Objective: The purpose of this study is to develop an experimental spinal cord injury spasticity model using rabbits and to evaluate a quantitative spasticity measure.

Method: After an general anesthesia, 19 rabbits out of total 24 rabbits were laminectomized posteriorly and the spinal cords contused with 15 g⁓20 cm weight drop around 11th and 12th thoracic cord. After two weeks, behavioral analysis and clinical measurements of hindlimb spasticity were assessed. After that, rabbits' triceps surae was dissected and the length-tension plot was obtained by stretching it 5 mm, 2 mm/sec. And then the stiffenss of stretch reflex was determined from the length-tension plot. The stiffness of stretch reflex of the five normal control group was measured.

Results: 1) The measure was possible among 15 out of 19 spinal cord injured rabbits. One out of 19 rabbits was died

from urinary infection. Two rabbits was died from intraop-

erative bleeding at 2 weeks. Another one was excluded from the measurement due to joint contracture. 2) All of 15 rabbits showed clinical spasticity of hindlimb in 2 weeks. The spasticity was increased after the 4th day. 3) On the length-tension plot, the stiffness of stretch reflex of 15 rabbits significantly increased more than that of 5 normal group. 4) The total stiffness is correlated with the deep tendon reflex of knee and muscle tone of ankle. The stiffness of stretch reflex is weakly correlated with the deep tendon reflex of knee, digital hyperreflexia and ankle clonus.

Conclusion: The experimental spinal cord injury model and the quantitative spasticity measure method would contribute to measure the effect of the new therapy of spasticity more accurately, and to establish a principle of the new therapy. In addition, the study is expected to contribute to establish pathophysiology of spasticity. (J Korean Acad Rehab Med 2002; 26: 37-45)

The evaluation of peripheral nerve disorders has traditionally relied on clinical history, physical examination, and electrodiagnostic studies. The electrodiagnostic study is currently most popular procedure. The purpose of this study is to assess the significance of the changes of amplitude and area of compound muscle action potentials(CMAPs) in peripheral nerve injury. After compression of sciatic nerve in 65 Korean house rabbits, the amplitude and the area of CMAPs were compared to each other before and after compression injury.

The correlation coefficients between the changes of the parameters, amplitude and area, were obtained at a scheduled interval, and the parameters were also assessed when the evidence of denervation and regeneration was seen. In addition, the relationship between the degree of abonormal spontaneous activities and each parameter was assessed.

At preinjury state, there was a significantly high correlationship between two parameters. The correlation coefficients were 0.764 and 0.756 with distal and proximal stimulations respectively in abductor hallucis recordings, and 0.649 in gastrocnemius recording. At postinjury, there was more significant high correlationship between two parameters. The correlation coefficients were 0.955 and 0.962 with distal and proximal stimulations respectively in abductor hallucis recordings, and 0.930 in gastrocnemius recording. Nineteen cases showed denervation activities at postinjury 4th day. Of those cases, the amplitude was decreased earlier in 2 cases and the area in 3 cases at the same day. Of 10 cases regenerated, the amplitude was normalized earlier than the area in 2 cases. There was a significant decrement tendency in both amplitude and area with the degree of abnormal spontaneous activities.

Therefore, both the amplitude and the area of CMAPs are good quantitative indices of peripheral neuropathy and useful parameters in long-term follow up study.

The evaluation of peripheral nerve disorders has traditionally relied on clinical history, physical examination and electrodiagnostic studies. The electrodiagnostic study is currently the most popular procedure to analyse the nerve lesion, but it is painful and its result is operator dependent. The purpose of this study is to evaluate the significance of MRI signal change of denervated muscle in peripheral nerve as an adjuvant study of electrodiagnostic study. After the compression of sciatic nerves in 20 rabbits and severance of scitic nerve in 10 rabbits, the signal change of both T1WI(TR; 450 msec, TE; 15 msec) and T2WI(TR; 3,000 msec TE; 90 msec) of calf muscles were compared with EMG findings of the same muscles. Signal intensity ratio(SIR) of calf muscles was measured and compaired with the grade of abnormal spontaneous activity in the same muscles in needle EMG study. Serial studies were done on 4th day, 1 week, 2 weeks, 3 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks after sciatic nerve injury. Among 25 rabbits showing abnormal spontaneous activity in needle EMG, the signal intensity of both T1WI and T2WI was increased in 13 rabbits. The signal intensity began to increase at 1 week in 10 rabbits and 2 weeks in 3 rabbits following nerve injury which was about 1 week later than appearance of abnormal spontaneous activity in needle EMG study. There were no signal intensity increase in rabbits which showed no abnormal spontaneous activity in needle EMG study. The signal intensity ratio and grade of abnormal spontaneous activity had a good correlation(Spearman's correlation coefficiency : 0.635). The signal intensity of 3 rabbits which showed regeneration evidence in needle EMG study returned to normal. These findings suggest that MRI study of denervated muscle can be used as an evaluation method for severe peripheral nerve injury, howeverits value is doubtful in mild peripheral nerve injury.