Microelectrode-guided posteroventral pallidotomy for treatment of Parkinson's disease: postoperative magnetic resonance imaging analysis

Abstract

The authors report the postoperative magnetic resonance (MR) imaging findings in 36 patients with advanced Parkinson's disease who underwent unilateral microelectrode-guided posteroventral pallidotomy. The lesions were placed within 1 mm of the ventral border of the globus pallidus internus (GPi) to include pallidothalamic outflow pathways. Sequential MR studies were obtained within 1 to 3 days postoperatively and at 6-month follow-up examination. Thirty-four (94%) of the 36 patients enjoyed sustained moderate or marked improvement of their parkinsonian symptoms 6 months postoperatively. Transient side effects occurred in five patients (14%), but there were no persistent complications. The pallidal radiofrequency lesions were prolate spheroid-shaped and were composed of three concentric zones in the early postoperative studies. The mean volume of the middle zone, corresponding to the area of hemorrhagic coagulation necrosis, was 44.4 +/- 17.6 mm3; the mean lesion volume as defined by the outer zone, corresponding to perilesional edema, was 262.2 +/− 111.6 mm3. Additional edema spreading to the internal capsule was noted in 32 of 34 cases and to the optic tract in 11 of 34 cases. In two patients small ischemic infarctions involving the corona radiata were found, and in one a venous infarction was detected. Ischemic infarction resulted in mild transient Broca's aphasia in one patient, but there was no detectable neurological deficit in the other two. The mean volume of late-phase (6 months) lesions was 22 +/− 28.8 mm3. In three patients no lesion was identified despite sustained clinical improvement. The lesion was located in the posteroventral GPi in all cases except in one patient in whom it was confined to the GP externus (GPe). This 49-year-old woman did not experience sustained benefit. The authors found no consistent correlations between lesion size and location and clinical outcome as measured by a global outcome score, the Unified Parkinson's Disease Rating Scale motor, activities of daily living, and bradykinesia “off” scores or rating of dyskinesias. Lesioning of pallidal and subpallidal pathways may contribute to the sustained clinical benefit in this series. Magnetic resonance imaging analysis showed that intraoperative microelectrode recording facilitated accurate placement of the lesion in this critical area.

Unilateral subthalamic nucleus lesioning: a safe and effective treatment for Parkinson's disease

“…Krauss et al 34 reported a somewhat similar result in patients who underwent medial pallidotomy. The acute-phase aspect on T2-weighted MRI images was of a three-concentric-zone lesion: a hyperintense inner zone, a hypointense middle zone (thought to represent hemorrhagic coagulation necrosis) and a hyperintense outer zone (thought to correspond to edema), involved by additional perilesional edema, with a signal not as intense as the lesion outer zone; the late-phase aspect was of a hyperintense lesion.…”

“…The MRI aspect of a radiofrequency lesion was first described by Tomlinson et al, cited by Krauss et al 34 , in patients submitted to ventrolateral thalamotomy. Krauss et al 34 reported a somewhat similar result in patients who underwent medial pallidotomy.…”

“…Likewise, Krauss et al 34 performed late MRI (usually six months after the operation) in 32 out of 36 patients who underwent medial pallidotomy; no lesion could be observed in three of them. Using a method first described by our group, we were able to determine the STN territory involved by the lesion.…”

“…With regard to the two-and three-concentric-zone lesions, the outer zone, considered by some as a mere edema 34 , was not included in the measurement.…”

Pathophysiology of Drug-Induced Dyskinesias

“…The anti-dyskinetic effect of pallidotomy is considered the function of normalizing the pattern of firing of GPI (Guridi et al, 2008). The optimal lesion location within the GPI has been variously argued to be anteromedial (Gross et al, 1999) and posteroventral (Krauss et al, 1997).…”