A topographical analysis of encephalocele locations: generation of a standardised atlas and cluster analysis

Abstract

ObjectiveEncephaloceles are considered to result from defects in the developing skull through which meninges, and potentially brain tissue, herniate. The pathological mechanism underlying this process is incompletely understood. We aimed to describe the location of encephaloceles through the generation of a group atlas to determine whether they occur at random sites or clusters within distinct anatomical regions. MethodsPatients diagnosed with cranial encephaloceles or meningoceles were identi ed from a prospectively maintained database between 1984 and 2021. Images were transformed to atlas space using non-linear registration. The bone defect, encephalocele and herniated brain contents were manually segmented allowing for a 3-dimensional heat map of encephalocele locations to be generated. The centroids of the bone defects were clustered utilising a K-mean clustering machine learning algorithm in which the elbow method was used to identify the optimal number of clusters. ResultsOf the 124 patients identi ed, 55 had volumetric imaging in the form of MRI (48/55) or CT (7/55) that could be used for atlas generation. Median encephalocele volume was 14704 [IQR 3655-86746] mm 3 and the median surface area of the skull defect was 679 [IQR 374-765] mm 2 . Brain herniation into the encephalocele was found in 45% (25/55) with a median volume of 7433 [IQR 3123-14237] mm 3 . Application of the elbow method revealed 3 discrete clusters: 1) Anterior skull base (22%; 12/55), 2) Parieto-occipital junction (45%; 25/55) and 3) Peri-torcular (33%; 18/55). Cluster analysis revealed no correlation between the location of the encephalocele with gender [χ 2 (2, n = 91) = 3.86, p = 0.15]. Compared to expected population frequencies, encephaloceles were relatively more common in Black, Asian and Other compared to White ethnicities. A falcine sinus was identi ed in 51% (28/55) of cases.Falcine sinuses were more common [χ 2 (2, n = 55) = 6.09, p = 0.05] whilst brain herniation was less common [χ 2 (2, n = 55) = .16.24, p < 0.0003] in the parieto-occipital location. ConclusionThis analysis revealed three predominant clusters for the location of encephaloceles, with the parietooccipital junction being the most common. The stereotypic location of encephaloceles into anatomically distinct clusters and the coexistence of distinct venous malformations at certain sites suggests that their

A non-coding insertional mutation ofGrhl2causes gene over-expression and multiple structural anomalies including cleft palate, spina bifida and encephalocele

“…Encephaloceles are typically classified by rostro-caudal location with occipital encephalocele being most common ( 54 ). Anterior sub-types, such as frontoethmoidal and interfrontal encephalocele, represent a minority of cases in Western Europe and USA but are more frequently represented in South-East Asia ( 55 , 56 ).…”