A three-dimensional morphological analysis of isolated metopic synostosis
Phenotypic morphological differences were quantified three-dimensionally among individuals with untreated isolated metopic synostosis and between those individuals and similar aged normals to test two hypotheses: first, that the dysmorphology of metopic synostosis is a self-correcting condition; second, that a lack of vertical growth of the head produces that dysmorphology.
Three-dimensional (3D) coordinates were recorded for 23 craniofacial landmarks from CT scans of 15 trigonocephalic patients and of 2 normal dry skulls. The patient population was diagnosed with trigonocephaly at The Johns Hopkins Medical Institutions in Baltimore, Maryland or Children’s Hospital in Saint Louis, Missouri. The ages for the clinical sample ranged from 5 to 32 months. Three developmental age groups were constructed: (1) 5 months (N= 5); (2) 14 months (N=6); and (3) 32 months (N= 4) groups. The dry skulls were assigned the ages of 12 and 35 months according to tooth eruption patterns.
Comparisons between the metopic age groups indicate that the trigonocephaly phenotype worsens through time. Between 5 and 14 months, the neurocranium displayed an increase in vertical growth. This was followed by a lack of vertical growth between 14 and 32 months. The face displayed a lack of vertical growth from 5 to 14 months but increased in vertical growth after 14 months. Comparisons between the two older metopic age groups and the normal skulls indicate that the trigonocephalic head is taller superoinferiorly and longer anteroposteriorly. There is also a relative narrowing of the inferior temporal region in the trigonocephalic head.
These findings enabled rejection of both hypotheses and allowed us to localize form differences between normal and trigonocephalic phenotypes. Based on these results, we suggest that the trigonocephalic phenotype worsens with age and the amount of vertical growth that produces the trigonocephalic phenotype varies throughout growth with respect to location within the skull and age.
Grant sponsor PHS; Grant number: 1 P50 DE11131-01 (JTR)
Grant sponsor PHS; Grant number: F33 DE05706-02 (JTR)
Images from this publication.
This figure shows the landmarks used in this study. They were digitized on a 3D reconstruction of a patient with isolated metopic synostosis.
This figure displays the region of growth that occurs between the early age group and late age group. Solid lines indicate regions that display siginficant increases in growth through time while dotted lines indicate regions of significant decreases in growth through time.