Atelencephalic microcephaly in a 21-week human fetus.

Area of Science:

• Neuroscience
• Developmental Biology
• Pathology

Background:

• Atelencephalic microcephaly is a rare congenital disorder characterized by absent or dysplastic telencephalic derivatives.
• Aprosencephaly is a more severe form involving the diencephalon, potentially with holoprosencephalic facies.
• Extracranial anomalies can accompany both conditions.

Purpose of the Study:

• To describe the seventh and youngest reported case of atelencephalic microcephaly in a 21-week female fetus.
• To analyze the morphological and histological features of the brain malformation.
• To discuss the potential timing and etiology of the encephaloclastic event.

Main Methods:

• Case report of a 21-week fetus diagnosed with severe cranial malformation via ultrasound.
• Gross morphological examination of the brain and cranial structures.
• Light microscopy analysis of forebrain tissue to identify dysplastic changes.

Main Results:

• The specimen exhibited fused hemispheres, absent gyri, olfactory bulbs/tracts, and dysplastic forebrain changes.
• Ventricles were absent, germinal matrix-like cells were prominent, and pyramidal tracts were missing.
• Caudal brain structures showed mild deformation, and an ossified mass occupied the middle cranial fossa.

Conclusions:

• The observed brain abnormalities are consistent with a destructive encephaloclastic process.
• The insult in atelencephaly likely occurred after rostral neuropore closure, while aprosencephaly may result from earlier damage.
• The etiology of atelencephaly and aprosencephaly is presumed to be heterogeneous.