone condensation line beginning at the cranial base, extending upwards, and having a characteristic posterior convexity. Anterior and posterior fontanelles were widely patent. The midline of the calvaria had a gaping defect which extended from the glabellar area to the posterior fontanelle via the metopic suture area, anterior fontanelle, and sagittal suture area. Bony islands of varying sizes were observed in the midline defect. The calvaria was hypomineralized. During the first 2-4 years of life, the midline defect was obliterated by coalescence of the enlarging bony islands without evidence of any proper formation of sutures. The calvaria became thicker with time and several cases developed increased digital markings and enlargement of the sella turcica. During infancy, the Apert skull with its gaping midline defect appears to permit adequate accommodation of the growing brain, albeit distorted in shape. Normal metopic, sagittal, and coronal sutures with interdigitations were not observed in a single instance; in contrast, the lambdoidal sutures appeared normal in all cases. The invariable findings of an extremely short squama and orbital part of the frontal bone together with the posterior convexity of the coronal bone condensation line suggest that growth inhibition in the sphenofrontal and coronal suture area has its onset very early in fetal life.