Enhancing Attentional Performance in Parkinson's Disease: The Impact of Combined Deep Brain Stimulation of the Substantia Nigra Pars Reticulata and the Subthalamic Nucleus.

OBJECTIVE: The concomitant stimulation of the subthalamic nucleus and the substantia nigra pars reticulata is a promising approach to improve treatment of refractory axial symptoms in Parkinson's disease. While dual stimulation of the subthalamic nucleus and the substantia nigra pars reticulata has previously shown beneficial effects on gait, the role of the substantia nigra, a crucial component of the basal ganglia circuitry, in cognitive functions such as attention and executive control remains underexplored. This study aimed to investigate the impact of selective substantia nigra pars reticulata stimulation on attentional performance in patients receiving standard deep brain stimulation of the subthalamic nucleus. METHODS: Twelve patients with bilateral subthalamic nucleus stimulation underwent computerized assessment of attention using a simple reaction time task. Reaction times were assessed under standard stimulation of the subthalamic nucleus versus simultaneous stimulation of the subthalamic nucleus and the substantia nigra pars reticulata. RESULTS: The results revealed a significant improvement in reaction times during the simple reaction time task when patients received dual stimulation compared to standard stimulation. CONCLUSIONS: Our findings provide further evidence for the pivotal role of the substantia nigra pars reticulata in cognitive functions such as attention. Despite the limitations of the study, including a small sample size, our results suggest potential benefits of simultaneous deep brain stimulation of the subthalamic nucleus and the substantia nigra pars reticulata on attentional performance in patients with Parkinson's disease. Further research with larger cohorts is warranted to confirm these findings and better understand the underlying mechanisms.

Sensory nerve conduction studies in infants, children and teenagers - An update.

Objective: Nerve conduction studies (NCS) in children remain technically challenging and depend on the cooperation of the child. Motor NCS are not compromised by analgosedation but data for sensory NCS are lacking. Here, we ask whether sensory NCS is influenced by analgosedation. We also compare the present data with NCS studies from the 1990s regarding anthropometric acceleration of the contemporary paediatric population. Methods: Sensory NCS of the median nerve and sural nerve were performed in 182 healthy subjects aged 1 to 18 years during general anaesthesia and in 47 of them without analgosedation. Results: Sensory NCS was not influenced by midazolam or propofol. The sensory nerve action potential (SNAP) amplitude and the nerve conduction velocity (NCV) of the sural nerve as well as the SNAP of the median nerve show no significant age dependence in age range 1-18 years. The sensory NCV of the median nerve increased age-dependent. Conclusions: In clinical practice, analgosedation can be used for diagnostic NCS. Sensory NCS data show no relevant secular trend over the last 30 years. Differences due to technical inconsistency predominate. Significance: Analgosedation can improve diagnostic quality of sensory NCS in children. Additionally, we provide sensory NCS values from a large pediatric cohort.

Deep brain stimulation of the ventrointermediate nucleus of the thalamus to treat essential tremor improves motor sequence learning.

The network of brain structures engaged in motor sequence learning comprises the same structures as those involved in tremor, including basal ganglia, cerebellum, thalamus, and motor cortex. Deep brain stimulation (DBS) of the ventrointermediate nucleus of the thalamus (VIM) reduces tremor, but the effects on motor sequence learning are unknown. We investigated whether VIM stimulation has an impact on motor sequence learning and hypothesized that stimulation effects depend on the laterality of electrode location. Twenty patients (age: 38-81 years; 12 female) with VIM electrodes implanted to treat essential tremor (ET) successfully performed a serial reaction time task, varying whether the stimuli followed a repeating pattern or were selected at random, during which VIM-DBS was either on or off. Analyses of variance were applied to evaluate motor sequence learning performance according to reaction times (RTs) and accuracy. An interaction was observed between whether the sequence was repeated or random and whether VIM-DBS was on or off (F[1,18] = 7.89, p = .012). Motor sequence learning, reflected by reduced RTs for repeated sequences, was greater with DBS on than off (T[19] = 2.34, p = .031). Stimulation location correlated with the degree of motor learning, with greater motor learning when stimulation targeted the lateral VIM (n = 23, ρ = 0.46; p = .027). These results demonstrate the beneficial effects of VIM-DBS on motor sequence learning in ET patients, particularly with lateral VIM electrode location, and provide evidence for a role for the VIM in motor sequence learning.

Brain biopsy in patients with CLIPPERS syndrome: why and when.

CLIPPERS (chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids) is an inflammatory disorder of the central nervous system (CNS), predominantly involving the brainstem with a characteristic magnetic resonance imaging (MRI) appearance and clinical and radiological responsiveness to glucocorticosteroids. Yet diagnostic biomarkers are missing and other immune-mediated, (para-) infectious and malignant causes mimic CLIPPERS-like MRI presentations. We report the case of a 51-year-old male patient with CLIPPERS who repeatedly responded well to high-dose corticosteroids. After 7 months, however, treatment failed, and he had a biopsy-confirmed diagnosis of a CNS B-cell lymphoma. Clinical and MRI signs of CLIPPERS include a wide spectrum of differential diagnoses which often arise only later during the course of disease. Similar to the case presented here, delayed diagnosis and specific therapy may contribute to an unfavorable outcome. Hence, we propose that in the absence of other diagnostic markers, brain biopsy should be performed as early as possible in CLIPPERS patients.

Neurofilament Levels Are Reflecting the Loss of Presynaptic Dopamine Receptors in Movement Disorders.

Aims: Neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH) are biomarkers for neuroaxonal damage. We assessed whether NfL and other biomarker levels in the CSF are correlated to the loss of presynaptic dopamine transporters in neurons as detected with dopamine transporter SPECT (DaTscan). Methods: We retrospectively identified 47 patients (17 Alzheimer's dementia, 10 idiopathic Parkinson's disease, 7 Lewy body dementia, 13 progressive supranuclear palsy or corticobasal degeneration) who received a DaTscan and a lumbar puncture. DaTscan imaging was performed according to current guidelines, and z-scores indicating the decrease in uptake were software based calculated for the nucleus caudatus and putamen. The CSF biomarkers progranulin, total-tau, alpha-synuclein, NfL, and pNfH were correlated with the z-scores. Results: DaTscan results in AD patients did not correlate with any biomarker. Subsuming every movement disorder with nigrostriatal neurodegeneration resulted in a strong correlation between putamen/nucleus caudatus and NfL (nucleus caudatus right p < 0.01, putamen right p < 0.05, left p < 0.05) and between pNfH and putamen (right p < 0.05; left p < 0.042). Subdividing in disease cohorts did not reveal significant correlations. Progranulin, alpha-synuclein, and total-tau did not correlate with DaTscan results. Conclusion: We show a strong correlation of NfL and pNfH with pathological changes in presynaptic dopamine transporter density in the putamen concomitant to nigrostriatal degeneration. This correlation might explain the reported correlation of impaired motor functions in PD and NfL as seen before, despite the pathological heterogeneity of these diseases.

The LC-NE system as a potential target for neuromodulation to ameliorate non-motor symptoms in Parkinson's disease.

Parkinson's disease (PD) is associated with severe motor symptoms but also with several non-motor symptoms (NMS). A substantial reduction of norepinephrine (NE) levels in various brain regions reflecting an extensive loss of innervation from the LC has been assumed as causal for the development of NMS and specifically of attentional impairments in PD. Transcutaneous auricular vagus nerve stimulation (taVNS) is a new, non-invasive neurostimulation method supposed to modulate the LC-NE system in humans. In the current opinion paper, we introduce taVNS as a systemic approach to directly affect NE neurotransmission in healthy as well as clinical populations and discuss its potential as therapeutic option for the treatment of NMS, specifically attentional deficits, in patients with PD. Here, we first describe the LC-NE system and discuss how LC-NE dysfunction might affects cognition in PD before detailing the mode of action of taVNS and proposing its use to modulate cognitive deficits in these patients.

Neuromodulation of the subthalamic nucleus in Parkinson's disease: the effect of fiber tract stimulation on tremor control.

BACKGROUND: Therapeutic effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) may in parts be attributed to the stimulation of white matter near the targeted structure. The dentato-rubro-thalamic (DRT) tract supposed to improve tremor control in patients with essential tremor could be one candidate structure. The aim of this study was to investigate the effect of stimulation proximity to the DRT on tremor control in PD patients treated with STN-DBS. METHODS: For this retrospective analysis, we included 36 consecutive patients (median age 65.5 years) treated with STN-DBS for disabling motor symptoms including tremor. Stereotactic implantation of DBS electrodes into the motor area of the STN was performed using direct MRI-based targeting and intraoperative microelectrode recording. Tremor severity was assessed preoperatively and at regular intervals postoperatively (Unified Parkinson's Disease Rating Scale III). The DRT was visualized in 60 hemispheres after probabilistic fiber tracking (3-T MRI). The position of active electrode contacts was verified on intraoperative stereotactic X-rays and postoperative CT images after co-registration with 3D treatment planning MRI/CT images. We determined the shortest distance of active contacts to the ipsilateral DRT tracts on perpendicular view slices and correlated this value with tremor change percentage. RESULTS: Twelve patients had unilateral tremor only, and accordingly, 12 hemispheres were excluded from further imaging analysis. The remaining 60 hemispheres were associated with contralateral resting tremor. Active brain electrode contacts leading to resting tremor improvement (46 hemispheres) had a significantly shorter distance to the DRT (1.6 mm (0.9-2.1) [median (25th-75th percentiles)]) compared with contacts of non-responders (14 hemispheres, distance: 2.8 mm (2-4.6), p < 0.001). CONCLUSION: This retrospective analysis suggests that in STN-DBS, better tremor control in PD patients correlates with the distance of active electrode contacts to the DRT. Tractography may optimize both individually DBS targeting and postoperative adjustment of stimulation parameters.

Neuronal oscillations of the pedunculopontine nucleus in progressive supranuclear palsy: Influence of levodopa and movement.

OBJECTIVE: The pedunculopontine nucleus (PPN) has been proposed as a new deep brain stimulation (DBS) target for the treatment in idiopathic Parkinson's syndrome (IPS) and progressive supranuclear palsy (PSP). In IPS, levodopa has been shown to induce alpha activity in the PPN, indicating a possible physiological role for these oscillations in movement control. Despite shared clinical features, the PPN is more severely affected in PSP than IPS. Here we investigated neuronal oscillations in the PPN in PSP and the influence of levodopa and movement. METHODS: Local field potentials were recorded bilaterally from the PPN of 4 PSP patients at rest, with levodopa and during self-paced leg movements. RESULTS: During rest, levodopa administration was associated with significantly increased alpha and reduced gamma activity in the PPN. Without levodopa, continuous movements were associated with reduced alpha and beta power. These differences between oscillatory power during movement and resting state were not observed with levodopa administration. CONCLUSION: In PSP the changes in neuronal oscillations in the PPN region on levodopa administration are similar to those reported in IPS. The enhancement of lower frequency oscillations in the PPN is possibly influenced by a dopaminergic activation of the striatal pathway and a reduced pallidal inhibition. SIGNIFICANCE: Levodopa influences neuronal oscillations at low and high frequencies in the PPN region in Parkinsonian disorders.

Cerebello-striatal interaction mediates effects of subthalamic nucleus deep brain stimulation in Parkinson's disease.

BACKGROUND: In Parkinson's disease (PD), dopamine replacement therapy (DRT) enhances the effective connectivity of the prefrontal cortex (PFC) and supplementary motor area (SMA). The clinical effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) go beyond DRT effects including highly beneficial tremor suppression. OBJECTIVES: Here, we aimed to determine DBS-related changes of a motor network using resting state fMRI in PD patients with chronic STN DBS. METHODS: In a repeated-measurement design, 26 medicated PD patients (60.9 years (SD 8.9)) were investigated using resting state fMRI while bipolar STN stimulation was (i) active or (ii) switched off, and dynamic causal modelling was subsequently performed. RESULTS: DBS improved the MDS-UPDRS-III score by 26.4% (DBS ON/Med ON vs. DBS OFF/Med ON). Active stimulation resulted in an increased effective connectivity from cerebellum to putamen (p = 0.00118). In addition, there was a stronger coupling from PFC to cerebellum (p = 0.021), as well as from cerebellum to SMA (p = 0.043) on an uncorrected level. Coupling strength from PFC to cerebellum correlated with the DBS-related change of the resting tremor subscore (r = 0.54, p = 0.031). Self-connections increased as a function of DBS in the right PFC, PMC, SMA, M1, thalamus and left cerebellum. CONCLUSIONS: DBS-related improvement of Parkinsonian signs appears to be driven by an interaction between the cerebellum and the putamen. Resting tremor suppression may be related to an enhanced prefronto-cerebellar network. Activation of the mesial premotor loop (PFC-SMA) as seen in DRT may thus be secondary due to the primary modulation of cerebellar networks.

Deep Brain Stimulation of the Subthalamic Nucleus Selectively Modulates Emotion Recognition of Facial Stimuli in Parkinson's Patients.

: Background: Diminished emotion recognition is a known symptom in Parkinson (PD) patients and subthalamic nucleus deep brain stimulation (STN-DBS) has been shown to further deteriorate the processing of especially negative emotions. While emotion recognition generally refers to both, implicit and explicit processing, demonstrations of DBS-influences on implicit processing are sparse. In the present study, we assessed the impact of STN-DBS on explicit and implicit processing for emotional stimuli. METHODS: Under STN-DBS ON and OFF, fourteen PD patients performed an implicit as well as an explicit emotional processing task. To assess implicit emotional processing, patients were tested with a lexical decision task (LTD) combined with an affective priming paradigm, which provides emotional content through the facial eye region. To assess explicit emotional processing, patients additionally explicitly rated the emotional status of eyes and words used in the implicit task. RESULTS: DBS affected explicit emotional processing more than implicit processing with a more pronounced effect on error rates than on reaction speed. STN-DBS generally worsened implicit and explicit processing for disgust stimulus material but improved explicit processing of fear stimuli. CONCLUSIONS: This is the first study demonstrating influences of STN-DBS on explicit and implicit emotion processing in PD patients. While STN stimulation impeded the processing of disgust stimuli, it improved explicit discrimination of fear stimuli.

Long-term outcomes of semi-implantable functional electrical stimulation for central drop foot.

BACKGROUND: Central drop foot is a common problem in patients with stroke or multiple sclerosis (MS). For decades, it has been treated with orthotic devices, keeping the ankle in a fixed position. It has been shown recently that semi-implantable functional electrical stimulation (siFES) of the peroneal nerve can lead to a greater gait velocity increase than orthotic devices immediately after being switched on. Little is known, however, about long-term outcomes over 12 months, and the relationship between quality of life (QoL) and gait speed using siFES has never been reported applying a validated tool. We provide here a report of short (3 months) and long-term (12 months) outcomes for gait speed and QoL. METHODS: Forty-five consecutive patients (91% chronic stroke, 9% MS) with central drop foot received siFES (Actigait®). A 10 m walking test was carried out on day 1 of stimulation (T1), in stimulation ON and OFF conditions, and repeated after 3 (T2) and 12 (T3) months. A 36-item Short Form questionnaire was applied at all three time points. RESULTS: We found a main effect of stimulation on both maximum (p < 0.001) and comfortable gait velocity (p < 0.001) and a main effect of time (p = 0.015) only on maximum gait velocity. There were no significant interactions. Mean maximum gait velocity across the three assessment time points was 0.13 m/s greater with stimulation ON than OFF, and mean comfortable gait velocity was 0.083 m/s faster with stimulation ON than OFF. The increase in maximum gait velocity over time was 0.096 m/s, with post hoc testing revealing a significant increase from T1 to T2 (p = 0.012), which was maintained but not significantly further increased at T3. QoL scores showed a main effect of time (p < 0.001), with post hoc testing revealing an increase from T1 to T2 (p < 0.001), which was maintained at T3 (p < 0.001). Finally, overall absolute QoL scores correlated with the absolute maximum and comfortable gait speeds at T2 and T3, and the increase in overall QoL scores correlated with the increase in comfortable gait velocity from T1 to T3. Pain was reduced at T2 (p < 0.001) and was independent of gait speed but correlated with overall QoL (p < 0.001). CONCLUSIONS: Peroneal siFES increased maximal and comfortable gait velocity and QoL, with the greatest increase in both over the first three months, which was maintained at one year, suggesting that 3 months is an adequate follow-up time. Pain after 3 months correlated with QoL and was independent of gait velocity, suggesting pain as an independent outcome measure in siFES for drop foot.

Electric stimulation of the medial forebrain bundle influences sensorimotor gaiting in humans.

BACKGROUND: Prepulse inhibition (PPI) of the acoustic startle response, a measurement of sensorimotor gaiting, is modulated by monoaminergic, presumably dopaminergic neurotransmission. Disturbances of the dopaminergic system can cause deficient PPI as found in neuropsychiatric diseases. A target specific influence of deep brain stimulation (DBS) on PPI has been shown in animal models of neuropsychiatric disorders. In the present study, three patients with early dementia of Alzheimer type underwent DBS of the median forebrain bundle (MFB) in a compassionate use program to maintain cognitive abilities. This provided us the unique possibility to investigate the effects of different stimulation conditions of DBS of the MFB on PPI in humans. RESULTS: Separate analysis of each patient consistently showed a frequency dependent pattern with a DBS-induced increase of PPI at 60 Hz and unchanged PPI at 20 or 130 Hz, as compared to sham stimulation. CONCLUSIONS: Our data demonstrate that electrical stimulation of the MFB modulates PPI in a frequency-dependent manner. PPI measurement could serve as a potential marker for optimization of DBS settings independent of the patient or the examiner.

Development of evidence-based quality indicators for deep brain stimulation in patients with Parkinson's disease and first year experience of implementation of a nation-wide registry.

INTRODUCTION: Deep Brain Stimulation (DBS) is a complex, invasive and cost-intensive therapy that requires a high level of expertise. To date, data on quality of DBS in clinical routine in the German health care system are lacking. METHODS: The development of evidence-based QIs for DBS in PD patients was performed following a standardized process by a multidisciplinary board between 2014 and 2016. The process was initiated by the German Parkinson Society and followed international recommendations for developing QIs including: a systematic literature search; an appraisal of the published evidence; a consensus-based selection of the QI set; and a pilot study to assess the feasibility in implementing the QIs in clinical routine. RESULTS: A set of 28 QIs for determining the quality of DBS in PD was established by the board covering different dimensions of health care quality (structure, process, and outcome) in different treatment phases of DBS care (pre-operative, peri-operative, and post-operative). Implementation in clinical practice was tested in a pilot study comprising three hospitals delivering DBS care. The feasibility of the QI set was evaluated positively by the participating physicians and hospitals. Mean time to document one patient was 25 min. The German-wide implementation of the defined indicator set within a dedicated quality registry (QualiPa) started in June 2016. CONCLUSION: QIs are a necessary requirement to monitor hospital performance in DBS care. The evidence-based approach to develop the proposed indicator set is expected to assure transparency, acceptance and long-term applicability of the QI set in Germany.

The prevalence of chronic low back pain and lumbar deformities in patients with Parkinson's disease: implications on spinal surgery.

PURPOSE: This observational study was aimed at quantification of low back pain (LBP) in Parkinsonian patients and its morphological correlation. BACKGROUND: Parkinson's disease (PD) is a common disabling condition in the elderly population. Parkinsonian patients frequently are troubled by LBP. Causes for LBP in PD are muscular imbalances by the movement disorder itself and skeletal degeneration. METHODS: Ninety-seven PD patients and 97 controls were inquired about low back pain through the Oswestry Low Back Pain Disability Questionnaire and visual analogue scales. Fifty-four patients with LBP underwent X-ray of the lumbar spine in two planes and flexion-extension views. Parkinson's disease was characterized by stage, disease duration, motor score, lateralization of symptoms and dosage of medication. RESULTS: LBP occurred significantly more frequent in PD (87.6%) compared to controls (62.6%) with longer duration and higher pain intensity. Pain intensity and disability scores were associated with higher PD stages and higher motor scores. Patients with the hypokinetic PD subtype experienced more pain intensity. X-ray of the lumbar spine revealed lumbar arthrosis in 79.6%, scoliosis in 38.8% and spondylolisthesis in 24.1% of PD patients with LBP. Lateralization of scoliosis and PD symptoms were significantly correlated. Only a small portion of PD patients with LBP received specialized orthopaedic treatment. CONCLUSION: LBP and lumbar degeneration are common in PD. Both are related to movement disorder symptoms. The knowledge about musculoskeletal conditions in Parkinson's disease is important for an interdisciplinary conservative or operative treatment decision of LBP. These slides can be retrieved under Electronic Supplementary Material.

Pallidal Stimulation Modulates Pedunculopontine Nuclei in Parkinson's Disease.

BACKGROUND: In advanced Parkinson’s disease, the pedunculopontine nucleus region is thought to be abnormally inhibited by gamma-aminobutyric acid (GABA) ergic inputs from the over-active globus pallidus internus. Recent attempts to boost pedunculopontine nucleus function through deep brain stimulation are promising, but suffer from the incomplete understanding of the physiology of the pedunculopontine nucleus region. METHODS: Local field potentials of the pedunculopontine nucleus region and the globus pallidus internus were recorded and quantitatively analyzed in a patient with Parkinson’s disease. In particular, we compared the local field potentials from the pedunculopontine nucleus region at rest and during deep brain stimulation of the globus pallidus internus. RESULTS: At rest, the spectrum of local field potentials in the globus pallidus internus was mainly characterized by delta-theta and beta frequency activity whereas the spectrum of the pedunculopontine nucleus region was dominated by activity only in the delta and theta band. High-frequency deep brain stimulation of the globus pallidus internus led to increased theta activity in the pedunculopontine nucleus region and enabled information exchange between the left and right pedunculopontine nuclei. Therefore, Conclusions: When applying deep brain stimulation in the globus pallidus internus, its modulatory effect on pedunculopontine nucleus physiology should be taken into account.

Deep brain stimulation of the pedunculopontine nucleus for treatment of gait and balance disorder in progressive supranuclear palsy: Effects of frequency modulations and clinical outcome.

BACKGROUND: The pedunculopontine nucleus has been suggested as a potential deep brain stimulation target for axial symptoms such as gait and balance impairment in idiopathic Parkinson's disease as well as atypical Parkinsonian disorders. METHODS: Seven consecutive patients with progressive supranuclear palsy received bilateral pedunculopontine nucleus deep brain stimulation. Inclusion criteria comprised of the clinical diagnosis of progressive supranuclear palsy, a levodopa-resistant gait and balance disorder, age <75 years, and absence of dementia or major psychiatric co-morbidities. Effects of stimulation frequencies at 8, 20, 60 and 130 Hz on motor scores and gait were assessed. Motor scores were followed up for two years postoperatively. Activities of daily living, frequency of falls, health-related quality of life, cognition and mood at 12 months were compared to baseline parameters. Surgical and stimulation related adverse events were assessed. RESULTS: Bilateral pedunculopontine nucleus deep brain stimulation at 8 Hz significantly improved axial motor symptoms and cyclic gait parameters, while high frequency stimulation did not ameliorate gait and balance but improved hypokinesia. This improvement however did not translate into clinically relevant benefits. Frequency of falls was not reduced. Activities of daily living, quality of life and frontal cognitive functions declined, while mood remained unchanged. CONCLUSION: Bilateral pedunculopontine nucleus deep brain stimulation in progressive supranuclear palsy generates frequency-dependent effects with improvement of cyclic gait parameters at low frequency and amelioration of hypokinesia at high frequency stimulation. However, these effects do not translate into a clinically important improvement.

Bilateral thalamic deep brain stimulation for essential tremor in elderly patients.

The purpose of this study was to assess the influence of age on thalamic deep brain stimulation (DBS) in essential tremor (ET). Tremor, cognition, mood and adverse events in patients with thalamic DBS for ET were evaluated in 26 consecutive patients with established standardized methods for tremor and cognition. Twelve patients <70 and 14 patients ≥70 years were included and followed for 2 years. Clinical outcomes did not differ significantly. DBS seems to be safe and effective for ET independent of age.

Utility of Follow-up Dopamine Transporter SPECT With 123I-FP-CIT in the Diagnostic Workup of Patients With Clinically Uncertain Parkinsonian Syndrome.

PURPOSE: Dopamine transporter SPECT with I-FP-CIT is registered for detection (or exclusion) of nigrostriatal degeneration to support the etiologic classification of parkinsonian syndromes. In case of uncertainty in the interpretation of SPECT findings or unexpected clinical course, follow-up SPECT might be useful. However, the utility of follow-up FP-CIT SPECT has not yet been clarified. METHODS: One hundred forty-one patients (65.1 ± 10.4 years) from 3 sites with follow-up FP-CIT SPECT 22.4 ± 13.7 months after baseline SPECT were included. Retrospective visual interpretation of FP-CIT SPECT scans was performed by 2 experienced readers according to the following 7-point score: "normal," some minor degree of uncertainty due to "mild asymmetry" or mild to moderate "uniform reduction," "Parkinson disease (PD) reduction type 1/2/3," and "atypical reduction." RESULTS: Normal FP-CIT SPECT or PD characteristic reduction was confirmed by follow-up SPECT in all cases (n = 58). Among patients with some minor degree of uncertainty at baseline (n = 65), the majority (72%) did now show abnormalities in follow-up SPECT, but 20% showed clear progression suggesting nigrostriatal degeneration. The latter was very rare at age younger than 60 years. The final categorization as normal or neurodegenerative was not affected by the time delay between baseline and follow-up SPECT. CONCLUSIONS: Follow-up FP-CIT SPECT cannot be generally recommended in case of completely normal baseline SPECT or PD characteristic reduction. It also cannot be recommended in patients younger than 60 years, even in case of some minor degree of uncertainty in the baseline SPECT. There is no evidence to delay follow-up FP-CIT SPECT longer than 12 months.

Effects of deep brain stimulation of the subthalamic nucleus on perceptual decision making.

When faced with difficult decisions, people prefer to stay with the default. This status quo bias often leads to suboptimal choice behavior. Neurophysiological evidence suggests a pivot role of the Subthalamic Nucleus (STN) for overcoming such status quo bias in difficult decisions, but causal evidence is lacking. The present study investigated whether subthalamic deep brain stimulation (DBS) in patients with Parkinson's disease (PD) influences the status quo bias. Eighteen PD patients treated with STN-DBS performed a difficult perceptual decision task incorporating intrinsic status quo option. Patients were tested with (ON) and without (OFF) active STN stimulation. Our results show that DBS of the STN affected perceptual decision making in PD patients depending on the difficulty of decision. STN-DBS improved difficult perceptual decisions due to a selective increase in accuracy (hit rate) that was independent of response bias (no effect on false alarm rate). Furthermore, STN-DBS impacted status quo bias as a function of baseline impulsivity. In impulsive patients, STN-DBS increased the default bias, whereas in less impulsive PD patients, DBS of the STN reduced the status quo bias. In line with our hypothesis, STN-DBS selectively affected the tendency to stick with the default option on difficult decisions, and promoted increased decision accuracy. Moreover, we demonstrate the impact of baseline cognitive abilities on DBS-related performance changes in PD patients.

The whole-brain pattern of magnetic susceptibility perturbations in Parkinson's disease.

Although iron-mediated oxidative stress has been proposed as a potential pathomechanism in Parkinson's disease, the global distribution of iron accumulation in Parkinson's disease has not yet been elucidated. This study used a new magnetic resonance imaging contrast, quantitative susceptibility mapping, and state-of-the-art methods to map for the first time the whole-brain landscape of magnetostatic alterations as a surrogate for iron level changes in n = 25 patients with idiopathic Parkinson's disease versus n = 50 matched controls. In addition to whole-brain analysis, a regional study including sub-segmentation of the substantia nigra into dorsal and ventral regions and qualitative assessment of susceptibility maps in single subjects were also performed. The most remarkable basal ganglia effect was an apparent magnetic susceptibility increase-consistent with iron deposition-in the dorsal substantia nigra, though an effect was also observed in ventral regions. Increased bulk susceptibility, additionally, was detected in rostral pontine areas and in a cortical pattern tightly concordant with known Parkinson's disease distributions of α-synuclein pathology. In contrast, the normally iron-rich cerebellar dentate nucleus returned a susceptibility reduction suggesting decreased iron content. These results are in agreement with previous post-mortem studies in which iron content was evaluated in specific regions of interest; however, extensive neocortical and cerebellar changes constitute a far more complex pattern of iron dysregulation than was anticipated. Such findings also stand in stark contrast to the lack of statistically significant group change using conventional magnetic resonance imaging methods namely voxel-based morphometry, cortical thickness analysis, subcortical volumetry and tract-based diffusion tensor analysis; confirming the potential of whole-brain quantitative susceptibility mapping as an in vivo biomarker in Parkinson's disease.