| Objective:Traumatic brain injury(TBI) is common in neurosurgery and is associated with high disability rate, morbidity, and costs to society. TBI can be classified according to the nature of the physical injury, the type of pathology, and the severity of impaired consciousness and neurological function. Guidelines have been formulated for management and when followed lead to improved outcomes. Further work is needed for improved prognostic determination in the early phases. A decompressive craniectomy(DC) is a procedure that removes a piece of the skull and cuts open the dura to relieve high intracranial pressure and mass effect from swelling. Once intracranial pressure has normalized and the patient has recovered, the bone is replaced in a delayed fashion(usually 1–3 months after the initial procedure). Well-designed studies favor the use of decompressive craniectomy for malignant swelling after a large stroke, but decompressive craniectomy in the setting of trauma remains controversial. This study applied “free-fall-weight hit” model of TBI by which CD1 mice model was established, using mice neuroethology raters and a series of neurobehavioral tests after TBI and DC to observe behavioral changes over time, and trying to clarify the molecular mechanism, to provide experimental basis for the clinical treatment of traumatic brain injury and skull repairing to choose the best time. The brain water content was quantitied as a measure of the brain edema.Methods:Totally 75 CD1 mice were randomly divided into normal control group, TBI group, TBI + DC group, which were all clean and adult male with the weight of 35g-45 g. “free-fall-weight hit” model was adopted to establish the TBI group. 15 mice were classified into the normal control group, undertaking no operation and accepting regular breeding. 30 mice were in TBI group of “free-fall-weight hit” model which was operated as follows. First, we cut head skin of mice to expose the left parietal bone. Then head of mice was to be fixed on hard metal floor in a exposed skull’s parallel position to the floor. A cylindrical metal weighting 10 g freely fell to hit the exposed skull from height of 25 cm in an organic glass tube which is slightly larger in diameter. Rebouncing injury should be avoided. After above process, suture were essential. There were 30 mice in TBI+DC group, which took the above TBI process first and decompressive craniectomy operation after 4-6 hours completed by micro drill and microscope. 5 same mice in every group were rated by neuroethology human raters after respective intervention’s 1 hour, 24 hours, 7 days, 14 days, 21 days, 28 days. Every group went through open field test before and after respective intervention’s 7 days, 14 days, 21 days, 28 days except normal control group. Every group went through the elevated plus maze after respective intervention’s 14 days, 28 days and barnes maze after respective intervention’s 28 days. Measure the water content of brain by wet and dry weight method. Each 3 mice in every group were put to death to weigh wet brain after respective intervention’s 12 hours, 1 day, 3 days, 5 days, 7 days. Dry weight was measured after another 48 hours at 65℃ oven except normal control group. Immunohistochemical method was adopted to observe gfap and neun antibodies’ expression in each group’s mice cerebral cortex. Each 5 mice in every group were put to death before being perfusing by Paraformaldehyde and carried out the immunohistochemical experiment after respective intervention’s 7 days, 14 days, 28 days. Analysis images by pathology image analysis system of image processing software image-pro plus 6.0. Use SPSS 21.0 software to obtain statistical data and then observe the changes in cerebral cortex.Results: 1 general observation: Experimental groups(TBI group and TBI+DC group) mice behaved in loss of appetite and motor and in drowsiness after revival from anesthesia and recovered slightly after intervention’s 1 week, however, worse than normal control group. Normal control group’s mice ate and drank smoothly in a good mental state with flexible extremities. 2 behavioral experiments 2.1 NSS score: There were different NSS trends among three groups over time. TBI group and TBI+DC group overlapped comparising in average, both of which scored more than normal control group with statistical difference(P<0.05). The mean sequence is TBI group>TBI+DC group at 1h,24 h,7d,14 d,21d and TBI group<TBI+DC group at 28 d. 2.2 Open field test 2.2.1 The overall average velocity: There existed no statistical difference(P>0.05) between 2 groups with apparent decrease in TBI group after intervention and slight increase beyong 14 days. Also there were downtrends in TBI+DC group with a in-between plateau. The mean sequence is TBI group<TBI+DC group at 7d,14 d,21d and TBI group>TBI+DC group at 28 d. 2.2.2 The central regional activity time: There existed no statistical difference(P>0.05) between 2 groups with apparent decrease in TBI group after intervention and slight increase beyong 21 days. There was a consistent decline in TBI+DC group with a point of intersection with TBI group at about 21 days. 2.2.3 The corner regional activity time: There existed no statistical difference(P>0.05) between 2 groups with apparent increase in TBI group after intervention and slight decrease beyond 14 days. The TBI+DC group ascended along time below TBI group with a slight change after 14 days. The mean sequence is TBI group>TBI+DC group at 7d,14 d,21d and TBI group<TBI+DC group at 28 d. 2.3 Elevated plus maze 2.3.1(1) Total numbers into the arm at 14 th day: There existed statistical difference among 3 groups(P<0.05)while TBI group and TBI+DC group exceeded normal control group without statistical difference between them.(2) Numbers into open arms at 14 th day: There was no statistical difference(P>0.05) among groups.(3) Numbers into close arms at 14 th day: There existed statistical difference(P<0.05) among 3 groups while mean decreased successively in TBI group, TBI+DC group and normal control group. 2.3.2(1) Total numbers into the arm at 28 th day: There existed statistical difference(P<0.05) among 3 groups while TBI group and TBI+DC group exceeded normal control group without statistical difference between them.(2) Numbers into open arms at 28 th day: There existed statistical difference(P<0.05) among 3 groups while TBI group and normal control group exceeded TBI+DC group without statistical difference(P>0.05) between them.(3) Numbers into close arms at 28 th day: There existed statistical difference(P<0.05) among 3 groups while mean decreased successively in TBI+DC group, TBI group and normal control group. 2.4 Barnes maze The total number of errors and time to find the target: Statistical differences existed given an overall comparison of all groups(P<0.05). Mean decreased successively in TBI+DC group, TBI group and normal control group. 3 Wet and dry weight:Statistical differences existed on brain water content on the whole(P<0.05). The mean curve was in unimodal shape and the max value was 3d’s. TBI+DC group was inferior to TBI group on left brain water content and there was little difference between right side. 4 Immunohistochemistry(IHC) 4.1 Glial fiber acidic protein(GFAP): Statistical differences existed on positive cells among groups on the whole(P<0.05). TBI group’s value was the sequence by 7d>14d>28d. TBI+DC group’s lowest point was at 14 d. There was little change in normal control group over time. 4.2 neuron-specific nuclear protein(Neun) : Statistical differences existed on positive cells among groups on the whole(P<0.05). Both TBI group and TBI+DC group declined along time with TBI+DC group above TBI group at 7th day. The two group overlapped partly at 14 th day. TBI group exceeded TBI+DC group at 28 th day. There was little change in normal control group over time.Conclusions:1 The “free-fall-weight hit” model provides an effective model to mimic some of the pathologic and behavioral changes of TBI.2 TBI obviously damage the cognitive and motor ability of CD1 mice. DC can reduce the damage before 21 d but increase the damage at 28 d.3 TBI obviously increase the anxiety level of CD1 mice. DC relief the anxiety at 14 d but increase the anxiety at 28 d.4 Both TBI and DC impair the spatial memory of CD1 memory at 28 d.5 TBI obviously cause the brain edema of CD1 mice which is alleviated by DC and the peak is at 3d.6 TBI obviously cause the cerebral cortex inflammation and neuronal death of CD1 mice. The degree of inflammation:7d>14d>28d. The inflammation is gradually alleviated at 7d,14 d after DC but is aggravated at 28 d. The neuronal death number sequence is TBI group>TBI+DC group at 7d and TBI group<TBI+DC group at 28 d with little difference at 14 d.To sum up, decompressive craniectomy has therapeutic effect for CD1 mice’s traumatic brain injury at early stage and skull defect does no good to neural functional recovery after 4 weeks. |
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