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"Hydrocephalus-parkinsonism complex": progressive hydrocephalus as a factor affecting extrapyramidal tract
Shizuo Oi1, Dong Seok Kim, Mitsuru Hidaka
1Division of Pediatric Neurosurgery, Department of Neurosurgery, Jikei University School of Medicine, 3-25-8 Nishi Shinbashi, Minato-ku, 105-8461 Tokyo, Japan. shizuo.prof.oi@jikei.ac.jp
Objective:
To experimentally clarify the symptomatological and pathophysiological aspects of a newly proposed clinical entity, we produced an experimental rat "hydrocephalus-parkinsonism complex" model.
Methods:
A total of 60 male Sprague-Dawley rats were used. Twenty rats were treated with only kaolin as controls. Hemiparkinsonism was induced in the other 40 rats by stereotactic injection of 6-hydroxydopamine (6-OHDA) directly into the right substantia nigra. Twenty of these 40 rats were then treated with an injection of kaolin into the cisterna magna 3 days after the induction of parkinsonism. Neurological features were assessed weekly for 1 to 6 weeks after 6-OHDA injection by an apomorphine-induced turning test.
Results:
The mortality rate was 25% in the rats injected with kaolin and 10% in those with the 6-OHDA injection. The frequency of the induction of parkinsonism-like signs was minimal in the first 2 weeks and reached a maximum point 4 weeks after the 6-OHDA injection. In contrast, the rats injected with both 6-OHDA and kaolin developed hemiparkinsonism-like signs in the early stage of the progression of hydrocephalus, and the peak incidence was reached in the 2nd week after induction ( p<0.05 compared with the 6-OHDA group). The severity of the neurological disturbance was also significantly more prominent in the latter group.
Conclusion:
These results suggest that the hydrodynamic effect in the early period of ventriculomegaly is the mechanism for signs of parkinsonism in 6-OHDA-treated rats. It could be concluded that the hydrocephalic state aggravates parkinsonism, if any as the associated condition, and it may be a new clinical entity of hydrocephalus symptomatology with a specific pathophysiology.