Comparative study of the substantia nigra echogenicity and 123I-Ioflupane SPECT in patients with synucleinopathies with and without REM sleep behavior disorder.

OBJECTIVES: Hyperechogenicity of the substantia nigra (SN) and abnormal dopamine transporter-single-photon emission computed tomography (DAT-SPECT) are biomarkers commonly used in the assessment of prodromal synucleinopathy. Our goals were as follows: (1) to compare echogenicity of SN in idiopathic rapid eye movement (REM) behavior disorder (iRBD), Parkinson's disease (PD) without RBD (PD-noRBD), PD with RBD (PD + RBD), and control subjects; and (2) to examine association between SN degeneration assessed by DAT-SPECT and SN echogenicity. PATIENTS/METHODS: A total of 61 subjects with confirmed iRBD were examined using Movement Disorders Society-unified PD rating scale (MDS-UPDRS), TCS (transcranial sonography) and DAT-SPECT. The results were compared with 44 patients with PD (25% PD + RBD) and with 120 age-matched healthy subjects. RESULTS AND CONCLUSION: The abnormal SN area was found in 75.5% PD, 23% iRBD and 7.3% controls. Median SN echogenicity area in PD (0.27 ± 0.22 cm2) was higher compared to iRBD (0.07 ± 0.07 cm2; p < 0.0001) and controls (0.05 ± 0.03 cm2; p < 0.0001). SN echogenicity in PD + RBD was not significantly different from PD-noRBD (0.30 vs. 0.22, p = 0.15). Abnormal DAT-SPECT was found in 16 iRBD (25.4%) and 44 PD subjects (100%). No correlation between the larger SN area and corresponding putaminal binding index was found in iRBD (r = -0.13, p = 0.29), nor in PD (r = -0.19, p = 0.22). The results of our study showed that: (1) SN echogenicity area in iRBD was higher compared to controls, but the hyperechogenicity was present only in a minority of iRBD patients; (2) SN echogenicity and DAT-SPECT binding index did not correlate in either group; and (3) SN echogenicity does not differ between PD with/without RBD.

Automatic substantia nigra segmentation in neuromelanin-sensitive MRI by deep neural network in patients with prodromal and manifest synucleinopathy.

Neuromelanin (NM) is a black pigment located in the brain in substantia nigra pars compacta (SN) and locus coeruleus. Its loss is directly connected to the loss of nerve cells in this part of the brain, which plays a role in Parkinson's Disease. Magnetic resonance imaging (MRI) is an ideal tool to monitor the amount of NM in the brain in vivo. The aim of the study was the development of tools and methodology for the quantification of NM in a special neuromelanin-sensitive MRI images. The first approach was done by creating regions of interest, corresponding to the anatomical position of SN based on an anatomical atlas and determining signal intensity threshold. By linking the anatomical and signal intensity information, we were able to segment the SN. As a second approach, the neural network U-Net was used for the segmentation of SN. Subsequently, the volume characterizing the amount of NM in the SN region was calculated. To verify the method and the assumptions, data available from various patient groups were correlated. The main benefit of this approach is the observer-independency of quantification and facilitation of the image processing process and subsequent quantification compared to the manual approach. It is ideal for automatic processing many image sets in one batch.

Correction to: Pupillometry as an indicator of L-DOPA dosages in Parkinson's disease patients.

Unfortunately, original article has been published without acknowledgement section.

Diagnostic exome sequencing in early-onset Parkinson's disease confirms VPS13C as a rare cause of autosomal-recessive Parkinson's disease.

Parkinson's disease (PD) is a genetically heterogeneous disorder and new putative disease genes are discovered constantly. Therefore, whole-exome sequencing could be an efficient approach to genetic testing in PD. To evaluate its performance in early-onset sporadic PD, we performed diagnostic exome sequencing in 80 individuals with manifestation of PD symptoms at age 40 or earlier and a negative family history of PD. Variants in validated and candidate disease genes and risk factors for PD and atypical Parkinson syndromes were annotated, followed by further analysis for selected variants. We detected pathogenic variants in Mendelian genes in 6.25% of cases and high-impact risk factor variants in GBA in 5% of cases, resulting in overall maximum diagnostic yield of 11.25%. One individual was compound heterozygous for variants affecting canonical splice sites in VPS13C, confirming the causal role of protein-truncating variants in this gene linked to autosomal-recessive early-onset PD. Despite the low diagnostic yield of exome sequencing in sporadic early-onset PD, the confirmation of the recently discovered VPS13C gene highlights its advantage over using predefined gene panels.

Pupillometry as an indicator of L-DOPA dosages in Parkinson's disease patients.

Dopamine was shown to induce mydriasis by excitation of alpha-adrenergic receptors at the dilator pupillae muscle. Pupilla diameter may thus serve as an indirect measure of peripheral pharmacokinetics of L-DOPA and dopamine. The aim of this study is to evaluate the effect of L-DOPA dosage on pupillometric parameters in Parkinson's disease (PD) patients. Sixteen PD patients and 14 healthy control subjects (CS) were studied. The statistical analysis revealed significant differences between CS and PD patients for the mean maximum and minimum pupil diameters (p = 0.017, p = 0.028, respectively), with higher values found in PD. Moreover, a significant dose-response relationship was found between the maximum pupil diameter and both the morning L-DOPA dose (R 2 = 0.78) and the total daily L-DOPA dose (R 2 = 0.93). A sigmoid-shaped curve best describes the dose-response relationship, with a ceiling effect at about 400 mg L-DOPA daily dose. In conclusion, measuring pupillometric parameters represents a sensitive tool for non-invasive evaluation of the peripheral effect of L-DOPA, especially with daily doses below 400 mg L-DOPA.

GABA spectra and remote distractor effect in progressive supranuclear palsy: A pilot study.

Disturbances of the gamma-aminobutyric-acid (GABA) system have been suspected of contributing to the pathophysiology of progressive supranuclear palsy (PSP). The ability to rapidly resolve competitive action decisions, such as shifting the gaze to one particular stimulus rather than another, can be predicted by the concentration of GABA in the region of the frontal cortex relevant to eye movements. For this reason, our study measured GABA levels in seven PSP patients and eight healthy controls, using proton magnetic resonance spectroscopy, and assessed the relationship of these measurements to the remote distractor effect (RDE), an eye-movement paradigm investigating competitive action decisions. No significant differences were found in either frontal-eye-field GABA levels or RDE between PSP patients and controls.

Cognitive sequelae of methanol poisoning involve executive dysfunction and memory impairment in cross-sectional and long-term perspective.

Methanol poisoning leads to lesions in the basal ganglia and subcortical white matter, as well as to demyelination and atrophy of the optic nerve. However, information regarding cognitive deficits in a large methanol sample is lacking. The principal aim of the present study was to identify the cognitive sequelae of methanol poisoning and their morphological correlates. A sample of 50 patients (METH; age 48 ± 13 years), 3-8 months after methanol poisoning, and 57 control subjects (CS; age 49 ± 13 years) were administered a neuropsychological battery. Forty-six patients were followed in 2 years' perspective. Patients additionally underwent 1.5T magnetic resonance imaging (MRI). Three biochemical and toxicological metabolic markers and a questionnaire regarding alcohol abuse facilitated the classification of 24 patients with methanol poisoning without alcohol abuse (METHna) and 22 patients with methanol poisoning and alcohol abuse (METHa). All groups were compared to a control group of similar size, and matched for age, education, premorbid intelligence level, global cognitive performance, and level of depressive symptoms. Using hierarchical multiple regression we found significant differences between METH and CS, especially in executive and memory domains. METHa showed a similar pattern of cognitive impairment with generally more severe executive dysfunction. Moreover, all METH patients with extensive involvement on brain MRI (lesions in ≥2 anatomical regions) had a more severe cognitive impairment. From a longitudinal perspective, we did not find any changes in their cognitive functioning after 2 years' follow-up. Our findings suggest that methanol poisoning is associated with executive dysfunction and explicit memory impairment, supposedly due to basal ganglia dysfunction and disruption of frontostriatal circuitry proportional to the number of brain lesions, and that these changes are persistent after 2 years' follow-up.

EFNS/MDS-ES/ENS [corrected] recommendations for the diagnosis of Parkinson's disease.

BACKGROUND: A Task Force was convened by the EFNS/MDS-ES Scientist Panel on Parkinson's disease (PD) and other movement disorders to systemically review relevant publications on the diagnosis of PD. METHODS: Following the EFNS instruction for the preparation of neurological diagnostic guidelines, recommendation levels have been generated for diagnostic criteria and investigations. RESULTS: For the clinical diagnosis, we recommend the use of the Queen Square Brain Bank criteria (Level B). Genetic testing for specific mutations is recommended on an individual basis (Level B), taking into account specific features (i.e. family history and age of onset). We recommend olfactory testing to differentiate PD from other parkinsonian disorders including recessive forms (Level A). Screening for pre-motor PD with olfactory testing requires additional tests due to limited specificity. Drug challenge tests are not recommended for the diagnosis in de novo parkinsonian patients. There is an insufficient evidence to support their role in the differential diagnosis between PD and other parkinsonian syndromes. We recommend an assessment of cognition and a screening for REM sleep behaviour disorder, psychotic manifestations and severe depression in the initial evaluation of suspected PD cases (Level A). Transcranial sonography is recommended for the differentiation of PD from atypical and secondary parkinsonian disorders (Level A), for the early diagnosis of PD and in the detection of subjects at risk for PD (Level A), although the technique is so far not universally used and requires some expertise. Because specificity of TCS for the development of PD is limited, TCS should be used in conjunction with other screening tests. Conventional magnetic resonance imaging and diffusion-weighted imaging at 1.5 T are recommended as neuroimaging tools that can support a diagnosis of multiple system atrophy (MSA) or progressive supranuclear palsy versus PD on the basis of regional atrophy and signal change as well as diffusivity patterns (Level A). DaTscan SPECT is registered in Europe and the United States for the differential diagnosis between degenerative parkinsonisms and essential tremor (Level A). More specifically, DaTscan is indicated in the presence of significant diagnostic uncertainty such as parkinsonism associated with neuroleptic exposure and atypical tremor manifestations such as isolated unilateral postural tremor. Studies of [(123) I]MIBG/SPECT cardiac uptake may be used to identify patients with PD versus controls and MSA patients (Level A). All other SPECT imaging studies do not fulfil registration standards and cannot be recommended for routine clinical use. At the moment, no conclusion can be drawn as to diagnostic efficacy of autonomic function tests, neurophysiological tests and positron emission tomography imaging in PD. CONCLUSIONS: The diagnosis of PD is still largely based on the correct identification of its clinical features. Selected investigations (genetic, olfactory, and neuroimaging studies) have an ancillary role in confirming the diagnosis, and some of them could be possibly used in the near future to identify subjects in a pre-symptomatic phase of the disease.

Quantitative acoustic measurements for characterization of speech and voice disorders in early untreated Parkinson's disease.

An assessment of vocal impairment is presented for separating healthy people from persons with early untreated Parkinson's disease (PD). This study's main purpose was to (a) determine whether voice and speech disorder are present from early stages of PD before starting dopaminergic pharmacotherapy, (b) ascertain the specific characteristics of the PD-related vocal impairment, (c) identify PD-related acoustic signatures for the major part of traditional clinically used measurement methods with respect to their automatic assessment, and (d) design new automatic measurement methods of articulation. The varied speech data were collected from 46 Czech native speakers, 23 with PD. Subsequently, 19 representative measurements were pre-selected, and Wald sequential analysis was then applied to assess the efficiency of each measure and the extent of vocal impairment of each subject. It was found that measurement of the fundamental frequency variations applied to two selected tasks was the best method for separating healthy from PD subjects. On the basis of objective acoustic measures, statistical decision-making theory, and validation from practicing speech therapists, it has been demonstrated that 78% of early untreated PD subjects indicate some form of vocal impairment. The speech defects thus uncovered differ individually in various characteristics including phonation, articulation, and prosody.

Deep brain stimulation of the subthalamic nucleus and cognitive functions in Parkinson's disease.

Deep brain stimulation of the subthalamic nucleus (DBS/STN) is an effective treatment for motor symptoms in advanced Parkinson's disease (PD). However, it is less clear how DBS/STN affects cognitive functions. We investigated 19 PD patients (13 male, 6 female, mean age 57 +/- 6, mean PD duration 15 +/- 4 years) who received bilateral DBS/STN. Neuropsychological assessment was done before the surgery and at least 12 months after DBS implantation. The patients were examined in their optimal motor status. Global cognitive performance measured by Mattis Dementia Rating Scale was not significantly changed after DBS STN. The performance in Wechsler Memory Scale III decreased in the subtest Logical Memory, in delayed recall (p < 0.05) and in recognition (p < 0.05). In Stroop Test, the performance worsened in the second (p < 0.05), and third condition (p < 0.01) measuring interference and ability to suppress automatic reactions. In conclusion, patients treated by DBS/STN tend to worsen in executive functions and in logical memory.

A new botulinum toxin type A free of complexing proteins for treatment of cervical dystonia.

A new botulinum toxin type A free of complexing proteins (NT 201) was compared with BOTOX in patients with cervical dystonia by means of a double-blind noninferiority trial. Four hundred sixty-three patients received IM injections of 70 to 300 U of NT 201 or BOTOX and were followed up over 16 weeks. The study clearly shows that NT 201 is at least as effective and safe as BOTOX.

[Organ changes induced by ergot derivative dopamine agonist drugs: time to change treatment guidelines in Parkinson's disease?]. / Orgánové komplikace navozené ergotovými agonisty dopaminu--cas na zmenu lécebných doporucení?

Ergot derivative dopamine agonists, e.g. pergolide, bromocriptine, dihydroergocriptine used in treatment of Parkinson's disease can cause pleural, pericardial, retroperitoneal and valvular fibrotic changes. Case No 1: A 56-year-old woman with PD was treated with pergolide 3mg/24h since July 2002. In June 2003, edema of lower extremities was first noticed and echocardiography found a minor mitral regurgitation without any morphological changes of the valve. In January 2004, left- sided cardiac failure rapidly developed and echocardiography revealed multivalvular insufficiency with predominating severe mitral regurgitation. Mitral valve replacement was performed and pergolide was changed to ropinirole. Until now, neither cardiac functions nor motor status are sufficiently compensated. Case No 2: A 66-year-old-man with PD since 1996 was treated with pergolide 3 mg/day since 1999. In the beginning of 2004, leg edema appeared. On examination, bilateral hydronephrosis with ureteric strictures and incipient renal insufficiency was found. Bilateral ureteroplasty was performed and the histology showed periureteric fibrosis. Treatment with steroids was initiated and pergolide was changed to pramipexole. Despite the treatment, the fibrosis progressed, requiring ureteral stenting. Based on the literature review and on our own experience, we propose following guidelines to minimize the risk of complications: A. Not to use EAD as the first-line dopamine agonists. B. Regularly follow all patients treated with EAD, especially monitor the majorsymptoms: dyspnea, cough, fatigue, leg edema (also asymmetric), symptoms of urinary outflow obstruction, cardiac insufficiency, chest pain, heart murmur. An elevated ESR, C-reactive protein or anemia support the diagnosis. C. All symptomatic patients should undergo workup for serosal fibrosis (according to type of complication): chest X-ray or CT scan, spirometry, renal functions, renal ultrasound, CT of retroperitoneum. D. Before the introduction of EAD therapy, examine the renal functions, perform chest X-ray and echocardiography. Screening echocardiography should be performed in 3-6 months and subsequently in every 6-12 months.

Comparison of alpha-dihydroergocryptine and levodopa monotherapy in Parkinson's disease: assessment of changes in DAT binding with [123I]IPT SPECT.

Putative neurotoxic actions of levodopa and neuroprotective effects of dopamine agonists, as indicated by laboratory and animal studies, provide the rationale to study their effect on the progression of Parkinson's disease. Aim of this pilot study was to compare the effects of monotherapy with the dopamine agonist alpha-dihydroergocryptine (DEC) versus monotherapy with levodopa on nigrostriatal dopaminergic neurons as measured with dopamine transporter (DAT) SPECT. 25 PD patients (H&Y stages 1 to 2.5) entered this study and were treated in a randomized fashion either with DEC (101+/-39 mg) or levodopa (369+/-51 mg) monotherapy. 16/25 patients (8 per group) terminated the study after 52 weeks. In each patient SPECT investigations with [123I]IPT were performed at baseline and after 52 weeks to assess changes of specific DAT binding over time. Changes in clinical symptoms were assessed by UPDRS score. The mean annual decline rate in striatal IPT-binding was lower in the DEC group (8.4%) compared to the levodopa group (10.4%). The difference was most accentuated in the putamen (DEC: 7.3%; levodopa: 16.2%; p = 0.16). Due to the small sample size and the relatively short observation period, however, group differences did not reach a statistical significant level. The results of this pilot study suggest that as compared to levodopa monotherapy DEC may have beneficial effects on decline of dopamine transporter binding similar to those recently described for pramipexole.

Driving in Parkinson's disease - a health hazard?

BACKGROUND: The driving safety of Parkinson's disease (PD) patients has lately been questioned after several authors reported road accidents caused by sleep attacks in PD patients on dopaminergic medication. OBJECTIVES: To determine 1) whether PD patients in general and those on dopaminergic medication in particular are especially prone to cause severe road accidents and 2) whether there are PD symptoms or dopaminergic side effects with the potential to compromise driving safety. DATA SOURCE: Relevant articles were identified by electronic search of biomedical databases (1966-2002: MEDLINE, EMBASE, PASCAL, PUBMED), the Cochrane Controlled Trials Register, and reference lists of located articles. RESULTS: Despite frequent occurrence of potentially hazardous dopaminergic side effects (2-57 %) and disabling parkinsonian non-motor and motor disabilities (16-63 %), the two existing studies on accident rates suggest that PD patients are not more prone to cause road accidents than the rest of the population. Five further reports including 1346 patients and focusing on dopaminergically induced sleep attacks provided comparably low accident figures (yearly incidence: 0%-2%). Because of low figures meta-analysis was intended but finally deemed inappropriate as the methodology of included studies varied greatly and was frequently flawed. CONCLUSION: Further prospective community-based well designed studies on accident risk in PD patients are needed to provide evidence based driving recommendations.

Influence of age, gender, education and dexterity on upper limb motor performance in Parkinsonian patients and healthy controls.

Finger tapping, the most widely used test for evaluating motor dysfunction in Parkinson's disease (PD), was found to react sensitively to disease specific factors like disease severity and changes in medication. A possible interference caused by disease unrelated demographic factors--age, gender, education and dexterity--however has not yet been studied systematically. Various components of tapping performance of 187 healthy subjects and 200 PD patients were assessed by means of the BRAIN TEST, a digitalized test battery. The effects of demographic factors--above all education and age--were found to be significant. These influences generally affect different aspects of movement to a different extent, with speed and akinesia being affected more severely than dysmetria and arrhythmokinesis. Our study suggests that whenever precise assement of upper limb motor performance is needed, specific corrections for these demographic factors in both healthy controls and PD patients are necessary.

East-west differences in the organization of botulinum toxin use in nine Central European countries.

Availability and quality of expensive treatment modalities such as botulinum toxin (BTX) largely depend on organizational aspects such as costs, reimbursement by insurance companies, expertise and facilities for expert training, and the propagation of research. To investigate which determinants influence the organization of BTX' use throughout nine Central European countries (Austria, Croatia, Czech Republic, Germany, Hungary, Italy, Slovakia, Slovenia and Switzerland) we sent out questionnaires to leading BTX experts and consulted data banks of manufacturers and bulletins of international organizations. In Western European countries, there is a tendency for users to organize themselves in formal groups and to concentrate on research whereas the way how BTX is provided is diverse regarding qualifications of specialists and institutions. In the post-communist Eastern European countries, we found a tendency towards a centralized system of reimbursement and BTX treatment seems to be more in the hands of neurologists than any other specialists. Strong correlations were observed between the number of BTX centres, degree of organization of user groups and number of scientific publications, on the one hand, and parameters of healthcare performance and socioeconomic determinants, on the other. Our study suggests that in the nine countries surveyed, organizational aspects of BTX use vary considerably, whilst similarities are based mainly on socioeconomic rather than socio-demographic determinants.

Changes of event related potential and cognitive processes in patients with subclinical hypothyroidism after thyroxine treatment.

OBJECTIVE: Recently, it has been repeatedly shown that patients with subclinical hypothyroidism (SH) formerly considered as completely symptom free, may have numerous minimal, often non-specific subjective complaints, and that in those patients it is possible to prove many subtle but objective deviations. We decided to quantify whether there are event related potential (ERP) deviations as electrophysiological markers of cognitive activity in patients with SH and whether ERP could be influenced by thyroxine treatment leading to normalization of TSH level in serum. SUBJECTS AND DESIGN: Event related potential (ERP) was examined in thirty one patients (mean age 52 +/- 12.5 years) with SH and without any other endocrine or metabolic diseases and in 29 subjects of the control group. From 31 patients 20 women (mean age 61.8 +/-6.8 years) were selected and divided into a group of 10 women treated six months with L-thyroxine until the normalization of TSH and remaining 10 women receiving placebo. ERP examination was repeated and all such patients also underwent neuropsychological examination consisting of the Wechsler Memory Scale and the MMPI/100 (Minnesota Multiphasic Personality Inventory). The interval between the diagnosis of SH and final evaluation of treatment was 16 months. RESULTS: In SH thyroxine treated patients the average P3 wave latency was 374 ms (SD 40.6), while in placebo group it was 340 ms (SD 32.3. P<0.01). In addition, the treatment with thyroxine normalized the TSH level resulted in a decrease of P3 wave latency from 374 +/- 36.3 ms to 343 +/- 16.3 ms (P<0.01). However, in the placebo group such changes were not observed, the latency of P3 being 387 +/- 24.3 ms at the beginning and 379 +/- 36.5 ms at the end of observation period. No significant correlations between P3 wave latency and thyroid parameters were found. In thyroxine treated group a significant improvement in verbal memory (P<0.01), visual memory (P<0.01) and total memory scores (P<0.01) was found, while no changes in these parameters were observed in the placebo group. No significant differences were found in the MMPI test evaluation. CONCLUSION: SH patients had significantly longer P3 wave latency in ERP examination as compared to healthy individuals which gives evidence for impaired cognitive functions in SH patients. In these patients the normalization of TSH level by thyroxine treatment resulted also in the normalization of P3 wave latency. In addition, also verbal, visual and total memory scores improved significantly with the TSH normalization.

Rat spatial memory tasks adapted for humans: characterization in subjects with intact brain and subjects with selective medial temporal lobe thermal lesions.

In the present paper we describe five tests, 3 of which were designed to be similar to tasks used with rodents. Results obtained from control subjects, patients with selective thermo-coagulation lesions to the medial temporal lobe and results from non-human primates and rodents are discussed. The tests involve memory for spatial locations acquired by moving around in a room, memory for objects subjects interacted with, or memory for objects and their locations. Two of the spatial memory tasks were designed specifically as analogs of the Morris water task and the 8-arm radial-maze tasks used with rats. The Morris water task was modeled by hiding a sensor under the carpet of a room (Invisible Sensor Task). Subjects had to learn its location by using an array of visual cues available in the room. A path integration task was developed in order to study the non-visual acquisition of a cognitive representation of the spatial location of objects. In the non-visual spatial memory task, we blindfolded subjects and led them to a room where they had to find 3 objects and remember their locations. We designed an object location task by placing 4 objects in a room that subjects observed for later recall of their locations. A recognition task, and a novelty detection task were given subsequent to the recall task. An 8-arm radial-maze was recreated by placing stands at equal distance from each other around the room, and asking subjects to visit each stand once, from a central point. A non-spatial working memory task was designed to be the non-spatial equivalent of the radial maze. Search paths recorded on the first trial of the Invisible Sensor Task, when subjects search for the target by trial and error are reported. An analysis of the search paths revealed that patients with lesions to the right or left hippocampus or parahippocampal cortex employed the same type of search strategies as normal controls did, showing similarities and differences to the search behavior recorded in rats. Interestingly, patients with lesions that included the right parahippocampal cortex were impaired relative to patients with lesions to the right hippocampus that spared the parahippocampal cortex, when recall of the sensor was tested after a 30 min delay (Bohbot et al. 1998). No differences were obtained between control subjects and patients with selective thermal lesions to the medial temporal lobe, when tested on the radial-maze, the non-spatial analogue to the radial-maze and the path integration tasks. Differences in methodological procedures, learning strategies and lesion location could account for some of the discrepant results between humans and non-human species. Patients with lesions to the right hippocampus, irrespective of whether the right parahippocampal cortex was spared or damaged, had difficulties remembering the particular configuration and identity of objects in the novelty detection of the object location task. This supports the role of the human right hippocampus for spatial memory, in this case, involving memory for the location of elements in the room; learning known to require the hippocampus in the rat.

Functional magnetic resonance imaging during deep brain stimulation: a pilot study in four patients with Parkinson's disease.

Functional magnetic resonance imaging (fMRI) was performed in patients with Parkinson's disease during deep brain stimulation of the subthalamic nucleus (three patients) and during deep brain stimulation of the ventral intermedius nucleus of the thalamus (one patient). All showed an increase in blood oxygenation level-dependent signal in the subcortical regions ipsilateral to the stimulated nucleus. This effect cannot be simply explained by a mechanism of depolarization blockade; rather, it is caused by overstimulation of the target nucleus, resulting in the suppression of its spontaneous activity. We confirm that fMRI during deep brain stimulation is a safe method with considerable potential for elucidating the functional connectivity of the stimulated nuclei.