Risk factors for executive dysfunction after subthalamic nucleus stimulation in Parkinson's disease

Review: management of Parkinson's disease

Parkinson's disease (PD) is one of the most frequent neurological diseases. Despite the modern imaging and nuclear techniques which help to diagnose it in a very early stage and lead to a better discrimination of similar diseases, PD has remained a clinical diagnosis. The increasing number of available treatment options makes the disease management often complicated even when the presence of PD seems undoubted. In addition, nonmotor symptoms and side effects of some therapies constitute some pitfalls already in the preclinical state or at the beginnings of the disease, especially with the progressive effect on patients. Therefore, this review aimed to summarize study results and depict recommended medical treatments for the most common motor and nonmotor symptoms in PD. Additionally, emerging new therapeutic options such as continuous pump therapies, eg, with apomorphine or parenteral levodopa, or the implantation of electrodes for deep brain stimulation were also considered.

Psychiatric side-effects of bilateral deep brain stimulation for movement disorders

INTRODUCTION

The effects of deep brain stimulation (DBS) on cognitive functions, and its psychiatric side-effects, are still controversial. The present study investigated psychiatric comorbidity and postoperative effects of DBS of different targets on mood and psychological functions in 81 patients with a mean follow-up of 37 months.

METHODS

A total of 109 patients underwent implantation of DBS electrodes between 2001 and 2006; it was possible to evaluate 81 patients by a psychiatric test battery using the "Neuropsychiatric Inventory". To evaluate the possible influence of the target, we analyzed the data without 16 patients with DBS surgery for other diseases (e.g., epilepsia, cluster headache) or unilateral implantation only. The resulting population (n = 65, mean age 61 years, range 23-78 years, male:female 42:23) consisted of 43 Parkinson's disease patients stimulated in the subthalamic nucleus, ten dystonia patients stimulated in the globus pallidus internus, and 12 tremor patients in the ventral intermediate nucleus.

RESULTS

There was a high rate of preoperative psychiatric comorbidity, which is reflected by a high rate of patients with preoperative medication of neuroleptic drugs (18.4 %, especially clozapin 14.7 %) and antidepressive drugs (16.5 %). Depression was the most common psychiatric side-effect after DBS, occurring in 47.7 % of all patients (31/65 patients), without significant preference to a specific target (STN: 42 %, Gpi: 60 %, VIM: 58 %). Delusion (n = 5 out of 43 PD patients, 11.6 %), euphoria (n = 1, 2.3 %) and disinhibition (n = 3, 7.0 %) were seen in the PD patients only.

CONCLUSION

A wide range of behavioural changes may be seen following DBS. Depression was the most common side-effect after DBS, and occurred independently of the target. PD patients, in contrast to dystonia and tremor patients, developed complications in all tested subgroups, with varying frequencies. Preoperative evaluation for psychiatric and cognitive dysfunction is crucial to identify patients who are at specific risk for psychiatric complications.

Clinical outcome of deep brain stimulation for Parkinson's disease

Deep brain stimulation is one of the most effective treatments of Parkinson's disease (PD). This report summarizes the state of the art as at January 2013. Stimulation of the subthalamic nucleus is the most commonly used approach. It improves the core motor symptoms better than medication in patients with advanced disease. It also improves the majority of nonmotor symptoms, such as mood, impulse control disorders, sleep, and some autonomic dysfunctions. Quality of life (QoL) is improved significantly more than with medication. Long-term data show that the treatment is effective for up to 10 years, but the late appearance of l-dopa-resistant symptoms is seemingly not influenced. Internal globus pallidus (GPi) stimulation is less well studied but seems to have similar short-term efficacy. Importantly l-dopa use cannot be reduced with GPi DBS, which is a major disadvantage for patients suffering from medication side-effects, although gait may be influenced more positively. Although short-term QoL improvement seems to be similar to that for subthalamic nucleus (STN) DBS - gait and speech may be better improved - long-term data are rare for GPi DBS. Thalamic stimulation in the ventral intermediate nucleus (VIM) is applied only in tremor-dominant elderly patients. The treatment improves the dopa-sensitive symptoms and effectively reduces fluctuations leading to an overall QoL improvement. Although most of the controlled studies have been on advanced PD, the recently published EARLYSTIM study suggests that even patients with a very short duration of their fluctuations and dyskinesia are doing significantly better with neurostimulation in terms of QoL and all major motor outcome parameters.

Cognitive impairment in patients with Parkinson's disease: diagnosis, biomarkers, and treatment

Dementia is one of the most common and important aspects of Parkinson's disease and has consequences for patients and caregivers, and has health-related costs. Mild cognitive impairment is also common and frequently progresses to dementia. The underlying mechanisms of dementia associated with Parkinson's disease are only partly known and no mechanism-based treatments are available. Both dysmetabolism of α-synuclein and amyloid-protein and cholinergic deficits contribute to cognitive impairment in Parkinson's disease, and preliminary findings show that imaging and neurophysiological and peripheral biomarkers could be useful in diagnosis and prognosis. Rivastigmine is the only licensed treatment for dementia in Parkinson's disease, but emerging evidence suggests that memantine might also be useful. Whether these or other treatments can delay the progression from mild cognitive impairment to dementia in Parkinson's disease is a key research question.

The pattern of attentional deficits in Parkinson's disease

BACKGROUND

Cognitive impairment without dementia is frequent in Parkinson's disease. It often presents as a dysexecutive syndrome with deficient attentional resource allocation. The nature of attention deficits in Parkinson's disease has rarely been investigated with robust, theory-based tasks. The main objective of the present study was to investigate attention disorders in Parkinson's disease patients by applying a paradigm based on a model of attention. We also sought to identify the main demographic and clinical characteristics associated with attention deficits in Parkinson's disease.

METHODS

Eighty non-demented Parkinson's disease patients and 60 healthy controls participated in the study. Attention was assessed in a computer-controlled reaction time paradigm. The test session comprised a simple reaction time task and four choice reaction time tasks: a go/no-go task, a one-dimension, focused-attention task, a two-dimension, divided-attention task and an alternating task. Performance was assessed by composite measures: (i) cognitive reaction time, corresponding to the difference between the simple reaction time and the choice reaction time in the given condition, and (ii) reaction time variability, corresponding to the sum of the coefficients of variance of the reaction times. Accuracy was also considered.

RESULTS

Apart from an overall slowing and greater reaction time variability, Parkinson's disease patients were only significantly impaired in the alternating condition. This set-shifting impairment was associated with their performance in the go/no-go and divided-attention conditions.

CONCLUSION

Our systematic assessment of the different attentional subcomponents revealed that mental flexibility is particularly impaired in non-demented Parkinson's disease patients.

Nonmotor outcomes in Parkinson's disease: is deep brain stimulation better than dopamine replacement therapy?

Nonmotor symptoms are an integral part of Parkinson's disease and cause significant morbidity. Pharmacological therapy helps alleviate the disease but produces nonmotor manifestations. While deep brain stimulation (DBS) has emerged as the treatment of choice for motor dysfunction, the effect on nonmotor symptoms is not well known. Compared with pharmacological therapy, bilateral subthalamic nucleus (STN)-DBS or globus pallidum interna (GPi)-DBS has significant beneficial effects on pain, sleep, gastrointestinal and urological symptoms. STN-DBS is associated with a mild worsening in verbal fluency while GPi-DBS has no effect on cognition. STN-DBS may improve cardiovascular autonomic disturbances by reducing the dose of dopaminergic drugs. Because the motor effects of STN-DBS and GPi-DBS appear to be similar, nonmotor symptoms may determine the target choice in surgery of future patients.

Cognitive assessment instruments in Parkinson's disease patients undergoing deep brain stimulation

Deep Brain Stimulation (DBS) is a widely used surgical technique in individuals with Parkinson's disease (PD) that can lead to significant reductions in motor symptoms.