Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
Sign up to receive an email alert when a new Case of the Week is posted.
May 20, 2021
Brain-in-Brain Malformation
- Background:
- Until now, the exact developmental mechanism and genetic pathways for this malformation have not been completely explained, mainly due to its rarity.
- Some authors suggested that brain-in-brain malformation is a variant of holoprosencephaly (HPE) because they share similar imaging findings related to prosencephalon development. If brain-in-brain is part of the HPE spectrum, especially the middle interhemispheric variant, then its embryologic pathway may share similar mechanisms like impairment of the ventralization or excessive dorsalization of the forebrain, defect of telencephalon dorsal-ventral induction, and lack of induction of the dorsal midline structures.
- Recently, brain-in-brain malformation was classified as a subtype of heterotopia with a bilateral and complex pattern. There is a case in the literature whose imaging aspects were consistent with brain-in-brain malformation and pathologic examination and immunohistochemistry revealed normal neuroglial tissue representing heterotopic brain tissue (subcortical heterotopia). Further research is needed.
- Clinical Presentation:
- Patients usually have seizures, developmental delay, normal or enlarged head size, and facial abnormalities.
- There are no syndromic associations or genetic mutations described until now.
- Key Diagnostic Features:
- Anterior midline location–mass of gray and white matter signal intensity continuous with the underlying cerebral parenchyma associated with a single ventricular cavity, usually hypoplastic
- Azygos anterior cerebral artery, fused thalami or basal ganglia usually associated
- Encephalocele, turricephaly, absent olfactory bulbs, and abnormal interhemispheric fissure were also described in the literature.
- Differential Diagnoses:
- Hamartoma: Tumorlike lesion with similar signal intensity to the cortex in all sequences; midline location is common (eg, hypothalamic).
- Microventriculy with heterotopia/aventriculy: Absent or very small lateral ventricles; unseparated midline structures (eg, thalami); no midline mass; encephaloceles can be found.
- Subcortical heterotopia: Typically unilateral and does not extend to third ventricle; similar signal intensity to the cortex in all sequences
Current Issue
Case Collections
