The relationship between external bony defects and widened lateral interorbital distance in frontoethmoidal encephalomeningocele.

Purpose: The aim of this study was to identify the prevalence of the abnormal lateral interorbital distance (LIOD), micropthalmia or anopthalmia and incidence of hydrocephalus in frontoethmoidal encephalomeningocele (FEEM), and to identify the correlation between the external bony defects and a widened lateral orbital wall.

Materials And Methods: FEEM patients who were treated in the Faculty of Medicine, Chiang Mai University between January 1, 2006, and December 31, 2016, were retrospectively reviewed from the medical records. We included the patients who had undergone head computed tomography (CT) of the facial bones. Exclusion criteria were any patients who had undergone prior facial surgery or had maxillofacial bone trauma before they underwent a CT scan, craniofacial disease such as facial clefts, frontonasal dysplasia, craniosynostosis, and inter-frontal encephalocele. Measurements were taken from the CT images to establish the diameter of the external bony defect, medial interorbital distance and lateral interorbital distance. The relationships between the external bony defect and widened LIOD were analyzed. Patients were divided into two groups: those with normal LIOD and those with wide LIOD.

Results: A total of 94 FEEM patients were evaluated. Thirteen patients (13.83%) had a wider than normal LIOD. The incidence of micropthalmia or anopthalmia was 9.57% and hydrocephalus was 45.74%. From a univariable model, there were no statistically significant differences in terms of patient characteristics between the LIOD groups, except for sex. The proportion of wide LIOD was higher in male patients (male vs female; 20.34% vs 2.86%, p = 0.027). The proportion between the external bony defect and the LIOD (EL ratio) associated with a wide LIOD was shown in a cutoff point of 23% (AuROC = 73.27%, 95%CI = 59.87%-86.66%). The multivariable analysis indicated factors associated with abnormal LIOD were an EL ratio of 23% (adjusted RR = 1.98, 95% CI = 1.58-2.51) and male sex (adjusted RR = 6.85, 95% CI = 2.00-23.55).

Conclusion: There is an association between the EL ratio and widening of the LIOD. An EL ratio greater than 23% could be used to moderately predict a wide LIOD. A large external bony defect may be associated with lateral displacement of the orbit causing true hypertelorism. Therefore, orbital translocation must be considered in patients with a wide LIOD.