Intracranial Pressure Assessments - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 376

results by incomplete transmission of supratentorial pressure to the
cisterna magna ( 17, 18 ). A cisterna magna catheter may therefore
not be suitable for ICP measurements in experimental models with
supratentorial mass lesion or cerebral swelling. Undetected CSF
leakage from the ventricle or cisterna magna may occur and lead to
decreased ICP levels ( 18 ).
The main advantage of intraparenchymal ICP measurement
with fi beroptic catheters besides its simplicity is that it is a reliable
and reproducible method. It is much easier and less time-consuming
than ventricular or cisterna magna cannulation and ICP monitor-
ing. However, cortical damage was larger in intraparenchymal
monitoring in some series caused by a bigger probe size than after
intraventricular ICP measurement. This might be a technical limita-
tion in studies in which cortical damage must be avoided. The main
advantage of intraventricular and especially cisternal cannulation is
the possibility to access CSF for additional examination. Furthermore,
using a PE tube coupled to any sensitive pressure transducer is cheaper
than specifi c intraparenchymal ICP-measurement probes.

Insertion of ICP-probe into the brain can cause injury and bleed-
ing that may evoke increase of ICP. Upon histological examina-
tion, localized tissue trauma at the site of probe insertion is
observed. Furthermore, cortical damage was more extended after
intraparenchymal monitoring caused by a bigger ICP-probe size
than after intraventricular ICP measurement ( 18 ). Care has to be
taken to avoid brainstem injury while cannulating the cisterna
magna. Venous bleeding while puncturing the membrana atlanto-
occipitalis is common. Artifi cious blood contamination may lead to
misinterpretation of experimental results.

2.2. Surgical Trauma
by Probe Implantation

2.3. CSF Sampling

In rats, CSF production rates were estimated to be 2.2 μ l/min

with a total volume of 400-550 l

can be collected via the cisterna magna ( 20 ). Therefore, minor
artifi cious blood contaminations of the CSF can strongly alter CSF
content profi les and lead to misinterpretations.

μ l ( 19 ). Usually less than 150 μ

3. Material and
Instruments

1. Stereotactic frame.
2. Micromanipulator.
3. Homeothermic blanket (Harvard Apparatus).
4. Microscope (Zeiss).

3.1. Instruments