Bilateral subthalamic or pallidal stimulation for Parkinson's disease affects neither memory nor executive functions: A consecutive series of 62 patients

Abstract

There is a renewal of interest in surgical approaches including lesions and deep brain stimulation directed at motor subcorticofrontal loops. Bilateral lesioning presents a far greater risk of adverse effects, especially cognitive impairment. Furthermore, the main advantages of the stimulation procedure over lesioning are adaptability and reversibility of effects. The aim of this study was to assess the influence of bilateral stimulation of the subthalamic nucleus or internal globus pallidus on memory and executive functions in Parkinson's disease. Sixty‐two patients were assessed before and after 3 to 6 months of chronic bilateral stimulation of the subthalamic nucleus (n = 49) or internal globus pallidus (n = 13). The neuropsychological tests used were the Mattis Dementia Rating Scale, the Grober and Buschke Verbal Learning Test, the Wisconsin Card Sorting Test, category and literal fluency, graphic and motor series, the Stroop Test, and the Trail Making Test. Mood was evaluated by the Beck Depression Inventory. Only 4 of 25 cognitive variables were affected by deep brain stimulation. Under stimulation, performance improved for Parts A and B of the Trail Making Test, but there was a deterioration in literal and total lexical fluency. There was also a mild but significant improvement in mood. It may therefore be concluded that stimulation of the subthalamic nucleus or internal globus pallidus does not change the overall cognitive performance in Parkinson's disease and does not greatly affect the functioning of subcorticofrontal loops involved in cognition in humans. This relative absence of cognitive impairment in bilateral deep brain stimulation is likely because of the accurate positioning of the electrodes, allowing the effects of stimulation to be confined to sensorimotor circuits. Ann Neurol 1999;46:217–223

Effects of Deep Brain Stimulation on Cognition, Mood and Behaviour in Parkinson’s Disease

“…[30][31][32][33][34] These studies, with few exceptions, 20,[35][36][37][38][39] have observed small and circumscribed cognitive changes, most often in verbal fluency (timed oral word generation according to different phonemic or semantic constraints). 16,17,37,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] Even among studies reporting more widespread cognitive declines there is disagreement as to the clinical meaningfulness of these changes. Alegret and co-workers 35 interpreted the changes not to be of clinical significance, in contrast to Saint-Cyr et al 38 and Smeding et al 39 As many of the neuropsychological studies of STN DBS have small sample sizes, greater weight should be given to the five controlled neuropsychological studies (excluding studies limited to language or cognitive screening evaluations), even though each has significant methodological and/or conceptual limitations.…”

“…[16][17][18] Nonetheless, a small minority of patients may develop cognitive morbidity. One case with magnetic resonance imaging (MRI)-confirmed electrode location had significant executive dysfunction ensuing from bilateral GPi DBS; importantly, when the stimulators were turned off, the impairment was partially reversed, thereby suggesting a direct role of stimulation in the neuropsychological deficit.…”

“…Several studies using patient-report inventories have reported improvement in depressive symptomatology. 16,38,74,75 Similarly, studies disagree as to whether apathy does or does not increase after STN DBS. 55,76 On the one hand, studies reporting post-operative incidence of behavioural changes typically do not report a change from the pre-operative state, leaving it possible that the incidence of psychiatric conditions actually improves from pre-operative levels.…”

Long-term outcome of subthalamic nucleus DBS in Parkinson's disease: From the advanced phase towards the late stage of the disease?

“…The neuropsychological assessment confirmed a worsening of phonological verbal fluency after STN-DBS, as already described in the short-term [17].…”

Apathy in Parkinson's disease: clinical features, neural substrates, diagnosis, and treatment

“…110 Long-term, treatment-resistant postoperative apathy tends to develop in association with levodopa-resistant frontal dysexecutive syndrome, and can be explained by diff use cortical synucleinopathy 2,10,50,56,111,112 rather than by STN-DBS on its own. Although dementia might be a part of Parkinson's disease progression, 113,114 in the young and largely cognitively preserved populations of patients with Parkinson's disease who are generally selected for deep brain stimulation, overall cognition, including frontal dysexecutive syndrome, is relatively stable 115,116 in the fi rst years after STN-DBS, although in a small proportion of patients, surgery itself can induce cognitive deterioration. 117 Surgical treatment of Parkinson's disease has given rise to a new phenotype of patients with advanced Parkinson's disease who have little akinesia, no tremor or rigidity, and little dyskinesia, and are mainly disabled by frontal dementia, apathy, and levodoparesistant axial motor features.…”