Defining the Normal Range of Forehead Convexity in Infants: Moving Toward an Objective Diagnosis of Metopic Craniosynostosis.

Abstract

Background: Metopic craniosynostosis (MCS) presents unique diagnostic challenges. Objective measures to correctly diagnose MCS have been developed, but mostly rely on thresholds obtained through subjective clinical diagnosis. This study quantifies the spectrum of normal infant anterior cranial shapes using an entirely automated method to aid in diagnosis of MCS using population statistics.

Methods: A retrospective review of computed tomography (CT) scans from patients aged 0 to 24 months was completed. Patients with known craniosynostosis or associated syndromes, hydrocephalus, or other brain or cranial abnormalities were excluded. Optimal interfrontal angle (oIFA), transverse forehead width (TFW), skull circumference (SC), intracranial volume (ICV), and malformation range (MR) were calculated using an automated analysis pipeline.

Results: A total of 582 subjects were included. Median age at CT scan was 11.6 months. Males demonstrated significantly higher median ICV, TFW, and SC than females (P<0.001 for all). OIFA was inversely correlated with age, decreasing by approximately 8 degrees between neonates and 24-month-old children. Transverse forehead width, SC, and ICV all increased significantly over the same age range (P<0.001 for all).

Conclusion: This study provides the largest and most comprehensive evaluation of normal frontal cranial shape in infants to date. The data presented show that forehead convexity follows a normal distribution after correcting for age. These oIFA measurements were collected using an automated method, allowing analysis of forehead shape without any basis in subjective interpretation. This data provides a basis for abandoning subjective, clinical diagnosis of MCS.