Technical note: A new model for quantitative analysis of brain oedema resolution into the ventricles and the subarachnoid space

Objective. The aim of the current study was to develop an experimental anim al model for quantitative analysis of oedema resolution via the subarachnoi d space and the ventricular system using fluorescent oedema markers. Methods. Artificial cerebrospinal fluid (CSF) containing TRITC-albumin (MW 67.000D) and Na+-fluorescein (MW 376D) was continuously infused into the wh ite matter of the left frontal lobe of New Zealand white rabbits (n = 6) at a rate of 100 mu l/h for 3 hrs. A closed cranial window for superfusion of the brain surface with artificial CSF fluid (3 ml/h) was implanted above t he left parietal cortex for measurement of the fluorescence markers in the subarachnoid space. Uptake of the fluorescence indicators into the ventricl es was quantified by ventriculo-cisternal perfusion (3 ml/h). The effluates were collected at 30 min intervals for 3 hrs after the start of infusion. Clearance of the oedema fluid into the perfusates was measured by fluoresce nce spectrophotometry. Results. At an intracranial pressure of 15.0 +/- 1.7 mm Hg (mean +/- SEM) b oth indicators started to accumulate in the subarachnoid and ventricular pe rfusates at 90 min following onset of oedema fluid infusion. The concentrat ions of the indicators in the ventricular system increased to 7.7 +/- 5.1% of Na+-fluorescein and 16.1 +/- 13.0% of TRITC-albumin of the total amount infused were recovered in the ventricular system at 3 hours after start of the oedema infusion, while 3.4 +/- 3.2% of Na+-fluorescein and 3.7% +/- 3.2 of TRITC-albumin, respectively, were found in the effluates of the subarac hnoid space. Conclusion. The present study demonstrates that resolution of vasogenic bra in oedema into the cerebral ventricular system and the subarachnoid space f ollowing its entry into cerbral whits matter can be quantitatively analysed using fluorescence markers, which serve as oedema fluid indicators. The re sults indicate that the oedema fluid is cleared not only into the ventricul ar system but also via the subarachnoid space.