Surgical Management of Central Neuropathic Pain Using the Neuroablative Procedures of Brain

Central pain is defined as pain initiated or caused by a primary lesion or dysfunction within the central nervous system and has proved the most difficult pain to control. Many intracranial ablative procedures have been tried, including stereotactic cingulotomy, thalamotomy, and mesencephalotomy, which have been described to be effective in about 50% to 60% although the relief of pain is faded out with time. Anterior cingulotomy is effective for the relief of cancer pain and noncancer chronic pain. Although few side effects are potential benefits of cingulotomy, the effectiveness for central pain is not yet established. Mesencephalotomy is particular value in central denervation pain, cancer pain involving the head, neck but its use is limited due to significant morbidity. The value of thalamotomy for treatment of central pain is not documented. Trigeminal tractotomy and nucleotomy are beneficial for vagoglossopharyngeal neuralgia, geniculate neuralgia, and the caudalis DREZ is beneficial for atypical facial pain, postherpetic neuralgia. Recently neurostimulation is recommended for the treatment of central pain or neuropahic pain rather than neuroablation. The use of destructive central procedures for central pain and noncancer chronic pain has not yet been well defined. With the potential benefit being less certain, priority might be given to a procedure with less risk.ope

Characteristics and Pathways of the Somatosensory Evoked Field Potentials in the Rat

Objective：Somatosensory evoked potentials(SSEPs) have been used widely both experimentally and clinically to monitor the function of central nervous system and peripheral nervous system. Studies of SSEPs have reported the various recording techniques and patterns of SSEP. The previous SSEP studies used scalp recording electrodes, showed mean vector potentials which included relatively constant brainstem potentials(far-field potentials) and unstable thalamocortical pathway potentials(near-field potentials). Even in invasive SSEP recording methods, thalamocortical potentials were variable according to the kinds, depths, and distance of two electrodes. So they were regarded improper method for monitoring of upper level of brainstem. The present study was conducted to investigate the characteristics of somatosensory evoked field potentials(SSEFPs) of the cerebral cortex that evoked by hindlimb stimulation using ball electrode and the pathways of SSEFP by recording the potentials simultaneously in the cortex, VPL nucleus of thalamus, and nucleus gracilis. Methods：In the first experiment, a specially designed recording electrode was inserted into the cerebral cortex perpendicular to the cortical surface in order to recording the constant cortical field potentials and SSEFPs mapped from different areas of somatosensory cortex were analyzed. In the second experiment, SSEPs were recorded in the ipsilateral nucleus gracilis, the contralateral ventroposterolateral thalamic nucleus(VPL), and the cerebral cortex along the conduction pathway of somatosensory information. Results：In the first experiment, we could constantly obtain the SSEFPs in cerebral cortex following the transcutaneous electrical stimulation of the hind limb, and it revealed that the first large positive and following negative waves were largest at the 2mm posterior and 2mm lateral to the bregma in the contralateral somatosensory cortex. The second experiment showed that the SSEPs were conducted by way of posterior column somatosensory pathway and thalamocortical pathway and that specific patterns of the SSEPs were recorded from the nucleus gracilis, VPL, and cerebral cortex. Conclusion：The specially designed recording electrode was found to be very useful in recording the localized SSEFPs and the transcutaneous electrical stimulation using ball electrode was effective in evoking SSEPs. The characteristic shapes, latencies, and conduction velocities of each potentials are expected to be used the fundamental data for the future study of brain functions, including the hydrocephalus model, middle cerebral artery ischemia model, and so forth.ope

Microelectrode Recording-Guided Deep Brain Stimulation in Patients with Movement Disorders

Objective：The authors analyzed the findings of microelectrode recording data and reported the surgical outcomes of movement disorder patients. Methods：Since February 2000, the authors have used DBS for the movement disorders. We evaluated 4 patients who were followed more than 12 months after operation. One patient with essential tremor was treated with thalamic stimulation and three patients with idiopathic advanced Parkinson´s disease with bilateral subthalamic nucleus stimulation. The electrodes were inserted under microelectrode recording. Clinical assessments were performed preoperatively and postoperatively by neurologist. Results：All features of parkinsonian symptoms improved and the greatest benefit occurred in off-time and ADL. Interestingly our three patients with advanced Parkinson´s disease did not have off-time after bilateral stimulation of subthalamic nucleus. There were no adverse side effects related to microelectrode recording or DBS procedure in all 4 patients. In our results of microelectrode recording of subthalamic nucleus, subthalamus showed higher firing rate than that of substantia nigra pars reticularis. Mean burst frequency of subthalamic nucleus was much higher than that of substantia nigra pars reticularis. Conclusion：The first trials of DBS in Korea also demonstrated favorable outcomes for movement disorders.ope

Gamma Knife Radiosurgery for Craniopharyngioma

Objective：The purpose of this study are to evaluate the effectiveness of Gamma Knife radiosurgery(GKS) as a treatment of craniopharyngioma and to investigate the proper dose planning technique in GKS for craniopharyngioma. Method：Between May 1992 and March 1999, seven Gamma Knife radiosurgical procedures were done for residual tumor mass of 6 patients with craniopharyngioma after microsurgical resection. Conventional radiation therapy was not performed. In this study, their clinical, radiological and radiosurgical data were analyzed and the radiation dosage to the optic pathway, hypothalamus, pituitary stalk, and cavernous sinus were calculated and correlation with clinical outcome was evaluated. The mean follow-up period was 33.5 months(12.3-55.2 months). Result：The mean tumor volume was 4.4cc(0.4-18.0cc) and the maximum radiation dose ranged from 14 to 32 Gy(mean 20.9Gy). The radiation was given with isodose curve, 50-90% and the marginal dose varied within 8-22.4Gy(mean 12.7Gy). The mean number of isocenter was 4.3(1-12). The tumor was well controlled in all cases. In 5 of 7 cases, the size of tumor decreased to 10-50% of pre-GKS volume and remaining two showed no volume change. The mean dose to optic pathway was 5.7Gy(5.1-11.2Gy) and there were no complications. Conclusion：GKS seems to be effective for control of craniopharyngioma as an adjuvant treatment after microsurgical resection and even suboptimal dose for tumor margin is considered to be enough for tumor control. It is safe with careful dose planning to protect surrounding important structures, especially optic pathway. We believe conventional radiation therapy should be avoided because it has limitation for dose planning of additional treatments such as radiosurgery or intracystic instillation of radioisotope in case of recurrence.ope

Factors related to the success of Gamma Knife radiosurgery for arteriovenous malformations

Objective：The goal of this study was to evaluate the effect of Gamma Knife radiosurgery(GKS) on cerebral arteriovenous malformation(AVM) and the factors associated with complete occlusion. Patients and Methods：A total of 369 radiosurgical procedures for 336 patients with cerebral AVMs were performed between December 1988 and June 2001. Three hundreds and twenty-four cases of 293 patients who were treated with GKS procedures from May 1992 to December 2000 were analyzed. Various clinical and radiologic parameters were evaluated. Results：The total obliteration rate for the cases with satisfactory radiological follow-up(more than 2 years) after GKS was 79.3%. In multivariate analysis, maximal diameter, angiographic form of AVM nidus, and number of draining veins significantly influenced the result of radiosurgery. In addition, marginal radiation dose, Spetzler-Martin grade, and flow pattern of AVM nidi also partly influenced the radiosurgical outcome. Conclusion：GKS on cerebral AVM is considered as an effective treatment modality. The risk of hemorrhage seems to decrease within the latency interval between GKS and complete occlusion of nidus. Along with the size, topography, or radiosurgical parameters of AVMs, it is necessary to consider the angioarchitectural and hemodynamic aspects to select proper candidates for radiosurgery.ope

Treatment of intractable cancer pain by stereotactic bilateral anterior cingulotomy)

Objective：Although cingulotomy has been applied to patients with affective disorders more frequently, there are numerous reports of its use for the control of severe pain. The goal of this study was to investigate the role of stereotactic bilateral anterior cingulotomy for intractable cancer pain. Method：Between January and June, 2000, we underwent stereotactic bilateral anterior cingulotomy in 6 patients for intractable cancer pain with poor response to opioids. The patients were suffering from widespread musculoskeletal or visceral pain. We made four lesions along the two tracks on either side of the cingulate cortex. Result：In all patients, pain reliefs after cingulotomy were dramatic and immediate. Five out of six patients did not require any opioids and one patient could reduce dose of opioids. There were no deaths or serious complications related to the procedure. Conclusion：These results suggested that a bilateral anterior cingulotomy might be useful method to control intractable cancer pain associated with the widespread metastatic disease. To provide rationale of bilateral anterior cingulotomy in intractable cancer pain, the theoretical mechanisms and role of bilateral anterior cingulotomy are discussed, along with our surgical techniques and the course of our patients.ope

Functional Neurosurgery for Psychiatric Disease

Despite a long and controversial history, psychosurgery has persisted as a modern treatment option for some severe, medically intractable psychiatric disorders. The empirical basis of psychosurgery is weak because of the lack of well-designed investigations. Several carefully conducted studies in which independent evaluation has been made, however, show convincingly that highly selective stereotactic operations on the brain can benefit some carefully selected, chronically ill psychiatric patients with a low rate of unwanted side effects. The goal of this article is to review the current state of psychosurgery. In this review, the definition of psychosurgery, patient selection criteria, and anatomical and physiological rationales for anterior cingulotomy, subcaudate tractotomy, anterior capsulotomy, limbic leukotomy, vagus nerve stimulation and deep brain stimulation are discussed.ope

The Role of Postoperative Magnetic Resonance Imaging of Microvascular Decompression of the Facial Nerve in Patients with Hemifacial Spasm

Objectives：The objective of this study was to investigate the role of postoperative three dimensional short-range magnetic resonance angiography(3D-TOF MRA) in predicting the clinical outcomes following microvascular decompression(MVD) for the treatment of a hemifacial spasm(HFS). Material and Method：Postoperative magnetic resonance(MR) imaging was performed on 123 patients with a HFS between March 1999 and May 2000. All patients who had postoperative MR imaging were undertaken preoperative MR imaging. Of the 123 patients, 122 patients were included in this retrospective study. The degree of the detach-ment of vascular contact, and change of the position of offender were determined by pre- and postoperative 3D-TOF MRA. These findings were compared with the surgical findings and clinical outcomes. Results：Of 122 patients who had successful MVD, clear decompression of offenders of the root entry zone(REZ) of facial nerve was found in 106 patients(86.9%), partial decompression in 10 patients(8.2%) and contact of offenders to the REZ of facial nerve in 6 patients(4.9%) by the postoperative 3D-TOF MRA. Our patients demonstrated that the types of offender did not influence with the degree of decompression of REZ of facial nerve and with surgical outcomes(p>0.05). Also, there was no significant relationship between the degree of decompression of the REZ of facial nerve from offenders and an improvement of symptoms(p>0.05). Futhermore, there was no significant relationship between the degree of decompression of the REZ of facial nerve from offenders and an improvement time (p>0.05). Conclusion：Our data suggests that MVD of facial nerve alone may not be sufficient to resolve the symptoms in all patients with hemifacial spasm. Therefore, another unknown factors besides vascular compression may be involved to cause symptoms in certain patients and it may be necessary to remove these factors with MVD simultaneously to obtain the resolution of symptom.ope

Characteristics of Trigeminal Evoked Potentials in the Rat

Background: The trigeminal evoked potential (TEP) is one of the somatosensory evoked potenitals which have potential changes through the sensory pathway when the somatosensory nerve is stimulated. The present study was conducted to evaluate the characteristics of TEP through the trigeminal pathways. Methods: Under urethane anesthesia, male Sprague-Dawley rats were fixed to stereotaxic frame for evoked potential recording. The area around whiskers which is innervated by a pure sensory nerve branch of the trigeminal sensory pathway was stimulated and TEPs were recorded from the trigeminal nucleus, sensory thalamus, and somatosensory cortex. Results: Distinct TEP wave-forms were observed through the trigeminal pathways. The observed latencies were coincided with the ones expected through the conduction pathways of the trigeminal system. The latencies and amplitudes were specifically analyzed from different recording areas. Conclusions: The results suggest that relatively consistent TEPs can be recorded through the trigeminal pathway and these may afford normative data for the pathophysiological studies such as hydrocephalus, cerebral ischemia, and sensory disorders like trigeminal neuropathy.ope

(The) effect of halothane-induced hypotensive anesthesia on cerebral hemodynamics in dogs

의학과/박사[한글] [영문] An induced hypotension is employed as a useful technique for operations on intracranial aneurysms, brain tumors and other intracranial lesions to diminish operative bleeding and to decrease brain tension (Fazekas et al., 1956; McLaughlin, 1961). In aneurysm surgery under induced hypotension, the sac becomes softer and thus diminishes the risk of rupture when clips are applied (Hampton and Little, 1953: Hugosson and Hogstrom, 1973). In 1946 Gardner used arteriotomy to lower blood pressure by decreasing the blood volume during brain tumor surgery, then gradually improved. Pharmacologically-induced hypotension soon became the dominant method of producing hypotension. Halothane and trimethaphan are the most popular drugs for this purpose (Sarnoff et al., 1952: Murtagh 1960). On the other hand, the risks of hypotension are obvious. These include decreased cardiac output, decreased cerebral blood flow, and low perfusion pressure exposing brain tissue to the risk of hypoxia thereby aggravating the effects of the circulatory disturbance present in the brain lesion (Hampton and Little, 1953: Larson, 1964). In this situation the blood oxygen tension in jugular-bulb and lactate content in brain tissue have been found to be reliable indeces of degree of cerebral oxygenation (Viancos et al., 1966; Kaasik et al., 1970: Yashon et al., 1972). Consequently, several investigators have studied the critical level of arterial blood pressure during hypotensive anesthesia and have accepted 60 mmHg of systolic pressure (40-50 mmHg of mean arterial pressure) as a clinically applicable level free from the danger of cerebral hypoxia (Rollason and Hough, 1960; Eckenhoff et al., 1963). Furthermore, Griffiths and Gillies(1948) postulated that systolic pressure over 30 mmHg would provide adequate tissue oxygenation. However, there are only a few reports concerning the adequacy of cerebral oxygenation under such low levels of arterial blood pressure. The purpose of this study is to investigate ,cerebral hemodynamics and metabolism during halothane-induced hypotensive anesthesia and to find any evidence of cerebral hypoxia at the levels of 60 mmHg and 30 mmHg, of systolic blood pressure. 15 adult mongrel dogs, weighing 10-13 kg, were anesthetized with intravenous pentobarbital sodium. Endotracheal intubation was performed. One femoral artery was cannulated with a polyethylene tube for arterial blood sampling. The tube was connected to a Statham pressure transducer for continuous arterial blood pressure recording. The common carotid artery was exposed and a probe of square-wave electromagnetic flowmeter was placed on the vessel to record the carotid blood flow. An electrocardiogram and above two parameters were recorded simultaneously on a 4-channel polygraph. The internal jugular vein was cannulated and a catheter threaded up to the jugular-bulb for sampling of venous blood draining from the brain. The cisterna magna was punctured with an 18 gauge spinal needle to sample the cerebrospinal fluid. The experiments were divided into control phase, induction phase, hypotensive phase Ⅰ, hypotensive phase Ⅱ, and recovery phase. Each chase was maintained for 30 minutes. Cerebrospinal fluid, arterial and venous blood were sampled at the end of each phase for analysis of gas tension and lactate content. 100% oxygen was inhaled during the induction phase. During the hypotensive phases, halothane/O^^2 was administered to lower the arterial blood pressure. In the hypotensive phase I and hypotensive phase Ⅱ systolic pressure was maintained at 60 mmHg and 30 mmHg, respectively. In the recovery phase, halothane was discontinued and 100% oxygen only was inhaled. The results obtained are summarized as fellows: 1. The carotid artery blood flow, which represents the cerebral blood flow, decreased linearly during the decline of the arterial blood pressure. At the end of each phase there was no-difference in the carotid blood flow between hypotensive phase Ⅰ and Phase Ⅱ. Cerebral vascular resistance was markedly reduced in the hypotensive phase Ⅱ, which suggests cerebral vasodilatation. 2. Cerebral venous pO^^2 decreased significantly in the hypotensive phases, but the values still remained within normal limits. A marked reduction of arterial pCO^^2 was noted in the hypotensive phases. The values approach the lower limits of safety. 3. The most outstanding difference between hypotensive phase Ⅰ and phase Ⅱ is in the lactate content of cerebral venous blood and cerebrospinal fluid. There was a moderate increase of lactate content, and a slight reduction of cerebral venous pH in hypotensive phase Ⅱ, however, a significant degree of cerebral hypoxia and metabolic acidosis could be excluded. 4. Most of the changes in the cerebral metabolism and hemodynamics including arterial blood pressure, tend to return to normal at the end of the recovery phase. From the result of this study, it is concluded: 1. Halothane-induced hypotensive anesthesia at 60 mmHg of systolic blood pressure (45 mmHg of mean arterial pressure) is a safe level without threat of cerebral hypoxia. 2. Although there is some possibility of a mild metabolic acidosis at 30 mmHg of systolic blood pressure (23 mmHg of mean arterial pressure), adequate cerebral oxygenation is maintained without difficulty.restrictio