Radiofrequency thermocoagulation과 Radiofrequency coagulation이 개의 중추신경조직에 일으키는 반응에 관한 연구
(A) comparative histological study of radiofrequency thermocoagulation and coagulation in central nervous system of dog
정위수술시 신경조직을 파괴하는 방법으로 과거에는 직접적인 조직의 절제 또는 분쇄(Clarke, 1920; Bertraud et al, 1966), 알콜등을 이용한 화학적 파괴(Cooper 및 Bravo 1958; Mc Caul, 1959), 냉각법(Cooper, 1962; Wannestrand 등 1967), 엑스선 조사(Bagg, 192
1; Edwads 및 Bagg, 1923) 및 초음파(Barnard등, 1956; Fry. 1958) 등이 사용되어 왔으나 이상의 방법들은 정위수술시 요구되는 표적에 대한 일정한 크기의 병소를 만들어야 되고 수술조작이 간단해야 한다는 조건들을 만족시킬 수가 없었다. Aronow(1960)가 단파병소
유발기 (radiofrequency lesion generator)를 제작한 이후 단파를 이용한 정위수술법이 본격화 되어 현재 신경외과 분야에서 널리 사용되고 있다.
단파응고(radiofrequency coagulation) 때에는 0.2 MHZ로부터 4MHZ의 전류를 신경조직에 통과시킬 때 활성전극을 신경조직내에 두고 불관전극을 원격근육 조직내에 두면 활성전극 주위신경조직이 갖는 전류에 대한 저항 때문에 열이 발생하여 신경조직의 단백질이
응고된다(Van Buren 및 Ratcheson, 1973) 한편 단파열응고(radio-frequency thermocoagulation)는 전극에 전류가 통과할 때 전극 자체가 가열되어서 전극 주위의 신경조직이 응고된다(Carpenter 및 whittier, 1952; Dieckmann. 1965)
저자는 단파열응고 및 단파응고시에 형성되는 병소가 시간에 따른 신경 조직의 형태학적 변화와 크기 및 건강신경 조직과의 경계등을 조사함으로써 정위수술시 보다 신빙성이 있는 병소를 만드는데 참고하고자 9마리의 개에서 대뇌 회백질과 척수 회백질에 각기 단파열 응고와 단파응고를 실시하고 병소유발 직후부터 2주까지 발생하는 각병소의 크기 모양 및 조직학적인 반응을 광학현미경과 전자현미경으로 관찰하고 다음과 같은 성적을 얻었다.
1. 단파응고시에 전극의 끝이 2mm 노출되게 하고 15초간 병소를 만들었을 때에 병소의 크기가 50mA에서는 (1.4±0.14) x (4.0±0.26)mm, 80mA에서는 (1.8±0.19) x (4.8±0.16)mm, 그리고 110mA에서는 (2.1±0.17) x (4.9±0.23)mm로서 80mA이상에서는 병소의 크기가 더 이상 현저히 증가하지 않았다.
2. 단파열응고시 전극의 끝이 5mm 노출되게 하고 2분간씩 병소를 만들었을 때에 병소의 크기는 60。C에서 (5.3±0.14) x (7.5±0.14)mm, 70。C에서 (7.0±0.4) x (9.7±0.14)mm, 그리고 80。C에서는 (8.6±0.16) x (11.6±0.26)mm이었다.
3. 일차병소를 만든 후 동일한 장소에서 이차병조를 만들었을 때에 그 병소의 일차병소 보다 1mm이하로 증가 하였다.
4. 일반적으로 병소의 경계는 양군에서 일정하지 않았다.
5. 광학현미경적 관찰에서는 양군에서 병소유발직후 및 24시간 후에는 병소에 괴사, 변성, 출혈, 부종, 섬유양물질 및 삼출등이 관찰되었으며, 1주후와 2주후에는 60cm세포의 출현과 육아조직이 형성되었는데 양군에서 특이한 차이는 없었다.
6. 척수 회백질에서는 대뇌 회백질에 비해 광학 현미경적 및 전자현미경적 변화가 더욱 현저하고 빨랐다.
7. 양실험군에서 신경세포의 미세구조중 사립체의 변화가 관찰되었으며, 시간이 경과함에 따라 비정상적인 신경세포를 볼 수 있었다. 그리고 접합부위는 비교적 오랫동안 유지됨을 관찰할 수 있었다.
8. 척수 회백질의 신경섬유는 부분적으로 파괴되었다.
9. 동물의 미세한 호흡운동이 병소의 크기 및 경계에 현저하고 영향을 미치는 것으로 사료된다.
A method for destroying discrete, circumscribed areas of nervous system in constant fashion is a prerequisite for stereotaxic surgery. Many methods including mechanical cutting or crushing(Clarke, 1920; Bertrand et al., 1966), chemical destruction(Cooper, 1958; McCaul, 1957), cooling (Cooper, 1962; Wannenstrand, 1967), radiation (Bagg, 1921; Edwards, 1923) and ultrasound (Barnard et al., 1956; Fry, 1958) have been used but each of above methods have some shortness to fulfill the prerequisite for stereotaxic surgery completely.
Saul Aronow devised a radiofrequency lesion generator in 1960, which could make a discrete, predicted lesion in human nervous tissue. And recently this method is widely employed in neurosurgery (Van Buren, 1965). Radiofrequency coagulation of
tissue satisfactory for stereotaxic lesions occurs when the current passed is between frequencies of 0.2 MHz and 4 MHz over a wide range of current values(Alberts et al., 1966). Most commonly a radiofrequency of 2 MHz is employed. While the dimensions of the lesion are related to the power input, specifically temperature obtained, the current, and the duration of current, and other specific characteristics such as the geometry of the electrode and the character of the tissue are also operative in determining the final result (Van Buren, 1973)> In general, the size of the lesion may be more reliably adjusted by changing the
electrode than by substituting other parameters (Dieckmann, 1965). Within the range of frequencies just mentioned, only a miner portion of the tissue destruction is due to resistive heating of the electrode and is dependent of the frequency. The
major tissue destruction is the result of a frequency-dependent dielectric effect in the tissues when electric energy is converted into heat (Aronow, 1960; Petty and Edsall, 1967). The most important factors appear to be the density and the ohmic
resistency of the tissue (Alberts and Wright, 1966).
Cerebral lesions dependent upon heat for their production are influenced by the presence of blood vessels, the spatial relationship to the cerebrospinal fluid pathways, and the tissue resistivity (Dieckmann, 1965). The greater vascularity of the gray matter and its greater ability to dissipate heat will require more power than is needed to produce a lesion of equal size in the white matter(Aronow, 1960; Dieckmann, 1965; Van Buren, 1973).
The histologic examination of the lesions after radio-frequency coagulation in animal central nervous system was reported by Petty and Edsal (1967) and Sweet et al. (1960). Carpenter and Whittier (1952) inserted magnetic wires into subcortical structures in the experimental animal and the head was placed in an electromagnetic field generated by a high-frequency induction heating unit. Resultant lesions were of uniform size and shape with a circular configuration and were unaccompanied by a distant intracerebral injury. Dieckmann studied histologic changes of lesions following radio-frequency thermocoagulation in experimental animals (1965).
The present study is an attempt to evaluate histologic changes after radiofrequency thermcoagulation and radio-frequency coagulation in a mammalian cental nervous system and to compare them.
Materials and method.
Nine Korean adult dogs weighing an average of 10kg. were used in this experiment, each being anesthetized with intravenous injection of phenobarbital (30mg/kg), intubated and maintained under spontaneous respiration. Lesions were produced in the cerebral subcortex by radio-frequency thermocoagulation and coagulation and in the spinal cord by radio-frequency coagulation utilizing a radio-frequency lesion generator. (Radionics Model RFG-3AV).
The electrode for thermocoagulation had 5mm. of its terminal bare of insulation and a 2mm. bare electrode was used for radio-frequency coagulation. Thermocoagulation was done at from 60'c to 80'c for two minutes and radiofrequency coagulation at from 50mA to 110mA for 15 seconds. The animals were killed at intervals varying from immediately to two weeks after the lesion making to evalua histologic changes. The results obtained are summarized as follows:
1. The average size of lesions in the radiofrequency coagulation group with 2mm. bare electrode and 15 second maintenance of current at 50mA was 1.4 by 4.0mm., 1.8 by 4.8mm. at 80mA and 2.1 by 4.9mm. at 110mA.
2. The average size of lesions in radiofrequency thermocoagulation group with a 5mm. bare electrode and 2 minutes maintenance of temperature at 60'c was 5.3 by 7.5mm. 7.0 by 9.7mm. at 70'c and 8.6 by 11.6mm. at 80'c.
3. Repeated lesions in the same area as that of the primary lesion caused less than 1mm. increase in size. Thus it was suggested that an operator should make a repeated lesion in human central nervous tissue only after with-drawl or advance of electrode from a primary lesion site.
4. In both groups the majority of lesions had irregular margins.
5. Immediate histologic change of lesions in both groups were characterized by necrosis, degeneration, hemorrhage, and edema; chronic changed by appearance of foam cells in the central area of lesions and granulation tissue in the nearby area.
6. In the spinal cord the histologic changes were more rapid and complete than those in the brain.
7. In both groups prominent structural changes in mitochondria were disclosed were disclosed on electron microscopic examination and neuronal changes had progressed greatly within a day in contrast to the synaptic portion.
8. In the spinal cord radiofrequency coagulation caused greater destruction of myelin sheath than the axon.
9. In both groups size and margin of the lesions were greatly influenced by spontaneous respiration of the experimental animals. liver diseases, gastrointestinal diseases and other miscellaneous diseases, respectively.
The frequency of serologic test according to the clinical group revealed positive rates of 88.9, 72.0, 0.0, 4.4, 22.0 and 0.0 per cent by 3 tests(IHA, IFA and AI), 7.4, 24.0, 23.5, 12.5, 22.2and 9.1 per cent by 2 tests (IHA & IFA, or IHA & AI, or IFA & AI), 3.7, 0.0, 35.3, 37.5, 50.0 and 50.0 per cent by only 1 test (IHA or IFA or AI), and negative results of 0.0, 4.0, 41.2, 45.8, 5.6 and 40.9 per cent, in groups of extraintestinal amebiasis, intestinal amebiasis, miscellaneous liver diseases, miscellaneous gastrointestinal disease, other miscellaneous diseases and
apparently healthy controls, respectively.
The results indicated that 1) IHA, IFA and AI test positive serum would support the disease was amebic origin, 2) only 1 test positive or three tests negative serum might be clinically not significant, and 3) the two tests positive serum would need another stool examinations and clinical findings for reliable diagnosis.