BACKGROUND: Whether horizontal and vertical impacts cause craniocerebral injury of the same degree, and whether serum myelin basic protein (MBP) changes is associated with the direction of impact have been scarcely addressed in previous studies.OBJECTIVE: To observe the change in the serum MBP levels and morphological changes of the brain tissue rabbits with craniocerebral injury resulting from impacts from different directions.DESIGN: A randomized controlled experiment.SETTING: Department of Neurosurgery of a hospital affiliated to a medical university.MATERIALS: This study was conducted in the Central Laboratory of Shenyang Medical College between October 2003 and January 2004. Totally 30 healthy rabbits of either sex were randomly divided into two equal groups to receive vertical and horizontal impact on the head.METHODS: All the rabbits were anesthetized and fixed in prone position onto a table equipped with a device for inducing impact on the head from different directions. Venous blood of 1 mL was taken from the edge of the ear of each rabbit for detecting MBP before injury. The rabbits in vertical impact group received the impact of a hammer falling directly on the parietal bone of the skull. In the horizontal group, the rabbits were subjected to horizontal impact on the lateral side of the skull. Forty-eight hours after the injury, venous blood were again taken for MBP measurement. The rabbits were then killed for pathological examination of the brain.MAIN OUTCOME MEASURES: Changes in serum MBP and pathomorphology of the brain tissues in the two groups after the impact.RESULTS: ① According to intention to treat analysis, all the 30 animals were involved in the experiment. There was no significant difference in serum MBP levels between the two groups before the impact, nor 48 hours after the impact( P ＞ 0.05). In the vertical impact group, serum MBP levels before the impact was( 1.68 ± 0. 86) μg/L, which was significantly lower than that after the impact[ (5.25 ± 1.96) μg/L, t = 3. 226, P ＜ 0. 05]. ② In the horizontal strike group, serum MBP also significantly increased from the level of( 1.70 ± 0.91 ) μg/L before impact to(5.73 ± 2.07) μg/L after that( t = 3. 080, P ＜ 0.05) . ③ After the impact, vasodilation and congestion in the cortex near the midline of the bilateral parietal region and edema in the deep layer of the white matter were observed in the vertical impact group, along with significant enlargement of the extravascular and extracellular space. In the horizontal group, similar changes except those near the midline of the bilateral parietal region took place after the impact; the same pathological changes were also observed in the basal plane, with nearly identical pathological changes in the deep layer of the white matter.CONCLUSION: Vertical and horizontal impacts can both result in almost identical brain injuries demonstrated by similar changes in serum MBP and the pathomorphology of the brain tissues after the impacts.