Posteroventral medial pallidotomy for treatment of Parkinson's disease: preoperative magnetic resonance imaging features and clinical outcome

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Abstract
Object. The goal of this study was to investigate the impact of mild or moderate degrees of degenerative or ischemic encephalopathy on predicting clinical outcome following unilateral posteroventral medial pallidotomy for treatment of advanced Parkinson's disease (PD). Methods. Thirty-five patients with PD were studied prospectively. The presence and degree of cortical atrophy, ventriculomegaly, deep white matter lesions (DWML), periventricular lucencies (PVL), and the presence of lacunes and status cribriformis (multiple and bilateral enlarged Virchow—Robin spaces) were determined by magnetic resonance (MR) imaging before the patients underwent stereotactic pallidotomy performed according to a standard protocol. Clinical outcome was measured using a standard battery of tests including application of the Unified Parkinson's Disease Rating Scale (UPDRS). The preoperative MR imaging features were correlated with UPDRS subscores such as motor “off” score, the activities of daily living (ADL) off score, the off subscore for bradykinesia, the percentage of “on” time dyskinesias, and a global outcome rating. The MR findings were also correlated with the occurrence of side effects. Global outcome was rated as markedly improved in 22 patients (63%) and as moderately improved in 12 patients (34%) 6 months postoperatively. At the 1-year follow-up examination, global outcome in 31 patients was rated as markedly improved in 14 patients (45%), as moderately improved in another 14 (45%), as slightly improved in two (6%), and as worse in one patient (3%). The mean UPDRS motor off score changed from 58.7 preoperatively to 33.2 at 6 months and 33.4 at 1 year (p < 0.0001), the ADL off score from 31.8 to 18.2 at 6 months and 18.6 at 1 year (p < 0.0001), the off score from contralateral bradykinesia from 11.6 to 5.6 at 6 months and 4.1 at 1 year (p < 0.0001), and the percentage of awake time with dyskinesias from 37.4 to 17.4% at 6 months and 21.1% at 1 year (p < 0.0001). The presence of mild or moderate degrees of cortical atrophy, PVL, and DWML had no effect on clinical outcome. Patients with status cribriformis and those with lacunes tended to show comparatively less improvement in the UPDRS ADL off score (p = 0.014 and p = 0.016, respectively) at 6 months. This tendency was also present in patients with status cribriformis 1 year postoperatively (p = 0.046). Patients with both status cribriformis and lacunes had a higher incidence of transient altered mental status immediately postoperatively (p = 0.05). Conclusions. Mild-to-moderate degrees of cortical atrophy, ventriculomegaly, and ischemic encephalopathy do not predispose patients to less favorable outcomes following unilateral pallidotomy. Patients with both status cribriformis and lacunes have a higher risk of transient side effects; however, with regard to clinical outcome, these patients should not be denied surgical treatment.