Cytological and Cytoarchitectural Changes in the Feline Cerebral Cortex during Experimental Infantile Hydrocephalus

Abstract

While many reports have documented the effects of hydrocephalus on the ependyma and periventricular white matter, primarily in adult animal models, little is known about alterations specific to neurons. The present study has evaluated qualitatively the effects of hydrocephalus on the neurons and vasculature of the cerebral cortex in a neonatal animal model. The cisterna magna of 4 to 11-day-old kittens was injected with a solution of 25% kaolin to induce hydrocephalus. Ultrasonographic evidence of hydrocephalus was noted within 3–5 days of injection. Hydrocephalus progressed until day 18–25 postinjection when the animals were sacrificed. The cytologic and cytoarchitectural changes within the cortical mantle of affected animals were compared with control age-matched counterparts who had undergone intracisternal saline injections. Areas 4 (primary motor), 22 (association) and 17 (primary visual sensory) were examined light microscopically. Neurons from hydrocephalic brains exhibited 3 types of pathological response. Pyknotic somata were shrunken, disoriented and so hyperchromatic that neither nuclei or nucleoli could be delineated. Reactive somata were also shrunken and hyperchromatic, but nuclei and nucleoli could still be observed. Many neurons contained an abundance of vacuoles, giving their somata a flocculent appearance; these cells were termed ‘spongy’ neurons. Both normal and pathological neurons were smaller and disoriented, with a considerable decrease in neurons noted in areas 22 and 17 from severely hydrocephalic animals. The deeper cortical layers were more affected than the more superficial laminae in that more reactive and pyknotic neurons were present in layers V and VI. As the ventriculomegaly became more severe, changes could be observed in neurons within layers II and III. Furthermore, the cerebral vasculature exhibited a decrease in the number of vessels and a preponderance of profiles oriented parallel to the menin-geal surface. The severity of these effects followed a rostral to caudal gradient, such that the occipital cortex demonstrated the most damage. These results suggest that both the motor deficits and the subtle cognitive deficiencies seen with hydrocephalus may be attributed to perturbation of neuronal and vascular elements in the cerebral cortex.

Study of corpus callosum in experimental hydrocephalic wistar rats

“…Similar findings were seen by Wright et al, although in kittens 15 . Following this these animals begin to present apathy and trembling, also in the same way as hydrocephalic patients.…”

“…Following this these animals begin to present apathy and trembling, also in the same way as hydrocephalic patients. Trembling is referred to by several authors, so much so as in hydrocephalic rats as in hydrocephalic cats 8,15 .…”

“…Assumptions suggest that the development of the nonverbal functions is dependent on the integrality of the white matter in both the brain hemispheres, as well as the integrality of the commissures, especially that of the corpus callosum 14 . There are authors who attribute the cognitive deficiencies to the lesions of the vascular elements of the cerebral cortex 15 . Even with the improvement of the ventricular shunts not all the neurological and structural alterations are reverted with the treatment of the hydrocephalus.…”

Hydrocephalus and Syringomyelia in a Cat.

“…They reported that the diagnosis was made by ventriculography, but did not mention what occurred in the brain after surgery. Other reports have indicated that reconstitution of the cerebrum after shunting occurs only in the white matter [5,7,14,21,26,27]. In our case, the ventricles did not differ significantly in size at the first and forth MRI scans, but the syrinx was no longer recognizable at the fourth MRI.…”

“…Both hydranencephaly and hydrocephalus have been known to occur concurrently with parvovirus infection [13,15]. On the other hand, experimentally induced hydrocephalus becomes apparent within 1 to 2 weeks of a kaolin injection [5,7,9,10,14,21,26,27] and the central canal dilates within 2 to 6 weeks [9,10]. As regards parvovirus infection, serum IgM and IgG levels have indicated that the infection is established within 3 days to 3 weeks after contact (Unpublished information; Nikken Bio Medical Laboratory Inc., Japan).…”