Experimental Studies on the Spinal Cord Injury: Part I: K42 Uptake of the Traumatized Canine Spinal Cord White Matter.

Choi, Sun Kil; Choi, Sang Il; Kim, Joo Myung; Choi, Duck Young; Rhim, Kwang Seh

Original Article

Journal of Korean Neurosurgical Society 1976;5(2): 29-38.

Sun Kil Choi, Sang Il Choi, Joo Myung Kim, Duck Young Choi, Kwang Seh Rhim

Department of Neurosurgery, Chung-Ang University, School of Medicine, Seoul, Korea.

ABSTRACT

The salient pathological findings following acute blunt cord trauma, now documented by a number of investigators, are hemorrhagic necrosis of central gray matter and increased catecholamine, especially dopamine concentration of the traumatized cord level, which have progressive and, according to some authors, reversible nature. But paraplegia and disappearence of sensory evoked potential (SEP) are the obvious clinical conditions appeared immediately after blunt cord trauma which are sudden events not progressive ones. These phenomena are clearly results of neuronal conduction block of white matter at the traumatized cord level. Dohrmann et al. demonstrated in their electron microscopic studies that the myelinated nerve fibers of the traumatized cord level with 300 gm-cm force are resemble those of a control animal until 15 to 20 minutes after impact. At this point, we can imagine 2 phase of pathophysiological process of acute blunt cord trauma, ie ; 1. Initial alterations of normal cord physiology. 2. Secondary or aggrevating processes to the initial alterations of normal physiology. There are a number of reports and arguements about so called secondary aggrevating processes but neither explanations nor experimental studies about those immediate pathologic clinical phenomena. As the initiation of the investigations about the immediate physiological alterations, we planned this experiment to observe radioactive potassium uptake of the white matter of the blunty traumatized spinal cord. At first, we carried dorsal laminectomy out on the T2 and T6 level of adult Mongoreal dogs and injected K42 Cl, 500 micro Ci into the right atrium via catheterized antecubital vein. At 6 seconds after injection of K42, 5cc bolus of saturated KCI was shot intravenously via same route to produce instant cardiac arrest. As rapidly as possible, the cord of T2 and T6 were excised and dissection of white matter was done which was facilitated by use of loupe. After tissue weighing, tissue indicator was counted with Well-type Scintillating Counter. As a result, the radioactivity of T6 white matter (cpm/mg) was 77% (SD=2.04) of that of T2, which was essentially same as the regional blood flow rates measured by Bingham et al. with fractional indicator technique. Secondly, we elicited seizures on the animals by electrical stimuli delivered to the electrode attached on the bifrontal scalp. Seizure duration was 3 minutes and at the time of termination of tonic phase 500 micro Ci of K42 Cl was injected. 6 seconds later cardiac arrest was produced and radioactivity of the white matter T2 and T6 were measured with same way described above. Radioactivity of the white matter of T2 and T6 were measured with same way described above. Radioactive potassium uptake of the white matter of T2 and T6 were 57.82% (SD=2.62) and 61.38% (SD=3.69) to those of control animal. This result can be explained as a greatly increased K+ ion concentration in the interstitial space of white matter during the convulsive seizure. Next time, the animals were laminectomized on the level of T2 and T6, and 500 gm-cm force was impacted on the T6 exposed cord while T2 segment served as non-traumatized control. 15 minutes after impact, 500 micro Ci of K42 was injected and at 6 seconds after injection cardiac arrest was produced. And radioactivity of white matter was measured. The K42 uptake of the T6 white matter was 171%(SD=24) to that of T2, which was thought as a reflextion of increases regional blood flow. Alteration of blood-brain barrier resistance must be influenced upon the K+ ion uptake but they may be masked by increased blood flow, which was supported by a biphasic curve obtained from time-lag experiments, ie; decreased uptake in 1 1/2 hour group, increased uptake in 2 1/2 hour group and approach to the base line in the 4 hour group. Another experimental study to discover so called immediate physiological changes will be presented in the next report.