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The anatomy of the porcine subthalamic nucleus evaluated with immunohistochemistry and design-based stereology.

This study provides a light-microscopic description of the organization, morphology and number of neurons in the subthalamic nucleus (STN) of the Göttingen minipig. It is based on histological material stained with Nissl, Golgi and autometallographic techniques, and employs design-based stereological estimation of the total neuron number. The organization of several neurotransmitters in the STN has been evaluated in histological preparations stained for acetylcholinesterase (AChE) and immunostained for choline acetyltransferase (ChAT), tyrosine hydroxylase (TH), glutamic acid decarboxylase (GAD) and glutamate. In all of the stained preparations the STN appeared as a distinct lens-shaped structure located in the caudal diencephalon, medial to the internal capsule and ventrolateral to the zona incerta. Rostrally, the STN approached the globus pallidus pars interna, whereas caudally the ventromedial part of the STN was adjacent to the rostral part of the substantia nigra pars compacta (SNc), where some of the neurons of the two nuclei merged. The neurons in the STN had medium-sized (25-40 microm) ovoid or fusiform cell bodies, from which three to six large dendrites emanated in a direction predominantly parallel to the long axis of the STN. Immunohistochemistry revealed that most of the subthalamic neurons were glutamatergic and differed significantly in appearance from the large stellate TH-positive cells of the adjacent SNc. Numerous TH-positive bouton-rich fibers traversed the STN. The GAD-staining revealed a large number of terminals within the boundaries of the STN. The STN was highly AChE-positive, reflecting a prominent innervation by ChAT-positive terminals. The total number of subthalamic neurons in one hemisphere was estimated to be approximately 56,000. We conclude that the neuroarchitecture of the porcine STN is similar to primates, including humans, and appears well-suited for further studies examining the role of the STN in movement disorders.

Animals↗

Effects of blockade of metabotropic glutamate receptors in the subthalamic nucleus on haloperidol-induced Parkinsonism in rats.

The present study examined the postural effects of unilaterally local injection of metabotropic glutamate receptor (mGluR) antagonists into the subthalamic nucleus (STN), in rats with haloperidol-induced parkinsonism. In rats which received unilateral microinjections of (+)-alpha-methyl-4-carboxyphenylglycine (MCPG), a selective, subtype-non-specific antagonist of mGluR, but not the vehicle, into the STN, systemic administration of haloperidol induced ipsiversive dystonic posturing. The severity of the dystonic posturing was dose-dependent. However, subtype-specific antagonists of group I, II, or III mGluRs induced no dystonic posturing. The present findings suggest that the activity of the STN under conditions of dopamine blockade is facilitated by blockade of mGluRs in the STN, suggesting that mGluRs exert inhibitory influence on glutamate release in the STN.

Animals↗

Improvements in motor behavioral tests during deep brain stimulation of the subthalamic nucleus in rats with different degrees of unilateral parkinsonism.

Deep brain stimulation (DBS) improves motor performance in Parkinson's disease (PD) patients. To evaluate the effects of subthalamic nucleus (STN)-DBS on impaired motor behavior, we studied improvements in motor performance after delivery of unilateral stimulation to the STN in rats with mild and severe lesions of the nigrostriatal dopamine system caused by injecting 6-hydroxydopamine into the striatum. The rats were trained and performed motor behavioral tests including rotational behavior test, stepping test, and rotarod test before and after receiving DBS. We demonstrated that stimulation at a current strength of 200 microA, which stopped most of the D-amphetamine-induced rotational behaviors in these two groups, improved movement impairments in both the mild and severe groups and that the improvements in the mild group were significantly better than those in the severe group. More experimental and clinical studies are needed to evaluate the efficiency of STN-DBS for different stages of PD.

Amphetamine↗

Effects of subthalamic nucleus stimulation on characteristics of EMG activity underlying reaction time in Parkinson's disease.

We examined the effects of high-frequency deep brain stimulation of the subthalamic nucleus (STN-DBS) on characteristics of electromyographic (EMG) activity of the agonist muscle in 8 patients with Parkinson's disease (PD). Patients were examined during STN-DBS (ON), and 30 minutes after switching off both stimulators (OFF). They were asked to make a ballistic movement in paradigms of simple reaction time (SRT) and choice reaction time (CRT) tasks. Onset of movement (MOVonset) was measured as the latency of the initial displacement from baseline of the signal from an accelerometer attached to the dorsum of the hand. In the associated EMG activity, recorded from wrist extensor muscles, we measured onset latency (EMGonset), size of the first EMG burst (EMGsize), and number of EMG bursts (EMGbursts) counted between EMGonset and task execution. MOVonset and EMGonset were significantly shorter in ON than in OFF conditions in CRT. EMGsize was larger, EMGbursts were reduced, and peak of the acceleration profile was larger in ON compared with OFF conditions in both SRT and CRT. Our results indicate that STN-DBS induces a significant improvement in motor performance of reaction time tasks in PD patients. Such improvement is associated with a change in features of the EMG activity suggesting an increase in the excitability of the motor pathways engaged in ballistic movements.

Aged↗

Subthalamic nucleus stimulation for advanced Parkinson's disease: how to find a far medial STN.

In a patient with advanced Parkinson's disease, an anatomically deviant far medial subthalamic nucleus (STN) posed problems in the placement of DBS electrodes for chronic high frequency (HF) stimulation despite the use of multimodal targeting with 1) statistical atlas data, 2) T (2)-weighted (T (2)W) magnetic resonance imaging (MRI), 3) microelectrode recording, and 4) clinical testing with macro stimulation. Diagnostic T (2)W MRI suggested that the patient's STN was in a typical location and seemed to confirm the statistical atlas-based planning. Intraoperatively, cell activity recording (MER) with five parallel electrodes could not reveal any STN typical activity profile and electrical stimulation was not able to disclose a medial or lateral displacement of the electrodes. The operation was discontinued and postoperative stereotactic CT confirmed that the correct target area had been approached during the operation. Postoperative T (2)W MRI now disclosed a left STN which was 2 mm medial of the initial target and lead to a further medial target definition and finally to a successful DBS placement. In conclusion, finding a deep seated DBS target like the STN can be difficult in cases with an extremely deviant anatomy even if reiterative sophisticated multimodal planning is used. In the presented case we applied the integrated information from intraoperative MER, macrostimulation and postoperative imaging work-up and were able to complete DBS implantation successfully.

Brain Mapping↗

Does subthalamic nucleus stimulation affect the frontal limbic areas? A single-photon emission computed tomography study using a manual anatomical segmentation method.

Among the basal ganglia nuclei, the subthalamic nucleus (STN) is considered to play a major role in output modulation. The STN represents a relay of the motor cortico-basal ganglia-thalamo-cortical circuit and has become the standard surgical target for treating Parkinson's patients with long-term motor fluctuations and dyskinesia. But chronic bilateral stimulation of the STN produces cognitive effects. According to animal and clinical studies, the STN also appears to have direct or indirect connections with the frontal associative and limbic areas. This prospective study was conducted to analyse regional cerebral blood flow changes in single-photon emission computed tomography imaging of six Parkinson's patients before and after STN stimulation. We particularly focused on the dorsolateral prefrontal cortex and the frontal limbic areas using a manual anatomical MRI segmentation method. We defined nine regions of interest, segmenting each MR slice to quantify the regional cerebral blood flow on pre- and postoperative SPECT images. We normalised the region-of-interest-based measurements to the entire brain volume. The patients showed increased activation during STN stimulation in the dorsolateral prefrontal cortex bilaterally and no change in the anterior cingulate and orbito-frontal cortices. In our study, STN stimulation induced activation of premotor and associative frontal areas. Further studies are needed to underline involvement of the STN with the so-called limbic system.

Antiparkinson Agents↗

Does increased excitatory drive from the subthalamic nucleus contribute to dopaminergic neuronal death in Parkinson's disease?

Excitotoxicity has been suggested to play a pivotal role in the pathogenesis of Parkinson disease (PD). As subthalamic nucleus (STN) neurons express glutamate and are overactivated in parkinsonism, it seems that in PD dopaminergic (DA) neurons are under the influence of abnormally high levels of glutamate and consequently might be more vulnerable to neurodegeneration. To determine the contribution of the overactivated STN-SN pathway to the progression of PD, we studied the effect of prior unilateral STN lesion on the toxicity induced by subsequent administration of 1-methyl-4-phenyl-1,2,3,6, tetrahydropyridine (MPTP) to non-human primates. In animals from group 1, kainic-induced lesion of the STN was performed prior to the administration of MPTP whereas in animals from group 2, STN lesion was caused after animals had been chronically treated with MPTP. The lesion of the STN elicited a contralateral hemiballism in animals from group 1, and they developed an asymmetrical parkinsonism after being exposed to MPTP. The STN lesion produced an improvement in the contralateral parkinsonism and mild choreic movements in animals from group 2. Cell counting of tyrosine hydroxylase immunoreactive (TH-ir) cells was performed by stereology and showed a similar loss of TH-ir cells (approximately 85%) in the ipsilateral and contralateral SN to the lesioned STN. These data indicate that the surgical removal of the excitatory drive from the STN to SN neurons does not protect dopaminergic neurons against a chronic and extended toxic effect of MPTP and do not support the assumption that STN blockade might delay the progression of PD.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

Direct effect of subthalamic nucleus stimulation on levodopa-induced peak-dose dyskinesia in patients with Parkinson's disease.

We examined the direct effect of deep brain stimulation of the subthalamic nucleus (STN-DBS) on levodopa-induced peak-dose dyskinesia in 45 patients with Parkinson's disease (PD) without reducing the levodopa dosage during the early period after surgery. In 8 patients (18%), the dyskinesia was quickly attenuated by bipolar stimulation in an experimental trial (5 min) with the contacts placed within the area above the STN. In contrast, bipolar stimulation using contacts placed within the STN itself tended to provoke or exacerbate the dyskinesia, indicating that dyskinesia could be inhibited by stimulation of the areas above the STN rather than the STN itself. In an attempt to control the cardinal symptoms of PD and dyskinesia at the same time, we employed bipolar stimulation with a longer interpolar distance as a therapeutic procedure (2 weeks), using contacts within the STN as a cathode and contacts within the area above the STN as an anode. Bilateral STN-DBS significantly attenuated the dyskinesia as evaluated by the dyskinesia severity rating scale (p < 0.05). In 24 patients (53%), almost complete control of the dyskinesia was observed. The contacts used as an anode in these patients were located more dorsally compared to those of the remaining patients, suggesting again that the dyskinesia was inhibited by stimulation of the areas above the STN rather than the STN itself. In the area above the STN, pallidothalamic, pallidosubthalamic and subthalamopallidal fibers are densely distributed. It appears that stimulation of these fibers may cause effects similar to thalamic or pallidal DBS and therefore inhibit peak-dose dyskinesia. Bipolar STN-DBS with contacts placed within the area above the STN as an anode appears to represent a useful option for controlling both the cardinal symptoms of PD and peak-dose dyskinesia at the same time.

Antiparkinson Agents↗

Effect of chronic deep brain stimulation of the subthalamic nucleus for frontal lobe epilepsy: subtraction SPECT analysis.

OBJECTIVES: Experimental data and case reports of patients with intractable epilepsy treated with deep brain stimulation (DBS) of the subthalamic nucleus (STN) suggest a considerable anticonvulsant effect. However, no satisfactory mechanisms of action have yet been elucidated. We investigated the putative therapeutic mechanisms of DBS from cerebral perfusion changes as measured by subtracting the SPECT image of the pre-DBS period from that of the chronic post-DBS state. METHODS: Two patients who had previous resective surgery on their right frontal cortices with or without anterior callosotomy were selected for DBS of the STN. Both of them showed frequent bilateral asymmetric tonic seizures (left > right) with rare drop attacks, and 1 patient's seizure frequency was more than 15/month during the pre-DBS period. They had both taken more than four antiepileptic agents for more than 10 years. After video-EEG monitoring, the irritative zones of the brain were delineated. The regional cerebral blood flow (rCBF) changes between the two SPECT images (pre-DBS and post-DBS after at least 6 months) were analyzed by SPECT subtraction with the volumetric MRI coregistration method using Analyze 5.0 software. RESULTS: After chronic STN DBS (18 months, case 1; 6 months, case 2), both patients experienced markedly reduced seizure frequencies (86.7% reduction in patient 1, 88.6% in patient 2). In patient 1, the increased rCBF was observed in the right frontal areas (dorsolateral and inferior frontal area), which corresponded to the irritative zones as confirmed by previous EEG recording. Unexpectedly, there was definite hyperperfusion in the right superior and inferior temporal areas as well as rCBF increase in the right superior frontal area (SMA) in patient 2. CONCLUSIONS: We demonstrated that the cerebral perfusion increase in the irritative zones of epilepsy patients is associated with favorable seizure reduction after STN DBS in 2 cases of frontal lobe epilepsy. Although the exact mechanism remains unknown, our findings suggest that the perfusion changes after STN DBS in frontal lobe epilepsy patients are quite different from those in subjects with Parkinson's disease. Our preliminary data suggest the clinical relevance of subtraction SPECT imaging in assessing the postprocedural outcome as well as the characteristics of SPECT perfusion patterns in other epilepsy syndromes.

Adult↗

Circling behaviour induced by activation of GABAA receptors in the subthalamic nucleus.

The behavioural effect of drugs acting on GABAA receptors in the subthalamic region and the entopeduncular nucleus was studied in freely moving cats. Microinjections of muscimol into the zona incerta-Forel's fields produced tilt of the head to the injected site, while injections of bicuculline or picrotoxin produced the same effect but to the opposite side. Microinjections of muscimol into the subthalamic nucleus elicited circling behaviour to the contralateral side, while bicuculline and picrotoxin produced ipsilateral turning. However, when high doses of the antagonists were injected, contralateral circling was observed. Activation or blockade of GABAA receptors into the entopeduncular nucleus was ineffective. These results imply that GABAergic mechanisms in the subthalamic nucleus and the zona incerta-fields of Forel are involved in circling behaviour and vertical head movements, respectively.

Animals↗

Deep brain stimulation of the subthalamic nucleus reduces antiparkinsonian medication costs.

This study reports a retrospective analysis of 16 patients to determine changes in medication costs associated with deep brain stimulation of the bilateral subthalamic nucleus (DBS B-STN). Antiparkinsonian medication (APMED) costs were evaluated pre- and post-operatively at 1 and 2 years, based on prescribed dosages. After treatment with DBS, patients experienced a 32% reduction in APMED costs after 1 year and a 39% reduction after 2 years. Hypothetical projections of total potential savings are presented, accounting for increasingly complex medication regimens and medication cost inflation. DBS patients may experience a significant long-term reduction in the cost of their pharmacologic treatment.

Amantadine↗

Effects of subthalamic nucleus deep brain stimulation and levodopa on energy production rate and substrate oxidation in Parkinson's disease.

Patients with Parkinson's disease (PD) often lose weight, but after subthalamic nucleus deep brain stimulation (STN-DBS), they gain weight. We compared daily energy intake (DEI), resting energy expenditure (REE) and substrate oxidation rates (measured by indirect calorimetry) in nineteen STN-DBS-treated patients (Group S), thirteen others on pharmacologic treatment by levodopa (Group L) and eight control subjects. We also determined the acute effects of STN-DBS and levodopa on REE and substrate oxidation rates. STN-DBS treated patients gained 9.7 (SEM 7.1) kg after surgery, whereas patients on pharmacologic treatment lost 3.8 (SEM 10.0) kg since diagnosis. In STN-DBS-treated patients, REE (-16.5 %; P<0.001), lipid oxidation (-27 %; P<0.05) and protein oxidation (-46 %; P<0.05) were decreased, whereas glucose oxidation was elevated (+81 %; P<0.05) as compared to patients on pharmacologic treatment. Levodopa acutely reduced REE (-8.3 %; P<0.05) and glucose oxidation (-37 %; P<0.01) with a slight hyperglycaemic effect (after levodopa challenge: 5.6 (SEM 0.8) v. before levodopa challenge: 5.3 (SEM 0.6) mmol/l; P<0.01). Switching 'on' STN-DBS acutely reduced REE (-17.5 %; P<0.01) and lipid oxidation (-24 %; P<0.001) 30 min after starting stimulation. Fasting glycaemia was slightly but significantly reduced (5.4 (SEM 1.4) v. 5.5 (SEM 1.3) mmol/l; P<0.01). After STN-DBS, the normalization of REE and the reduction in lipid and protein oxidation contribute to the restoration of weight. As levodopa decreases glucose oxidation, the reduction in daily dose of levodopa in STN-DBS-treated patients helps prevent the effect of weight gain on glycaemia.

Antiparkinson Agents↗

Globus pallidus neurons dynamically regulate the activity pattern of subthalamic nucleus neurons through the frequency-dependent activation of postsynaptic GABAA and GABAB receptors.

Reciprocally connected GABAergic neurons of the globus pallidus (GP) and glutamatergic neurons of the subthalamic nucleus (STN) are a putative generator of pathological rhythmic burst firing in Parkinson's disease (PD). Burst firing of STN neurons may be driven by rebound depolarization after barrages of GABA(A) receptor (GABA(A)R)-mediated IPSPs arising from pallidal fibers. To determine the conditions under which pallidosubthalamic transmission activates these and other postsynaptic GABARs, a parasagittal mouse brain slice preparation was developed in which pallidosubthalamic connections were preserved. Intact connectivity was first confirmed through the injection of a neuronal tracer into the GP. Voltage-clamp and gramicidin-based perforated-patch current-clamp recordings were then used to study the relative influences of GABA(A)R- and GABA(B)R-mediated pallidosubthalamic transmission on STN neurons. Spontaneous phasic, but not tonic, activation of postsynaptic GABA(A)Rs reduced the frequency and disrupted the rhythmicity of autonomous firing in STN neurons. However, postsynaptic GABA(B)Rs were only sufficiently activated to impact STN firing when pallidosubthalamic transmission was elevated or pallidal fibers were synchronously activated by electrical stimulation. In a subset of neurons, rebound burst depolarizations followed high-frequency, synchronous stimulation of pallidosubthalamic fibers. Although GABA(B)R-mediated hyperpolarization was itself sufficient to generate rebound bursts, coincident activation of postsynaptic GABA(A)Rs produced longer and more intense burst firing. These findings elucidate a novel route through which burst activity can be generated in the STN, and suggest that GABARs on STN neurons could act in a synergistic manner to generate abnormal burst activity in PD.

2-Amino-5-phosphonovalerate↗

Comparison of pallidal and subthalamic nucleus deep brain stimulation for advanced Parkinson's disease: results of a randomized, blinded pilot study.

OBJECTIVE: Deep brain stimulation (DBS) of the globus pallidus internus (GPi) and subthalamic nucleus (STN) has been reported to be effective in alleviating the symptoms of advanced Parkinson's disease (PD). Although recent studies suggest that STN stimulation may be superior to GPi stimulation, a randomized, blinded comparison has not been reported. The present study was designed to provide a preliminary comparison of the safety and efficacy of DBS at either site. METHODS: Ten patients with idiopathic PD, L-dopa-induced dyskinesia, and response fluctuations were randomized to implantation of bilateral GPi or STN stimulators. Neurological condition was assessed preoperatively with patients on and off L-dopa and on DBS at 10 days and 3, 6, and 12 months after implantation. Patients and evaluating clinicians were blinded to stimulation site throughout the study period. Complete follow-up data were analyzed for four GPi patients and five STN patients. RESULTS: When off-L-dopa, both GPi and STN groups demonstrated a similar response, with approximately 40% improvement in Unified PD Rating Scale motor scores after 12 months of DBS. Rigidity, tremor, and bradykinesia improved in both groups. In combination with L-dopa, Unified PD Rating Scale motor scores were more improved by GPi stimulation than by STN stimulation. On-L-dopa axial symptoms were clinically improved in the GPi but not the STN group. L-Dopa-induced dyskinesia was reduced by DBS at either site, although medication requirement was reduced only in the STN group. There were no serious intraoperative complications among patients in either group. CONCLUSION: Pallidal and STN stimulation appears to be safe and efficacious for the management of advanced PD. A larger study is needed to investigate further the differences in symptom response and the interaction of L-dopa with stimulation at either site.

Adult↗

Bilateral subthalamic nucleus stimulation improves health-related quality of life in Parkinsonian patients.

Parkinson's disease (PD) is a common neurological disorder. Recently, bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become an option in the treatment of severe PD. We measured the health-related quality of life (HRQoL) of 27 parkinsonian patients, who underwent a bilateral STN-operation. The instruments used for the evaluation of the HRQoL were the Parkinson's Disease Questionnaire (PDQ-39) and the Finnish version of the Nottingham Health Profile (NHP). We found that the quality of life significantly improved when measured with both HRQoL scales. Clinical improvement and improvement in HRQoL were positively correlated.

Aged↗

Placebo-responsive Parkinson patients show decreased activity in single neurons of subthalamic nucleus.

Placebo administration is known to affect the brain both in pain and in Parkinson disease. Here we show that placebo treatment caused reduced activity in single neurons in the subthalamic nucleus of placebo-responsive Parkinsonian patients. These changes in activity were tightly correlated with clinical improvement; no decrease in activity occurred when the clinical placebo response was absent.

Action Potentials↗

Unilateral subthalamic nucleus lesioning: a safe and effective treatment for Parkinson's disease.

The present study, the largest in the literature, was performed to assess the effectiveness and safety of unilateral subthalamic nucleus (STN) lesioning for Parkinson's disease (PD). From August 1999 to September 2000, 21 consecutive patients evaluated pre- and postoperatively by a single examiner were operated. Levodopa intake and dyskinesia, Hoehn & Yahr, Schwab & England and UPDRS motor scores were recorded. Stereotactic CT and MRI and the effects of macrostimulation were used to determine STN coordinates. A single radiofrequency lesion was made (60-75 degrees C/60"). Concomitant ipsilateral Vim/VOp lesions were made in 8 patients. Using a new technique, we were able to determine the territory of STN involved by the surgical lesion. The Wilcoxon and Mann-Whitney statistical tests were applied to evaluate the surgical results. All recorded parameters showed stable improvement after a mean follow up of 13.5 months. Recurrence occurred in two patients. Contralateral tremor arrest and decrease of rigidity and bradykinesia should be regarded as STN hallmarks to stimulation. Hyperintense lesions in the early-phase MRI seem to be a poor prognostic factor. Lateral territory lesioning correlates with better results. There was no significant difference between the cohorts with and without a Vim/VOp lesion. Dyskinesias happened in two patients (promptly abolished by a Vim/VOp lesion). Other complications were transient and/or rare. In conclusion, STN lesioning is a safe and very effective procedure to treat PD and probably an underutilized operation for those who can not afford the costs of DBS.

Adult↗

Changes in the firing pattern of globus pallidus neurons after the degeneration of nigrostriatal pathway are mediated by the subthalamic nucleus in the rat.

Changes in the neuronal activity of globus pallidus (GP) have been shown in animal models of parkinsonism. In order to study the implication of the subthalamic nucleus (STN) in these changes, the effects of STN lesions alone or in combination with 6-hydroxydopamine (6-OHDA) -induced damage to the substantia nigra compacta (SNc) were examined in rats using electrophysiological recordings of GP cells. In normal rats, the firing rate was 22.1+/-1.4 spikes/s. The pattern was regular in 45%, irregular in 49% and bursty in 6% of the cases. In rats with STN lesions, the firing rate of GP units (20.15+/-1.25 spikes/s) did not differ from that of normal rats and only regular (46%) and irregular (54%) cells were found; a bursty pattern was not observed. 6-OHDA lesions of the SNc induced no change in the firing rate of GP neurons (21.5+/-1.4 spikes/s, P>0.05) but a significant decrease in the percentage of regular cells (27%, P<0.001), a significant increase in burst cells (21%, P<0.001) with no change in the percentage of irregular units (52%) were observed. In rats with combined SNc and STN lesions, the firing pattern did not change from that of normal rats. The present results show that STN lesions induced the disappearance of bursts in normal rats and normalization of firing pattern in the GP units of rats with 6-OHDA lesions suggesting that the STN plays an important role in the modulation of the pattern of activity of GP neurons which may account for the therapeutic effect of STN lesions in Parkinson's disease.

Animals↗