BACKGROUND: Presyrinx state of spinal cord reflect the initial lesion of syringomyelia (SM).The early trals has proved that ischamia and edema are main pathological of presyrinx state. OBJECTIVE: To estabilsh SM model of rabbits for investigating the relationship between changes of morphous and function of blood-spinal cord barrier and the edema degree, histological changes in presyrinx state of SM,and to explore the mechanism of the presyrinx state of SM.DESIGN: Randomized controlled animal experiment.SETTING: Department of Neurosurgery,Fourth Hospital,Heibei Medical University.MATERIALS: Sixty Chinese healthy white rabbits,aged 3.5-4.5 months,weighing 1.5-2.0kg,were provided by Experimental Animal Center of Hehei Medical University[certification:(SYXK(Ji)2003-0026)].Evan's blue (EB)and dimethylformamide(DMF) were purchased from Jingmei Biotech Co.,Ltd RM2125 paraffin section cutter(Leica Company,Japan),H-7500 transmission electron microscope (Hitachi Company,Japan),PM-20 light microscope photograph system(Olympus Company,Japan).METHODS:The experiment was carried out in the Laboratory of Neurosurgery Department,Second Hospital of Hebei Medical University from January to June 2006.①All the rabbits were randomly divided into two groups:model group(n=40),control group(n=20).Rabbits in two groups were divided into five subgroups once again at five time points(1st , 3rd ,7th ,14th ,21st days,n=8 and n=4 at each time point in the model group and control group,respectively).Under ketamine anesthesia,0.6 mL Kaolin solution(250 g/L,37℃)was injected into the cisterna magna of rabbits in model group,while 0.6 mL physiological saline(37℃)was injected into the rabbits of control group.②On the 1st ,3rd ,7th ,14th , 21st days after kaolin injection,cervical cord samples were harvested after sacrifice of animal. Quantitative analysis on the function of blood-spinal cord barrier was performed by Evan's blue technique.Water content of spinal cord was measured by dry-wet weighing technique.Samples were fixed in 40 g/L paraform for haematoxylin and eosin staining.Pathological and ultramicrostructural observation was carried out under a light microscope and H-7500 electron microscope,respectively.③The comparison of measurement data was performed with analysis of variance.MAIN OUTCOME MEASURES:The changes of water content.Evan's blue content and pathology in upper cervical cord of presyrinx state at different time points.RESULTS:All the 60 rabbits were involved in the result analysis.①Ultramicrostructural observation:During the whole process of occurrence and development of presyrinx state of spinal cord,no obvious morphological changes of blood-spinal cord barrier were found. Microvascular endothelial cells were in integdty in morphology, basal membrane was continuous and smooth, and the structure of tight junction was not destructed remarkably.②Water content of spinal cord:Compared with control group,the water content of spinal cord was increased on the 1st day[(68.35±0.7)%vs.(66.51±0.32)%,F=7.387,P=0.026] after kaolin injection,more prominent on the 3rd day[(72.70±0.88)%,F=123.48,P=0.000],reached its peak on the 7th - 14th day [(72.92±0.86)%,F=135.94,P=0.000;(72.18±0.55)%,F=28.18,P=0.001],and was declined slowly after 21 days[(70.03±0.77)%,F=11.51,P=0.009],but it was still higher than that of control group[(65.98±0.56)%,F=11.51.P=0.009].③Evan's blue content in spinal cord tissue:It started to rise on the 3rd day after operation[(2.79±0.42)mg/L,F=61.35,P=0.000],reached its peak on the 7th day[(3.53±0.45)mg/L,F=528.35,P=0.000],and kept this high level till the 14th day[(3.45±0.35)mg/L,F=326.57,P=0.000].It decreased on the 21st day[(3.36±0.27)mg/L],but was still higher than normal level[(1.69±0.16)mg/L,F=58.63.P=0.000].④Neurologic function score:The neurologic function score of rabbits in the model group was close to that in the control group preoperatively and on the postoperative 1st and 3rd days(F=2.667,P=0.141);Abnormal nerve function appeared on the postoperative 7th day(F=32.667,P=0.00),and the neurologic function scores were gradually decreased with the elongation of time.The neurologic function scores in the model group were significantly lower than those in the control group on the postoperative 14th and 21st days(F=42.667,34.571.P=0.00).CONCLUSION:Under the presyrinx state of spinal cord of experimental rabbits,the destruction of blood-spinal cord barrier of spinal cord and spinal edema co-exist with the same changing tendency. Although morphological integrity of blood-spinal cord barrier is kept,the function of blood-spinal cord barrier was destroyed in the early stage and permeability is increased.This functional disorder plays an important role in the occurrence and development of presyrinx state of SM.