gms | German Medical Science

Objective: Methods reported to date for penetrating the cerebrospinal fluid (CSF) containing subarachnoid (SA) space of small experimental animals have always entailed the use of stiff or relatively stiff catheters. In the present study, a less traumatic tapping procedure is described, which installs and maintains a catheter in the middle cranial fossa (MCF) of the rat for repeated use for an extended period of at least two weeks. The novel approach described was well tolerated by the animals. It has proved adequate for the repeated application of substances into the MCF.

Methods: After bore-hole trepanation at the os interparietale of Wistar rats and opening of the dura, the subdural/subarachnoid space was stretched by means of a saline injection. Like a cardiac catheter, the thin intracranial part of the extracted polyurethane catheter glided on the liquid film into the MCF between the cerebellum and cerebrum at the rostral petrosal bone edge. The intracranial part of the catheter had a lumen of about 70 µm and an external diameter of about 100 µm. The catheter was fixed by means of tissue adhesive in the bore-hole, and closed by means of a mandrin.

Results: The catheter was implanted in 27 animals. In 24 animals, the position of the catheter was regular in the subdural/subarachnoid gap in the MCF with subarachnoid distribution of injected test substances. The animals were not impeded by the catheter, and they were free of post-operative clinical findings. Catheters of 16 animals with daily rinsing remained freely permeable until the 15^th post-operative day (POD). In eight animals the catheter was rinsed once per week; of these it remained open in four animals until the 21^st POD, was removed from two animals on the 16^th or 20 POD, and clogged in two animals on the 21^st POD. In animals retaining the catheter until killing, it was found in a correct position without any macroscopic visible alteration of the brain tissue or blood vessels. Three animals developed fateful complications such as bleedings or mispositioning.

Conclusions: The animals obviously were not impaired by the catheters, even when the latter remained for weeks. The catheter is positioned in such a way that it could not be removed by the rat. Safe access to the SA space in the MCF is possible. The catheter was permeable for the desired period of time, so that e.g. repeated drug application is possible. If carefully positioned, brain tissue and blood vessels are not altered.