Dandy-Walker like malformation in a Fischer-344 rat

Area of Science:

• Neuroscience
• Developmental Biology
• Comparative Pathology

Background:

• Spontaneous malformations in animal models offer insights into human developmental disorders.
• Cerebellar malformations can lead to significant neurological deficits.
• The Dandy-Walker malformation is a congenital condition affecting brain development.

Purpose of the Study:

• To describe a unique case of spontaneous cerebellar malformation in a young rat.
• To compare the observed malformation with known human conditions, specifically Dandy-Walker malformation.
• To explore potential pathological mechanisms underlying the observed cerebellar defect.

Main Methods:

• Gross pathological examination of a 32-day-old male Fischer 344 rat with observed neurological abnormalities.
• Histopathological analysis of cerebellar and surrounding brain tissue, including assessment of cellular infiltration and glial response.
• Comparative analysis of gross and microscopic findings with established descriptions of Dandy-Walker malformation.

Main Results:

• A spontaneous cerebellar malformation characterized by vermis defect and a dilated fourth ventricle was identified.
• Cerebellar hemispheres showed asymmetry, with the left smaller than the right.
• Degenerative and inflammatory lesions, including immune cell infiltration, calcifications, and astrogliosis, were noted near the cerebral aqueduct.
• Hyperplastic ependymal cells were observed in the medulla oblongata beneath the fourth ventricle.

Conclusions:

• The observed rat cerebellar malformation shares gross pathological features with human Dandy-Walker malformation.
• Degenerative and inflammatory processes adjacent to the cerebral aqueduct may play a role in the pathogenesis of this malformation.
• This case highlights the utility of rodent models in studying congenital brain anomalies and their underlying mechanisms.