Neuropsychological consequences of pallidal lesions and subthalamic stimulation for the treatment of Parkinsonian patients

by Trepanier, Lisa Laura

Abstract (Summary)
Patients with advanced idiopathic Parkinson's disease (PD) have motor. cognitive and affective impairrnents due to the progressive dopamine deficiency which disrupt the functional integrity of frontal-striata1circuitry. Recent functional neurosurgical treatment strategies, aimed at neural targets within this circuitry, can further influence these processes. The main purpose of this dissertation was to examine the impact of two neurosurgical treatments, unilateral posteroventral pallidotomy (U-PVP) (n=42; 18L and 24R) and bilateral deep brain stimulation of the subthalamic nucleus (STN-DBS) (n=l 1 ; 6 > 69; 5 < 69 years old) on neuropsychological functioning in patients with advanced idiopathic PD. In Study 1, it was found that patients with U-PVP can experience clinical motor benefits and improvements in allocation of attentional resources but can also suffer declines in working rnemory and in certain aspects of frontal executive functioning. There were lateralized declines in verbal learning and fluency following left-sided lesions and visuownstnictional abilities following right-sided lesions. Only declines in verbal leaming and fluency were chronic. Lastly, behavioural changes of a "frontal naturen, which could increase dependence and negatively affect relationships, were reported in 2530% of patients. In Study 2, it was found that patients with bilateral STN DBS cm experience clinical motor benefits at 3-6 months but many aspects of cognitive functioning decline. These were noted in working memory, speed of mental processing, bimanual motor speed and CO-ordination, set switching, phonemic fluency, long-term consolidation of verbal material and the encoding of visuospatial material. "Frontal" behavioural dyscontrol, without the benefit of insight, was also reported in the elderly subgroup. Except for learning tasks based on multiple trials, tasks reliant on the integrity of frontal-striatal circuitry either did not recover or gradually worsened over time, especially in patients > 69 years old. Conclusion: Both treatments can have a negative impact on patients! neuropsychological functioning. Elderly patients are especially vulnerable and bilateral STN DBS can impair cognition more severely than U-PVP. These findings are consistent with the explanation that lesions or chronic stimulation of neural targets within frontal-striatal circuits can cause further deterioration of processes normally thought to be dependent on their functional integrity. Kev Words: Neuropsychoiogy, Basal Ganglia, Neurosurgery. Pallidotomy, Deep Brain Stimulation, Parkinson's Disease. Acknowledciements I gratefully acknowledge the expert guidance. support, and encouragement that I received from my supervisor, Dr. Jean Saint-Cyr, throughout this extensive research endeavour. Thank you for giving me such an incredible learning experience throughout ail of my graduate training. My appreciation is extended to my other cornmittee members, Drs. Harvey Brooker. Neil Wiener. Jeanne Ridgley, Joe Levy, and Anne-Marie Wall, for their helpful comrnents and involvernent in the completion of my dissertation. I would also like to extend my sincere gratitude to Drs. Lang, Lozano, Kumar. Davis, and Hutchison, for giving me the opportunity to participate on a multidisciplinary team carrying out such tremendous research in movernent disorders. You are all a source of inspiration for me. In this regard, a special thank you goes to Dr. Lang for his support of me through one of the "rough spots " . Lastly. 1 would like to thank my family and friends for their love, support, and belief in me throughout my joumey. i dedicate this work to my darling son, Cameron. vii
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Source Type:Master's Thesis



Date of Publication:01/01/2000

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