The Third Ventricle in Kaolin‑induced Hydrocephalus in Juvenile Rats

Abstract

Background: The enlargement of the third ventricle in hydrocephalus has mechanical effects on the structures that form its boundaries such as thalamus and hypothalamus. This may explain some of the symptoms associated with hydrocephalus. While the lateral ventricles had been widely investigated in hydrocephalus, studies of the third ventricle are sparse. The present study set out to investigate the ependymal lining and the direction of enlargement of the third ventricle in hydrocephalus.
Materials and Methods: Three-week old rats were divided into 6
groups (A‑F) of five each. Groups A‑C were experimental and sacrificed after 1, 4, and 8 weeks of induction, respectively, while groups D‑F served as age‑matched controls. Hydrocephalus was induced by intracisternal injection of 0.04 ml of 200 mg/ml kaolin suspension. Rats were sacrificed by cervical dislocation and approximately 1 mm thick coronal brain slices were obtained at optic chiasma level. Slices were fixed in 10% formal saline, processed and stained with hematoxylin and eosin.
Results: Compared with corresponding control rats, the lateral ventricle width was significantly increased in 1 and 8 weeks postinduction experimental rats (P = 0.005 and 0.012 respectively), while supero‑inferior distance of the experimental third ventricle was significantly lower at 1‑week postinduction (P < 0.001), and increased at 8‑week postinduction (P = 0.025). However, differences in the inter‑thalamic distance at 1‑ and 8‑week were not statistically significant (P = 0.14 and 0.224, respectively). Ependymal detachment was patchy and generalized at 1 and 4 weeks, respectively. Thinned and detached ependymal lining were noted 8‑week postinduction.
Conclusion: Kaolin-induced hydrocephalus caused early ependymal detachment in the third ventricle of rats, while ependymal thinning and villi sparing was a feature of chronicity. The third ventricle enlarges in the supero-inferior direction, this might explain some symptoms associated with hydrocephalus.