Intracranial Irregularities Beside Hydrocephalus in H-Tx Rats
It has been well documented that up to 70% of H-Tx rats’ offspring suffer from severe hydrocephalus, which can be fatal if it remains untreated. Some offspring also have non-fatal moderate hydrocephalus allowing a normal life expectancy. The objective of
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Abstract Introduction It has been well documented that up to 70% of H-Tx rats’ offspring suffer from severe hydrocephalus, which can be fatal if it remains untreated. Some offspring also have non-fatal moderate hydrocephalus allowing a normal life expectancy. The objective of this study was finding other morphological intracranial abnormalities that are not directly related to hydrocephalus. Method An MRT for small animals (Bruker, Biospec, Erlangen Germany) with a 2.4 T magnet at 100 MHz has been used to study 98 apparently non-hydrocephalic H-Tx rats. T2-weighted 2D-RARE, T2-weighted 3D-Turbo-RARE sequence and T1-weighted 3D-gradient-echo sequences were used. Results Apart from 36% of animals with moderate or mild hydrocephalus, we found one animal with a cystic cerebellar malformation similar to an arachnoid cyst with minimal space occupying effects. Nine rats had a mild or moderate-sized unilateral enlargement of one lateral ventricle, but a causative occlusion of the Foramen of Monroe could not be verified. Finally, one animal with huge hydrocephalus had a midline cystic malformation between both cerebral hemispheres. Conclusion Aside from the well-documented hydrocephalus, H-Tx rats may develop other intracranial malformations that have not yet been documented in the literature. Keywords Hydrocephalus • H-Tx rats • arachnoid cyst • unilateral hydrocephalus • midline cyst • midline malformation
M. Kiefer (*) Departments of Neurosurgery, Saarland University Medical School, Kirrberger Street, Building: 90.1, Homburg-Saar 66421, Germany e-mail: [email protected] G. Schneider Department of Diagnostic and Interventional Radiology, Saarland University Medical School, Kirrberger Street, Building: 90.1, Homburg-Saar 66421, Germany R. Eymann Department of Neurosurgery, Medical School, Saarland University, Kirrberger Street, Building 90, Homburg-Saar, Saarland 66421, Germany
Introduction H-Tx rats typically have inherited hydrocephalus with ventricular dilatation starting in late gestation due to obstruction of the cerebral aqueduct (7,13). Depending on environment, parity and other factors (5), the frequency of severely affected pups varies between 15% and 70% (11,13), which is compatible with the mode of inheritance of hydrocephalus (5). Untreated severely affected rats die from intracranial pressure excess at 4–6 weeks of age. Severely affected animals suffer from non-communicating hydrocephalus due to aqueduct stenosis normally, but some cases with probably different underlying pathology may occur (1, 25). While a milder hydrocephalus form characterized by a later onset occasionally occurred in a colony maintained in Florida (USA) (5), others have found higher frequencies of moderate hydrocephalus in their colonies. A colony maintained in Japan was found with 5% and 14% moderate, compensated and mild hydrocephalus, respectively (20,23,27). The incidence of mild and moderate hydrocephalus, allowing long-term survival without treatment, was 36% in our colony. The outer skull appearance allows the identifica
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