Aberrant supracallosal longitudinal bundle: MR features, pathogenesis and associated clinical phenotype

Area of Science:

• Neuroimaging
• Developmental Neuroscience
• Genetics

Background:

• Malformations of the corpus callosum (CC) can impact cognitive function.
• Intellectual disability (ID) is a complex neurodevelopmental condition.
• Understanding rare brain anomalies is crucial for diagnosing and managing ID.

Purpose of the Study:

• To characterize the MRI and structural features of a unique CC malformation.
• To investigate the association between this anomaly and intellectual disability in young patients.

Main Methods:

• Conventional MRI and Diffusion Tensor Imaging (DTI) were used to study subjects.
• Clinical evaluations, chromosomal microarray (CGH-array), and instrumental analyses were performed.
• Tractography was employed to visualize the aberrant bundle's orientation and connections.

Main Results:

• Fifteen subjects with a supracallosal bundle were identified among 85 patients with CC malformations.
• The CC showed variations including thickening, thinning, or a ribbon-like appearance.
• The supracallosal bundle displayed an antero-posterior orientation, bifurcating towards the hippocampi; all patients had intellectual disability.

Conclusions:

• The supracallosal bundle is an aberrant longitudinal structure detected above the corpus callosum.
• Its presence is consistently associated with varying degrees of intellectual disability.
• This bundle is hypothesized to be a persistent remnant of the fetal dorsal fornix.