Magnetic Resonance Image Guided Unilateral Pallidotomy for Parkinson's Disease; Surgical Technique and Clinical Efficacy

OBJECTIVE: The authors present a clinical analysis to determine the clinical efficacy of unilateral palliotomy for Parkinson's disease without microelectrode recording procedure and to review the surgical technique, based on the anatomical landmark using magnetic resonance(MR) image. METHODS: Twenty-seven patients were retrospectively studied with extensive neurological examinations including Unified Parkinson's Disease Rating Scale(UPDRS) in 'levodopa-on and -off' tate before and at 6 and 12 months following MRI-guided pallidotomy. Lesion location was characterized using thin sliced MR image and measured on axial slice of TOF image. Lesion was performed with radiofrequency lesion generator. RESULTS: Final surgical target was 2.7+/-0.3mm in front of the intercommissural point, 4.0+/-1mm below the imtercommissural line, and 20.2+/-1.4mm lateral to the midline of the third ventricle. Significant improvements were observed in the total UPDRS scores and motor scores. And there was no significant postoperative complication and sequale except transient paresis(2 cases) and dysarthria(1 case). CONCLUSION: Steretotactic MR image guided pallidotomy with macrostimulation for the patients with Parkinson's disease is safe with minimal morbidity and significantly reduces the disabilities of Parkinson's disease.

Pallidotomy Guided by MRI and Microrecording for Parkinson's Disease

OBJECTIVE: The exact position of the lesion during the pallidotomy is critical to obtain the clinical improvement of parkinson's disease without damage to surrounding structure. Ventriculogrphy, CT(computed tomograpy) or MRI(magnetic resonance imaging) have been used to determine the initial coordinates of stereotactic target for pallidotomy. The goal of this study was to determine whether microelectrode recording significantly improves the neurophysiologic localization of the target obtained from MRI. METHODS: Twenty patients were studied. They underwent a unilateral pallidotomy. Leksell frame was applied and T1 axial images parallel to the AC-PC(anterior commissure-posterior commissure) plane using a 1.5 Tesla MRI with 3mm slice thickness were obtained. Anteroposterior coordinate of target was chosen at 2mm in front of the midcommissural point and lateral coordinate between 19 and 22mm from the midline. The vertical coordinate was calculated on coronal slice using a fast spin echo inversion recovery sequence(FSEIR) related to the position of the choroidal fissure and ranged over 4-5mm below the AC-PC plane. Confirmation of the anatomical target was done on axial slices using the same FSEIR sequence. Microrecording was done at the pallidum contralateral to the symptomatic side using an electrode with a tip diameter of 1nm diameter tip and 1.1-1.4 mOhm impedance at 1000Hz. Electrophysiologic localization of the target was also confirmed intraoperatively by macrostimulation. RESULTS: Microrecording techniques were reliable to define the transition from the base of the pallidum which was characterized by the disappearance of spike activity and by the change of the audible background activity. Signals from high amplitude neurons firing at 200-400Hz were recorded in the pallidal base. X, Y and Z coordinates of target obtained from the MRI were within 1mm from the X, Y, Z coordinates obtained with microrecording in 16 patients (80%), 15 patients(75%), 10 patients(50%) respectively. The difference of Y coordinate between on MRI and on microrecording was 4mm in only one patient. CONCLUSION: The MRI was accurate to localize the target within 1mm of the error from microrecording target in 70% of the patients. 4mm discrepancy was observed only once. We conclude that MRI alone can be used to determine the target for pallidotomy in most patients. However, microrecording technique can still be extremely valuable in patents with aberrant anatomy or unusual MRI coordinates. We also consider physiologic confirmation of the target using macrostimulation to be mandatory in all cases.