Little evidence of association between severity of trigonocephaly and cognitive development in infants with single-suture metopic synostosis

Premature fusion of the metopic suture occurs in approximately 1 in 15 000 live births and causes characteristic head shape and facial differences, including trigonocephaly, an increased ratio of interparietal to intercoronal distances, a frontal midline ridge, and hypotelorism (Figure 1).1–4 Except when these characteristic abnormalities are mild, diagnosis of metopic synostosis generally leads to craniofacial reconstructive surgery. This surgery is usually performed within the first year of life, which normalizes head shape, increases intracranial volume, and therefore minimizes the risk of sequelae such as elevated intracranial pressure.5 FIGURE 1 Volumetric reformations of the cranium of a patient diagnosed with isolated metopic craniosynostosis. A related concern is whether children with isolated metopic synostosis may be at risk of developmental delays or deficits. Although many of the studies designed to address this long-standing question have had methodological flaws, a synthesis of current evidence suggests that the majority of children with isolated metopic synostosis perform within intellectual norms, but that the condition is associated with increased risk of cognitive, speech, language, or behavioral problems.6–16 Several possible mechanisms could account for this association, including chronically increased intracranial pressure and functional neurological problems caused by alterations in brain structure such as those noted in children with metopic synostosis.17 Alternatively, developmental deficits might arise from the same cause(s) as metopic synostosis, such as a genotype that independently influences the risk of both developmental delay and premature suture fusion.15 To provide evidence that may help distinguish among these possible mechanisms and to identify a possible predictor of developmental delay in children with metopic synostosis, we addressed the hypothesis that the severity of trigonocephaly in metopic synostosis patients is quantitatively associated with their pre- and postoperative mental and motor developmental test scores in the first 3 years of life. Previous evaluations of child development in relation to severity of metopic synostosis incorporated only qualitative or subjective, semiquantitative assessments8,10,13 or one aspect of cranial shape, the ratio of interparietal to intercoronal distances.7,12,16 We conducted a cross-sectional and longitudinal study as part of a larger, multicenter investigation of children with single-suture craniosynostosis. To quantify severity of trigonocephaly, we applied the recently described trigonocephaly severity index (TSI), which incorporates data regarding the outline of a cranial shape extracted from 3-dimensional (3D) computed tomography (CT) images.18 We showed in a previous study that the TSI distinguished metopic synostosis patients from nonsynostotic control infants with 96% accuracy.18