Structural-Functional Correlates of Response to Pedunculopontine Stimulation in a Randomized Clinical Trial for Axial Symptoms of Parkinson's Disease

BACKGROUND

Axial symptoms of Parkinson's disease (PD) can be debilitating and are often refractory to conventional therapies such as dopamine replacement therapy and deep brain stimulation (DBS) of the subthalamic nuclei (STN).

OBJECTIVE

Evaluate the efficacy of bilateral DBS of the pedunculopontine nucleus area (PPNa) and investigate structural and physiological correlates of clinical response.

METHODS

A randomized, double-blind, cross-over clinical trial was employed to evaluate the efficacy of bilateral PPNa-DBS on axial symptoms. Lead positions and neuronal activity were evaluated with respect to clinical response. Connectomic cortical activation profiles were generated based on the volumes of tissue activated.

RESULTS

PPNa-DBS modestly improved (p = 0.057) axial symptoms in the medication-off condition, with greatest positive effects on gait symptoms (p = 0.027). Electrode placements towards the anterior commissure (ρ= 0.912; p = 0.011) or foramen caecum (ρ= 0.853; p = 0.031), near the 50% mark of the ponto-mesencephalic junction, yielded better therapeutic responses. Recording trajectories of patients with better therapeutic responses (i.e., more anterior electrode placements) had neurons with lower firing-rates (p = 0.003) and higher burst indexes (p = 0.007). Structural connectomic profiles implicated activation of fibers of the posterior parietal lobule which is involved in orienting behavior and locomotion.

CONCLUSION

Bilateral PPNa-DBS influenced gait symptoms in patients with PD. Anatomical and physiological information may aid in localization of a favorable stimulation target.

White matter integrity and pro-inflammatory cytokines as predictors of antidepressant response in MDD

Introduction

Major depressive disorder (MDD) often involves immune dysregulation with high peripheral levels of pro-inflammatory cytokines that might have an impact on the clinical course and treatment response. Moreover, MDD patients show brain volume changes and white matter (WM) alterations that are already existing in the early stage of illness.

Objectives

The aim of the present review is to elucidate the association between inflammation and WM integrity and its impact on the pathophysiology and progression of MDD as well as the role of possible novel biomarkers of treatment response to improve MDD prevention and treatment strategies.

Methods

We conducted an electronic literature search of PubMed on studies that examined the role of inflammation in depression and that focused on WM integrity and pro-inflammatory cytokines as predictors of antidepressant response.

Results

There is evidence for central effects of peripheral inflammation which could activate microglia which, in turn, might trigger a cascade of inflammatory processes leading to neurotransmitter imbalances. Numerous studies indicated that both altered levels of peripheral inflammatory markers, particularly TNF-α, IL-6, and CRP as well as WM integrity might predict antidepressant treatment outcome.

Conclusions

Despite mounting evidence on the impact of the immune system on WM microstructure, no study has yet addressed the interaction between the two factors in influencing antidepressant response. There is a lack of reproducible biomarkers predicting treatment response on an individual basis. The availability of such biomarkers would enable more efficient and personalized treatments with a faster treatment response and better prevention of treatment resistance.

Disclosure

No significant relationships.

Posterior fossa syndrome with a large inflammatory ponto-mesencephalic lesion

Demonstration of a posterior fossa syndrome (PFS) in a 32-year-old male patient with clinically isolated syndrome which subsequently developed into relapsing-remitting Multiple Sclerosis. The patient suffered from double vision, coordination problems including unsteady gait and atactic dysarthria, concentration difficulties, as well as adynamia and impaired decision making. The patient clinically presented a cerebellar and dysexecutive syndrome. Cerebral magnetic resonance imaging (MRI) revealed a contrast enhancing ponto-mesencephalic lesion with a volume of 4.8cm³. Neuropsychological tests showed pronounced executive dysfunctions, reduced visuoconstructive skills, attentional deficits, echolalia, and non-fluent speech production. After cortisone and plasmapheresis, the cerebellar syndrome improved but manual fine motor skills and executive dysfunctions persisted. After three months, symptoms remitted except for a slight gait imbalance. After six months, neuropsychological tests were normal except for a moderate attention deficit. MRI revealed a clear regression of the ponto-mesencephalic lesion to a volume of 2.4cm³ without contrast enhancement. This case report intends to provide an overview of the symptomatology and etiology of PFS and offers new insights into its pathomechanism demonstrating a pontine disconnection syndrome caused by a large demyelinating plaque.

The subthalamic nucleus modulates the early phase of probabilistic classification learning

Previous models proposed that the subthalamic nucleus (STN) is critical in the early phase of skill acquisition. We hypothesized that subthalamic deep brain stimulation modulates the learning curve in early classification learning. Thirteen idiopathic Parkinson's disease patients (iPD) with subthalamic deep brain stimulation (STN-DBS), 9 medically treated iPD, and 21 age-matched healthy controls were tested with a probabilistic classification task. STN-DBS patients were tested with stimulation OFF and ON, and medically treated patients with medication OFF and ON, respectively. Performance and reaction time were analyzed on the first 100 consecutive trials as early learning phase. Moreover, data were separated for low and high-probability patterns, and more differentiated strategy analyses were used. The major finding was a significant modulation of the learning curve in DBS patients with stimulation ON: although overall learning was similar to healthy controls, only the stimulation ON group showed a transient significant performance dip from trials '41-60' that rapidly recovered. Further analysis indicated that this might be paralleled by a modulation of the learning strategy, particularly on the high-probability patterns. The reaction time was unchanged during the dip. Our study supports that the STN serves as a relay in early classification learning and directs attention toward unacquainted content. The STN might play a role in balancing the short-term success against strategy optimization for improved long-term outcome.

Nigral stimulation for resistant axial motor impairment in Parkinson's disease? A randomized controlled trial

Gait and balance disturbances typically emerge in advanced Parkinson’s disease with generally limited response to dopaminergic medication and subthalamic nucleus deep brain stimulation. Therefore, advanced programming with interleaved pulses was put forward to introduce concomittant nigral stimulation on caudal contacts of a subthalamic lead. Here, we hypothesized that the combined stimulation of subthalamic nucleus and substantia nigra pars reticulata improves axial symptoms compared with standard subthalamic nucleus stimulation. Twelve patients were enrolled in this 2 × 2 cross-over double-blind randomized controlled clinical trial and both the safety and efficacy of combined subthalamic nucleus and substantia nigra pars reticulata stimulation were evaluated compared with standard subthalamic nucleus stimulation. The primary outcome measure was the change of a broad-scaled cumulative axial Unified Parkinson’s Disease Rating Scale score (Scale II items 13–15, Scale III items 27–31) at ‘3-week follow-up’. Secondary outcome measures specifically addressed freezing of gait, balance, quality of life, non-motor symptoms and neuropsychiatric symptoms. For the primary outcome measure no statistically significant improvement was observed for combined subthalamic nucleus and substantia nigra pars reticulata stimulation at the ‘3-week follow-up’. The secondary endpoints, however, revealed that the combined stimulation of subthalamic nucleus and substantia nigra pars reticulata might specifically improve freezing of gait, whereas balance impairment remained unchanged. The combined stimulation of subthalamic nucleus and substantia nigra pars reticulata was safe, and of note, no clinically relevant neuropsychiatric adverse effect was observed. Patients treated with subthalamic nucleus and substantia nigra pars reticulata stimulation revealed no ‘global’ effect on axial motor domains. However, this study opens the perspective that concomittant stimulation of the substantia nigra pars reticulata possibly improves otherwise resistant freezing of gait and, therefore, highly warrants a subsequent phase III randomized controlled trial.

Deep-brain-stimulation does not impair deglutition in Parkinson's disease

OBJECTIVE

A large proportion of patients with Parkinson's disease develop dysphagia during the course of the disease. Dysphagia in Parkinson's disease affects different phases of deglutition, has a strong impact on quality of life and may cause severe complications, i.e., aspirational pneumonia. So far, little is known on how deep-brain-stimulation of the subthalamic nucleus influences deglutition in PD.

METHODS

Videofluoroscopic swallowing studies on 18 patients with Parkinson's disease, which had been performed preoperatively, and postoperatively with deep-brain-stimulation-on and deep-brain-stimulation-off, were analyzed retrospectively. The patients were examined in each condition with three consistencies (viscous, fluid and solid). The 'New Zealand index for multidisciplinary evaluation of swallowing (NZIMES) Subscale One' for qualitative and 'Logemann-MBS-Parameters' for quantitative evaluation were assessed.

RESULTS

Preoperatively, none of the patients presented with clinically relevant signs of dysphagia. While postoperatively, the mean daily levodopa equivalent dosage was reduced by 50% and deep-brain-stimulation led to a 50% improvement in motor symptoms measured by the UPDRS III, no clinically relevant influence of deep-brain-stimulation-on swallowing was observed using qualitative parameters (NZIMES). However quantitative parameters (Logemann scale) found significant changes of pharyngeal parameters with deep-brain-stimulation-on as compared to preoperative condition and deep-brain-stimulation-off mostly with fluid consistency.

CONCLUSION

In Parkinson patients without dysphagia deep-brain-stimulation of the subthalamic nucleus modulates the pharyngeal deglutition phase but has no clinically relevant influence on deglutition. Further studies are needed to test if deep-brain-stimulation is a therapeutic option for patients with swallowing disorders.

Subthalamic nucleus stimulation restores the efferent cortical drive to muscle in parallel to functional motor improvement

Pathological synchronization in large-scale motor networks constitutes a pathophysiological hallmark of Parkinson's disease (PD). Corticomuscular synchronization in PD is pronounced in lower frequency bands (< 10 Hz), whereas efficient cortical motor integration in healthy persons is driven in the beta frequency range. Electroencephalogram and electromyogram recordings at rest and during an isometric precision grip task were performed in four perioperative sessions in 10 patients with PD undergoing subthalamic nucleus deep-brain stimulation: (i) 1 day before (D0); (ii) 1 day after (D1); (iii) 8 days after implantation of macroelectrodes with stimulation off (D8StimOff); and (iv) on (D8StimOn). Analyses of coherence and phase delays were performed in order to challenge the effects of microlesion and stimulation on corticomuscular coherence (CMC). Additionally, local field potentials recorded from the subthalamic nucleus on D1 allowed comprehensive mapping of motor-related synchronization in subthalamocortical and cerebromuscular networks. Motor performance improved at D8StimOn compared with D0 and D8StimOff paralleled by a reduction of muscular activity and CMC in the theta band (3.9-7.8 Hz) and by an increase of CMC in the low-beta band (13.7-19.5 Hz). Efferent motor cortical drives to muscle presented mainly below 10 Hz on D8StimOff that were suppressed on D8StimOn and occurred on higher frequencies from 13 to 45 Hz. On D1, coherence of the high-beta band (20.5-30.2 Hz) increased during movement compared with rest in subthalamomuscular and corticomuscular projections, whereas it was attenuated in subcorticocortical projections. The present findings lend further support to the concept of pathological network synchronization in PD that is beneficially modulated by stimulation.

Combined STN/SNr-DBS for the treatment of refractory gait disturbances in Parkinson's disease: study protocol for a randomized controlled trial

BACKGROUND

Severe gait disturbances in idiopathic Parkinson's disease (PD) are observed in up to 80% of all patients in advanced disease stages with important impact on quality of life. There is an unmet need for further symptomatic therapeutic strategies, particularly as gait disturbances generally respond unfavourably to dopaminergic medication and conventional deep brain stimulation of the subthalamic nucleus in advanced disease stages. Recent pathophysiological research pointed to nigro-pontine networks entrained to locomotor integration. Stimulation of the pedunculopontine nucleus is currently under investigation, however, hitherto remains controversial. The substantia nigra pars reticulata (SNr)--entrained into integrative locomotor networks--is pathologically overactive in PD. High-frequent stimulation of the substantia nigra pars reticulata preferentially modulated axial symptoms and therefore is suggested as a novel therapeutic candidate target for neuromodulation of refractory gait disturbances in PD.

METHODS

12 patients with idiopathic Parkinson's disease and refractory gait disturbances under best individual subthalamic nucleus stimulation and dopaminergic medication will be enroled into this double-blind 2 × 2 cross-over clinical trial. The treatment consists of two different stimulation settings using (i) conventional stimulation of the subthalamic nucleus [STNmono] and (ii) combined stimulation of distant electrode contacts located in the subthalamic nucleus and caudal border zone of STN and substantia nigra pars reticulata [STN+SNr]. The primary outcome measure is the change of the cumulative 'axial score' (UPDRS II items '13-15' and UPRDS III items '27-31') at three weeks of constant stimulation in either condition. Secondary outcome measures include specific scores on freezing of gait, balance function, quality of life, non-motor symptoms, and neuropsychiatric symptoms. The aim of the present trial is to investigate the efficacy and safety of a three week constant combined stimulation on [STN+SNr] compared to [STNmono]. The results will clarify, whether stimulation on nigral contacts additional to subthalamic stimulation will improve therapeutic response of otherwise refractory gait disturbances in PD.

TRIAL REGISTRATION

The trial was registered with the clinical trials register of http://www.clinicaltrials.gov (NCT01355835).

Central oscillators in a patient with neuropathic tremor: evidence from intraoperative local field potential recordings

Present pathophysiological concepts of neuropathic tremor assume mistimed and defective afferent input resulting in deregulation of cerebello-thalamo-cortical motor networks. Here, we provide direct evidence of central tremor processing in a 76-year-old female who underwent bilateral deep brain stimulation of the ventral intermedial nucleus of the thalamus (Vim-DBS) because of neuropathic tremor associated with IgM paraproteinemia. Electrophysiological recordings of EEG and EMG were performed in three perioperative sessions: (1) preoperatively, (2) intraoperatively, and (3) 4 days after surgery in both rest and postural tremor conditions. Tremor-related synchronization (coherence) between motor cortex (M1) and muscles (M. extensor digitorum, M. flexor digitorum) was assessed, and additional intraoperative local field potential (LFP) recordings from Vim allowed comprehensive coherence mapping in thalamo-cortico-muscular networks. Directionality of information flow was determined by directed transfer function (DTF) and phase analyses. Stimulation effects on tremor and corticomuscular coherence were assessed and the patient was followed for 12 months on clinical outcome measures (Tremor Rating Scale, CADET-Score). Vim-DBS reduced tremor (59%) and improved motor functionality in daily activities (31%, CADET-A) after 12 months. Intraoperative recordings demonstrated significant coherence in the tremor frequency (4 Hz) between M1 and contralateral muscle, Vim and ipsilateral M1, Vim and contralateral muscle, but not between Vim and contralateral M1. Information flow was directed from M1 to Vim and bidirectional between M1 and muscle and between Vim and muscle, respectively. Corticomuscular coherence at tremor frequency was completely suppressed by Vim-DBS. Our case study demonstrates central oscillators underlying neuropathic tremor and implies a strong pathophysiological rationale for Vim-DBS.

Involuntary eyelid closure after STN-DBS: evidence for different pathophysiological entities

OBJECTIVE

Involuntary eyelid closure (IEC) may occur after deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson's disease (PD) and is often categorised as apraxia of lid opening (ALO), albeit the appropriateness of this term is under debate. To gain insight into the hitherto undefined pathophysiology of IEC after STN-DBS, we performed a comprehensive clinical and electrophysiological characterisation of lid function in a total of six PD patients.

METHODS

The study was carried out in six PD patients who developed IEC after STN-DBS. They underwent neurological examination and electromyography recording of activity in the orbicularis oculi muscle (OO) upon varying stimulation patterns. Intraoperative studies were performed in one patient.

RESULTS

Increasing STN-DBS intensity induced IEC in four patients, whereas it improved the condition in two. Needle EMG showed tonic hyperactivity of the OO in STN-DBS induced IEC, while variable patterns of OO activity (irregular and tonic) were seen in patients with STN-DBS-relieved IEC. Intraoperative analysis in one patient showed evidence for IEC being induced by activation of corticobulbar fibres.

CONCLUSIONS

We identified two groups of IEC after STN-DBS based on clinical and EMG patterns: (1) STN-DBS induced IEC associated with tonic OO overactivity and (2) STN-DBS relieved IEC presenting with variable EMG patterns. Our findings provide relevant information on pathophysiology of STN-DBS related IEC and implications for its therapeutic management.

Effective long-term subthalamic stimulation in PARK8 positive Parkinson's disease

Whether patients with genetically defined Parkinson's disease (PD) may be particularly eligible to benefit from deep brain stimulation of the nucleus subthalamicus (STN-DBS) is currently the subject of debate. We report on a patient with advanced PD due to R793M missense mutation in the LRRK2 gene successfully treated by STN-DBS. Disease onset was at age 42 with bradykinesia, rigidity and rest tremor. During the course of the disease he developed severe motor fluctuations, dyskinesias, postural instability with falls, but preserved levodopa responsiveness. At age 60 the patient was treated by bilateral DBS of the STN. At one year after surgery a 66% improvement of the UPDRS motor score in the off-medication state was determined. During the long-term follow-up there was sustained benefit with 56% improvement of motor score after 8 years. Our report adds evidence that patients with LRRK2 monogenetic Parkinsonism are well suited candidates for DBS treatment and may indicate a potential genetic predictor for positive long-term effect of STN-DBS treatment.

Identification of candidate biomarkers of therapeutic response to docetaxel in hormone-refractory prostate cancer by proteomic profiling

11010

Background: Docetaxel (DTX)-based chemotherapy improves symptoms and survival in men with advanced hormone-refractory prostate cancer (HRPC). However, approximately 50% of patients do not respond to DTX but are exposed to significant toxicity without direct benefit. This study aimed to identify novel therapeutic targets and predictive biomarkers of DTX-resistance in HRPC. Methods: Protein profiling using iTRAQ mass spectrometry compared the PC3-Rx and DTX-sensitive PC3 cells and DTX-resistant PC3-Rx developed by DTX dose-escalation. Functional validation experiments were performed using recombinant protein treatment and siRNA knockdown experiments. Plasma/serum samples were collected from 41 men with metastatic HRPC treated with DTX-based chemotherapy (36 with paired samples pre- and post- cycle 1 DTX). Serum/plasma levels of MIC-1 were measured by ELISA. The association between MIC-1 levels, PSA response and overall survival (OS) were assessed by non-parametric tests and Kaplan-Meier survival analysis. Results: The IC50 for DTX in PC3-Rx was 10-fold higher than that in parent PC-3 cells. Protein profiling identified that MIC-1 levels were elevated 2.4 fold and AGR2 decreased 2.4 fold in DTX resistant cells. Knockdown of AGR2 expression in PC3 cells resulted in increased DTX resistance (p=0.03). PC-3 cells treated with recombinant MIC-1 also became resistant to DTX (p=0.001). Conversely, treating PC3-Rx cells with MIC1-siRNA restored sensitivity to DTX (p=0.002). In HRPC patients, pre-treatment MIC-1 levels did not correlate with PSA response to treatment (p=0.6). In contrast, increased serum/plasma levels of MIC-1 after cycle one of chemotherapy were associated with DTX resistance (p=0.006) and shorter overall survival (p=0.002). Conclusions: These results suggest that both AGR2 and MIC-1 play a role in DTX resistance in HRPC. Furthermore, changes in serum/plasma MIC-1 levels are associated with DTX resistance in a correlative human cohort. While a larger study is needed to validate these findings, the data provide evidence that MIC-1 as a potential predictive biomarker and both MIC-1 and AGR2 are potential therapeutic targets in DTX resistance.

No significant financial relationships to disclose.

Effective thalamic deep brain stimulation for neuropathic tremor in a patient with severe demyelinating neuropathy

Postural and action tremor in peripheral neuropathy is characteristic of Roussy-Levy syndrome. A patient with a severe demyelinating neuropathy and disabling neuropathic tremor successfully treated by deep brain stimulation (DBS) is reported. Disease onset was at age 63 years with sensory symptoms and slight action tremor. Within the following 9 years a severe, drug resistant, postural and action tremor developed rendering the patient unable to feed himself. At age 72 years the patient was treated by bilateral DBS of the ventral intermediate thalamic nucleus, with a useful 30% reduction in tremor. The clinical benefit of the stimulation remained stable over a 1 year postoperative observation period.

Pretargeting for the implantation of stimulation electrodes into the subthalamic nucleus: a comparative study of magnetic resonance imaging and ventriculography

OBJECTIVE

The optimal imaging modality for preoperative targeting of the subthalamic nucleus (STN) for high-frequency stimulation is controversially discussed. Commonly used methods were stereotactic magnetic resonance imaging (MRI), stereotactic ventriculography, and fusion between MRI and stereotactic computer tomography. All of these techniques not only have their own advantages but also specific limitations and drawbacks. The purpose of this study was to evaluate the accuracy of the preoperative MRI targeting as compared with ventriculography in terms of both the STN target as well as the internal landmarks.

METHODS

Thirty patients with Parkinson's disease who underwent bilateral surgery for STN-high-frequency stimulation received both stereotactic ventriculography and stereotactic MRI. The theoretical target was determined by each of these two imaging modalities. The final electrode placement was performed after extensive electrophysiological evaluation using microrecording and microstimulation. The real target was assumed to be given by the electrode contact with the best clinical result assessed by the United Parkinson's Disease Rating Scale in the postoperative follow-up. In addition, the coordinates of the two landmarks, anterior commissure and posterior commissure, were determined using both imaging methods.

RESULTS

The mean targeting error was 4.1 +/- 1.7 mm (mean +/- standard deviation) for MRI and 2.4 +/- 1.1 mm for ventriculography (P< 0.0001). The mean target mismatch between the two imaging methods was 2.9 +/- 1.2 mm. The length of the anterior commissure-posterior commissure distance differed significantly (P < 0.0001) between MRI (27.6 +/- 1.6 mm) and ventriculography (25.0 +/- 1.3 mm). The mismatch was mainly induced by an anterior displacement of the anterior commissure by 1.9 +/- 2.2 mm (P < 0.0001) in MRI determination, as compared with ventriculography.

CONCLUSION

Our findings show that the indirect targeting of the STN using coordinates based on radiological landmarks is more accurate than the direct targeting using anatomic visualization of the target structure. Regardless of the imaging procedure, electrophysiological mapping is required for optimal electrode placement, although in 20% of cases, the target determined by MRI falls out of the radius explored by electrophysiology.

Long-term EMG recordings differentiate between parkinsonian and essential tremor

The differential diagnosis of tremor is mainly based on clinical criteria.Nevertheless, these criteria are in some cases not sufficient to differentiate between different tremor forms. Long-term EMG has proven to be a valid and reliable method for the quantification of pathological tremors. The aim of the study was to develop a long-term EMG-based automated analysis procedure that separates parkinsonian tremor from essential tremor. Using longterm EMG tremor was recorded in 45 consecutive patients, 26 with Parkinson's disease (PD) and 19 with essential tremor (ET). Eight tremor parameters were generated automatically. By stepwise backward regression a subset of these criteria was extracted to achieve an automated classification of the tremor by a mathematical model. The obtained model was then tested on a new group of 13 patients in early stages of the disease. Significant differences between groups were found for tremor occurrence, tremor asymmetry, mean tremor frequency and standard deviation of phase of antagonistic muscles. Due to data overlap a classification of the two tremor forms was not possible based on a single tremor parameter. Using logistic regression, a linear formula based on the three parameters tremor occurrence, mean tremor frequency and standard deviation of phase was established and predicted the correct diagnosis in 93% of patients. The validation of the model on the new group of patients in early stages of the tremor disease yielded a correct diagnosis in 100% of cases. We conclude that long-term EMG recording allows a rater-independent classification of parkinsonian versus essential tremor.

Lesion of the pedunculopontine nucleus reverses hyperactivity of the subthalamic nucleus and substantia nigra pars reticulata in a 6-hydroxydopamine rat model

The pedunculopontine nucleus (PPN) and the subthalamic nucleus (STN) are reciprocally connected by excitatory projections. In the 6-hydroxydopamine (6-OHDA) rat model the PPN was found to be hyperactive. Similarly, the STN and the substantia nigra pars reticulata (SNr) showed increased activity in Parkinson's disease (PD) animal models. A lesion of the STN was shown to restore increased activity levels in the SNr of 6-OHDA-treated rats. As the STN and the PPN were reciprocally connected by excitatory projections and both structures were shown to be hyperactive in PD animal models, the present study was performed in order to investigate the changes in neuronal activity of the STN and SNr under urethane anesthesia after unilateral ibotenic acid lesioning of the PPN in animals with previous unilateral 6-OHDA lesions of the substantia nigra pars compacta (SNc). The firing rate of STN neurons significantly increased from 10.3 +/- 0.6 spikes/s (mean +/- SEM) to 17.8 +/- 1.8 spikes/s after SNc lesion and returned to normal levels of 10.8 +/- 0.7 spikes/s after additional lesion of the PPN. Similarly, the firing rate of SNr neurons significantly increased from 19.0 +/- 1.1 to 25.9 +/- 1.4 spikes/s after SNc lesion, the hyperactivity being reversed after additional PPN lesion to 16.8 +/- 1.2 spikes/s. The reversal of STN and SNr hyperactivity of 6-OHDA-treated rats by additional PPN lesion suggests an important modulatory influence of the PPN on STN activity. Moreover, these findings could indicate a new therapeutic strategy in PD by interventional modulation of the PPN.

Pretargeting For The Implantation Of Stimulation Electrodes Into The Subthalamic Nucleus:A Comparative Study Of Magnetic Resonance Imaging And Ventriculography

OBJECTIVE:

The optimal imaging modality for preoperative targeting of the subthalamic nucleus (STN) for high-frequency stimulation is controversially discussed. Commonly used methods were stereotactic magnetic resonance imaging (MRI), stereotactic ventriculography, and fusion between MRI and stereotactic computer tomography. All of these techniques not only have their own advantages but also specific limitations and drawbacks. The purpose of this study was to evaluate the accuracy of the preoperative MRI targeting as compared with ventriculography in terms of both the STN target as well as the internal landmarks.

METHODS:

Thirty patients with Parkinson's disease who underwent bilateral surgery for STN-high-frequency stimulation received both stereotactic ventriculography and stereotactic MRI. The theoretical target was determined by each of these two imaging modalities. The final electrode placement was performed after extensive electrophysiological evaluation using microrecording and microstimulation. The real target was assumed to be given by the electrode contact with the best clinical result assessed by the United Parkinson's Disease Rating Scale in the postoperative follow-up. In addition, the coordinates of the two landmarks, anterior commissure and posterior commissure, were determined using both imaging methods.

RESULTS:

The mean targeting error was 4.1 ± 1.7 mm (mean ± standard deviation) for MRI and 2.4 ± 1.1 mm for ventriculography (P &lt; 0.0001). The mean target mismatch between the two imaging methods was 2.9 ± 1.2 mm. The length of the anterior commissure-posterior commissure distance differed significantly (P &lt; 0.0001) between MRI (27.6 ± 1.6 mm) and ventriculography (25.0 ± 1.3 mm). The mismatch was mainly induced by an anterior diplacement of the anterior commissure by 1.9 ± 2.2 mm (P &lt; 0.0001) in MRI determination, as compared with ventriculography.

CONCLUSION:

Our findings show that the indirect targeting of the STN using coordinates based on radiological landmarks is more accurate than the direct targeting using anatomic visualization of the target structure. Regardless of the imaging procedure, electrophysiological mapping is required for optimal electrode placement, although in 20% of cases, the target determined by MRI falls out of the radius explored by electrophysiology.

On the weight-bearing function of the medial coronoid process in dogs

The shape of and proportions between the surface areas of the medial coronoid process (MCP) and the fovea of the radial head were determined in 88 juvenile dogs and 146 adult dogs grouped as giant, large, mid-sized, chondrodystrophic, or small dogs. Thereby, the longitudinal (length) and transverse (width) extension of the MCP and fovea of the radial head have been measured. Original values were used to describe changes of the parameters attributed to growth. Normalized values (i.e. values expected in case of a width of the fovea of the radial head of 20 mm) were used to determine potential differences between constitutional types. All original values increased during growth (P < 0.05) except for the width and length of the MCP in chondrodystrophic and small breeds. Normalized values revealed a proportional decrease in width and length of the MCP during growth (P < 0.05) compared with the radial head. In adults, the normalized MCP was widest in giant dogs followed by large, mid-sized, small, and chondrodystrophic breeds. The MCP was also longest in giant dogs but shortest in large and chondrodystrophic dogs with those of large dogs being significantly (P < 0.05) shorter than those in giant, mid-sized and small dogs. Present results suggest that a deficiency in length-growth of the MCP--which has been present especially in large dogs--results in smaller humeral contact areas and decreased weight-bearing capacity of the MCP. Because loading forces acting on the MCP increase with body weight, the condition noted in large dogs might increase the risk of fragmentation of the MCP in these.

Unilateral lesion of the pedunculopontine nucleus induces hyperactivity in the subthalamic nucleus and substantia nigra in the rat

Recent data suggest a role for the pedunculopontine nucleus (PPN) in the pathophysiology of Parkinson's disease. Although there is anatomical evidence that the PPN and the basal ganglia are reciprocally connected, the functional importance of these connections is poorly understood. Lesioning of the PPN was shown to induce akinesia in primates, whereas in the 6-hydroxydopamine rat model the PPN was found to be hyperactive. As both nigrostriatal dopamine depletion and lesioning of the PPN were shown to induce akinesia and parkinsonism, the present study was performed in order to investigate the changes in neuronal activity of the subthalamic nucleus (STN) and the substantia nigra pars reticulata (SNr) after unilateral ibotenic acid lesioning of the PPN and after unilateral 6-hydroxydopamine lesioning of the substantia nigra pars compacta (SNc). The firing rate of STN neurones significantly increased from 10.2 +/- 6.2 (mean +/- SD) to 14.6 +/- 11.7 spikes/s after lesion of the PPN and to 18.6 +/- 14.5 spikes/s after lesion of the SNc. The activity of the SNr significantly increased from 19.6 +/- 10.5 to 28.7 +/- 13.4 spikes/s after PPN lesioning and to 23.5 +/- 10.8 spikes/s after SNc lesioning. Furthermore, PPN lesion decreased the number of spontaneously firing dopaminergic SNc cells, while having no effect on their firing rate. The results of our study show that lesion of the PPN leads to hyperactivity of the STN and SNr, similar to the changes induced by lesion of the SNc. Moreover, the decreased activity of SNc cells observed after PPN lesion might be at the origin of activity changes in the STN and SNr.

Postnatal Modelling of the Humeroantebrachial Contact Areas of Radius and Ulna in Dogs

Necropsy dogs (n = 234) ranging in age between 2 days and 17 years were examined to characterize the cross-sectional shape of the humeroantebrachial contact area of the radius and ulna on radioulnar scans of giant, large, mid-sized, small, and chondrodystrophic breeds. During growth, the contact areas became more circular in shape in all breeds, those in small dogs remained most elliptic. Smallest normalized heights (distance between the tip of the anconeal process and the most proximal aspect of the cranial margin of the radial head = RUH, distance between the tip of the anconeal process and the cranial tip of the medial coronoid process = UH) and depths (distance determined in a right angle to RUH = RUD, distance determined in a right angle to UH = UD) were noted in large and giant breeds with no significant difference between these. In juveniles, a decrease in UD was correlated with a decrease in UH in all breeds as was a decrease in RUD correlated with a decrease in RUH, whereas in non-arthrotic adults this condition could only be proven for mid-sized dogs and small breeds but not for giant, large and chondrodystrophic dogs. The average radioulnar and ulnar heights and depths (as seen in non-arthrotic adults) were calculated to be obtained in mid-sized dogs at least 3-4 weeks earlier than in large dogs. Lipping of the cranial margin of the radial head was significantly (P < 0.001) associated with lesion(s) of the articular surface (i.e. erosion of the articular cartilage and subchondral bone and/or fragmentation of the medial coronoid process) and caused additional change in shape of this contact area, which was then even more circular. However, the variables evaluated (RUH, RUD, UH, UD) allowed only poor discrimination between constitution types and between non-arthrotic and arthrotic joints.

[(11)C]d-threo-methylphenidate PET in patients with Parkinson's disease and essential tremor

Twenty Parkinson's disease (PD) patients, 6 patients with essential tremor and 10 healthy controls were studied with the dopamine transporter ligand [(11)C]d-threo-methylphenidate ([(11)C]dMP) and positron emission tomography (PET) to assess dopamine terminal loss in relation to disease duration and motor disability. Dopamine transporter availability was expressed as [(11)C]dMP binding potential (BP(dMP)) in percentage of the mean of healthy controls. In PD patients (age at onset 57.7 +/- 8.9 yrs; disease duration 5.2 +/- 3.3 yrs; UPDRS motor score 24.2 +/- 9.8; Hoehn & Yahr 2.1 +/- 0.8; mean +/- SD) BP(dMP) was reduced to 30% (range: 11-55%) in the putamen and 52% (range: 14-96%) in the caudate nucleus. BP(dMP) in the putamen closely correlated with the UPDRS motor score (r = -0.79, p < 0.001), and disease duration (r = -0.76, p < 0.001) but not with age at onset. The correlation with the UPDRS score depended on akinesia and rigidity, while the tremor scores were related neither to putamen nor caudate BP(dMP). Interestingly, when plotted over disease duration, PD patients with severe asymmetry of symptoms showed significantly lower BP(dMP) in the contralateral putamen (exponential fit: 34% at onset) than the other PD patients (41% at onset), indicating a different symptomatic threshold of these subgroups and an even closer correlation with the hypothetical "true" disease duration. The exponential fit across all patients indicated a mean symptomatic threshold of 37% contra- and 62% ipsilateral, corresponding with an observed mean BP(dMP) of 51% (average contra- and ipsilateral) in those patients with disease duration less than one year. No differences in BP(dMP) were observed between patients with essential tremor and healthy controls. [(11)C]dMP appears to be a useful and sensitive marker of dopaminergic dysfunction in PD and can be used to assess and monitor disease severity.

The Subchondral Split Line Patterns of the Medial Coronoid Process in Canine Ulnae

The subchondral split line patterns of the canine medial coronoid process (MCP) were compared with fragmentation line patterns of the MCP in case of elbow dysplasia. Split line patterns were determined in paired ulnae from the killed 26 large-breed dogs ranging in age between 0.8 and 15 years and in two ulnae affected by fragmentation of the MCP. The macerated ulnae were degreased with methylene chloride and decalcified in 5% nitric acid. The subchondral bony layer was pierced at right angles in regular intervals using a round needle that was dipped in black liquid acrylic colour. Three main types of split line patterns could be differentiated (i.e. a sagittal type, a transverse type and an intermediate type). In the sagittal type, split lines were aligned in parallel to the lateral border and at right angles to the rim of the tip and medial border of the MCP. In the transverse type, split lines were orientated in a transverse line to both collateral borders. The intermediate type was characterized as a transition type between sagittal and transverse type as the split lines were aligned obliquely to the longitudinal axis of the MCP. These three types corresponded well with the fissure and fragmentation line patterns of the MCP. The present findings strongly suggest an association between split line pattern and type of fragmentation of the MCP.

Deep brain stimulation

During the last decade deep brain stimulation (DBS) has become a routine method for the treatment of advanced Parkinson's disease (PD), leading to striking improvements in motor function and quality of life of PD patients. It is associated with minimal morbidity. The rationale of targeting specific structures within basal ganglia such as the subthalamic nucleus (STN) or the internal segment of the globus pallidus (GPi) is strongly supported by the current knowledge of the basal ganglia pathophysiology, which is derived from extensive experimental work and which provides the theoretical basis for surgical therapy in PD. In particular, the STN has advanced to the worldwide most used target for DBS in the treatment of PD, due to the marked improvement of all cardinal symptoms of the disease. Moreover on-period dyskinesias are reduced in parallel with a marked reduction of the equivalent daily levodopa dose following STN-DBS. The success of the therapy largely depends on the selection of the appropriate candidate patients and on the precise implantation of the stimulation electrode, which necessitates careful imaging-based pre-targeting and extensive electrophysiological exploration of the target area. Despite the clinical success of the therapy, the fundamental mechanisms of high-frequency stimulation are still not fully elucidated. There is a large amount of evidence from experimental and clinical data that stimulation frequency represents a key factor with respect to clinical effect of DBS. Interestingly, high-frequency stimulation mimics the functional effects of ablation in various brain structures. The main hypotheses for the mechanism of high-frequency stimulation are: (1) depolarization blocking of neuronal transmission through inactivation of voltage dependent ion-channels, (2) jamming of information by imposing an efferent stimulation-driven high-frequency pattern, (3) synaptic inhibition by stimulation of inhibitory afferents to the target nucleus, (4) synaptic failure by stimulation-induced neurotransmitter depletion. As the hyperactivity of the STN is considered a functional hallmark of PD and as there is experimental evidence for STN-mediated glutamatergic excitotoxicity on neurons of the substantia nigra pars compacta (SNc), STN-DBS might reduce glutamatergic drive, leading to neuroprotection. Further studies will be needed to elucidate if STN-DBS indeed provides a slow-down of disease progression.

Variation in the ossification process of the anconeal and medial coronoid processes of the canine ulna

This morphological and radiographic study investigates the ossification process of the anconeal and medial coronoid processes of the ulna in a sample of 142 dogs ranging in age from neonatal to 44 weeks. The anconeal process was noted to develop by appositional ossification, formation of a separate ossification center, or a combination of both. Several developmental stages of the ossification center of the anconeal process as well as its anatomic position and radiographic appearance are described. Differences have been noted in the shape of this ossification center as well as the ossification process itself. The medial coronoid process develops exclusively by appositional ossification. Unlike ossification of the anconeal process, ossification of the medial coronoid process was completed earlier (p < 0.05) in smaller than in the larger dogs. In smaller dogs, both the medial coronoid and anconeal processes were found to be mature by the age of 16 weeks. In the larger dogs, ossification of the anconeal process was completed not before 14 weeks of age and ossification of the medial coronoid process was completed about 6 weeks later.

A Morphometric Investigation on Breed-Specific Features Affecting Sagittal Rotational and Lateral Bending Mobility in the Canine Cervical Spine (C3-C7)

Vertebral and inter-vertebral parameters obtained in large breeds (n = 74), small breeds (n = 35), and Dachshunds (n = 30) were compared to reveal potential differences in the range of motion of the cervical spine between these three groups of breeds. Body size normalized dimensions of vertebral and inter-vertebral parameters and correlations between these indicate large canine breeds to have a tendency towards higher range of motion in sagittal rotation and lateral bending compared with Dachshunds and small breeds. Higher mobility in large breeds is based on significantly (P < 0.05) lower vertebral endplate heights and widths, shorter vertebral bodies and longer inter-vertebral discs, wider but shorter cranial and caudal articular surfaces, larger differences in width between caudal and cranial joining facets (compared with Dachshunds from C3/4 to C6/7, compared with small breeds from C4/5 to C5/6), and larger differences in length between caudal and cranial joining facets. Large differences in width between caudal and cranial joining facets were associated with small distances between the most medial (C3/4 to C6/7) and lateral (C3/4 to C5/6) aspects of the articular surfaces as well as with small differences in length between caudal and cranial joining facets (C3/4 to C5/6). This suggests that from C3/4 to C5/6 a higher range of motion in lateral bending is coupled to a lower range of motion in sagittal rotation. The present findings contribute also to explain the higher incidence of degenerative lesions of the cervical spine in large dogs.

mdclust--exploratory microarray analysis by multidimensional clustering

MOTIVATION

Unsupervised clustering of microarray data may detect potentially important, but not obvious characteristics of samples, for instance subgroups of diagnoses with distinct gene profiles or systematic errors in experimentation.

RESULTS

Multidimensional clustering (mdclust) is a method, which identifies sets of sample clusters and associated genes. It applies iteratively two-means clustering and score-based gene selection. For any phenotype variable best matching sets of clusters can be selected. This provides a method to identify gene-phenotype associations, suited even for settings with a large number of phenotype variables. An optional model based discriminant step may reduce further the number of selected genes.

270.Macrophage inhibitory cytokine-1 at the maternal - fetal interface in early pregnancy

Macrophage inhibitory cytokine-1 (MIC-1) is a transforming growth factor-β (TGF-β) superfamily member, first isolated from activated macrophages and subsequently localised in the human placenta. We previously reported that decreased circulating levels in very early pregnancy are associated with subsequent miscarriage. We undertook these current in vitro studies to investigate possible roles for MIC-1 in early pregnancy: (1) regulation of placental matrix metalloproteinase-2 and -9 (MMP-2 and -9); (2) effect on placental apoptosis; and (3) regulation of endometrial stromal cell decidualisation. (1) First trimester placental explant cultures were treated with 100–200 ng/mL MIC-1 � 1/1000 (v/v) anti-MIC-1 antibody. MMP-2 and -9 were measured by gelatin zymography. MMP activation via the plasminogen activation pathway was examined by measuring mRNA expression for urokinase plasminogen activator and its receptor (uPA, uPAR) and type-1 plasminogen activation inhibitor (PAI-1). (2) In first trimester trophoblast explants, apoptosis was induced in vitro with tumor necrosis factor-α (TNF-α) and interferon-β (IFN-β) � 200 ng/mL MIC-1. The pro-apoptosis factor caspase-3 was localised by immunohistochemistry. (3) Using an established model of oestrogen and progesterone induced endometrial stromal cell decidualisation, MIC-1 production was measured and correlated with morphological changes. Cultures were also treated with 20 ng/mL MIC-1. MIC-1 treatment inhibited activation of both MMP-2 and MMP-9 while treatment with anti-MIC-1 antibody blocked the inhibition. uPA, uPAR and PAI-1 mRNA did not change with either treatment. MIC-1 treatment mitigated TNF-α/IFN-β induced trophoblast apoptosis. MIC-1 production increased during induced decidualisation and MIC-1 treatment facilitates further decidualisation in this model. MIC-1 appears to have a number of potentially important functions in the human placenta and decidua consistent with physiological roles in normal placentation. Whether these functions are key to successful pregnancy remains to be studied.

The course of the nasolacrimal duct in brachycephalic cats

Casts of the nasolacrimal duct system were obtained from 50 euthanised cats including brachy-, meso- and dolichocephalic breeds. The course of the nasolacrimal duct, which was assessed radiographically and gross-anatomically, was strongly related to the shape of the skull. In meso- and dolichocephalic cats the nasolacrimal duct formed a dorsally opened arch with the descending part being directed rostroventrally. The main part of the duct passed the nasal cavity in a rather horizontal course parallel to the hard palate and was located ventrally to the lacrimal foramen. However, foreshortening of the face was associated with a right-angled or even acute-angled alignment of the duct. In higher degrees of brachycephaly the main part of the duct ascended beyond the level of the lacrimal foramen and passed the nasal cavity dorsal to the level of the lacrimal foramen. This specific course of the nasolacrimal duct in brachycephalic cats was consistent with a steeper alignment and attachment of the maxilloturbinate. Accessory orifices of the nasolacrimal duct opening into the nasal cavity had never been observed. The present results strongly suggest that the specific course of the nasolacrimal duct in brachycephalic cats might hinder the drainage of the lacrimal fluid irrespective of the diameter of the lumen of the nasolacrimal duct system.

Morphometric investigations of breed-specific features in feline skulls and considerations on their functional implications

A total of 17 parameters (nine lengths, four heights, four widths) was used to characterize the shape of the skull in a sample of 69 pure bred cats. Results of the discriminant analysis confirmed three phenotypically different skull formations, i.e. the round-shaped, the triangular and the cuneiform. Further statistical analyses revealed that the appearance of the skull was especially variable in the case of a round shape and that the lengths had been especially affected by these characteristics. The round shape of the brachycephalic skull was attributed to a reduction in length of the face and braincase as well. In many cases, this condition was associated with disproportional increase in height and width of the braincase and an increase in convexity of the calvaria. The decrease in length of the face was more pronounced at the dorsal surface of the nose than at the palate. Therefore, the inclination of the bony nasal aperture became flatter and the inclination of the maxilloturbinate became steeper. As a result, the ventral nasal meatus changed its direction twice. This condition might predispose to dyspnoea by restricting the air passageways within the nasal cavity. Round-shaped skulls were also associated with a decrease in facial width. Morphological variants that were frequently seen in round-shaped skulls include almost rectangular inclination of the nasal bone and more distant extension of the foramen magnum between the occipital condyles.

The gross and radiographic appearance of sacroiliac ankylosis capsularis ossea in the dog

This study was carried out to determine the incidence and to describe the radiographic appearance of ankylosis capsularis ossea at the canine sacroiliac joint, as well as to determine factors, which might cause radiographic misinterpretation of this finding. Bone specimens of 646 pelves of pure-bred dogs were assessed for morphological evidence of ankylosis capsularis ossea. The lesion was most commonly present at the cranioventral aspects of the sacroiliac joint. More than 50% of adult dogs had signs of being at least mildly affected. Among these, large and giant breeds were most commonly involved. Unlike moderate and severe degrees of this disease, smaller osteophytes had not been visualised on radiographs. For radiographic diagnosis, angled views of the sacrum are recommended. In central views of the sacrum, the presence of increased sacral concavity consistent with increased ilial convexity of the caudal aspect of the sacroiliac contact area might simulate the presence of ankylosis capsularis ossea. The clinical importance of the present findings is discussed in context with human literature.

Differentiation between lumbosacral transitional vertebrae, pseudolumbarisation, and lumbosacral osteophyte formation in ventrodorsal radiographs of the canine pelvis

Ventrodorsal radiographs of the pelvis (n=150) of Rottweilers, Golden Retrievers, and German Shepherd dogs and macerated spines (n=800) from a variety of breeds were assessed for morphological evidence of lumbosacral transitional vertebrae as well as for factors that might lead to radiographic misinterpretation of this condition. Those alterations closely resembling the radiographic appearance of transitional vertebrae were identified to be: (1) calcification of the dorsal and ventral sacroiliac ligaments (=pseudolumbarisation), which might be interpreted as a costal process at S1 (or the corresponding vertebra in cases of numerical vertebral variations); and (2) osteophyte formation at the lumbosacral junction simulating separation of the cranial articular processes from the assembly of the sacral wing as seen in transitional vertebrae.

Bioinformatics for medical diagnostics: assessment of microarray data in the context of clinical databases

MOTIVATION

To identify genes suitable for medical diagnostics microarray data is assessed in the context of clinical databases, which store complex information about the patient phenotype. The wealth of data and lacking standards make it difficult to analyse this kind of data.

RESULTS

We present a workflow for exploratory analysis of microarray data together with clinical data consisting of four steps: definition of clinically meaningful research questions in a masterfile, generation of analysis files, selection and characterization of differentially expressed genes, and estimation of classification accuracy. We applied this workflow to large data sets from the field of cardiology and oncology (n~500 patients). Systematic data management of microarray data and clinical data helps to make results more transparent and comparable.

Osteological and morphometric observations on intervertebral joints in the canine pre-diaphragmatic thoracic spine (Th1-Th9)

The incidence of facet aplasia was investigated in three groups of pure-bred dogs. We examined large breeds (Rough Collies, Doberman Pinschers, Rottweilers, Bernese Mountain Dogs, German Shepherd Dogs), chondrodystrophic breeds (Dachshunds, Pekinese dogs), and small breeds (Yorkshire Terriers, Maltese dogs). Uni- or bilateral aplasia of zygapophyseal (facet) joints was exclusively found in juvenile and adult small dogs, in which the incidence of aplasia ranged from between 26% (Th1) and 63% (Th8). There was no evidence that aplasia of zygapophyseal joints increases the risk of developing intervertebral disc disease or deformative spondylosis in small breeds. By applying the findings of previous empirical studies on intervertebral disc geometry and its biomechanical behaviour on the present morphometric results, there was an indication that the intervertebral disc may well compensate for the functional loss of aplastic zygapophyseal joints in small dogs. Biomechanical factors and their potential role as inducing agents of facet aplasia in the pre-diaphragmatic thoracic spine are also discussed.

Osteological features in pure-bred dogs predisposing to thoracic or lumbar spinal cord compression

Consistent with those vertebral sites most commonly clinically affected by spinal cord compression, body size normalised midsagittal diameters of the caudal vertebral foramen limits T10-T12 were significantly (P<0.05) lower in Dachshunds relative to other breeds. Minimal midsagittal diameters in Yorkshire Terriers and Maltese were noted at T11cd/12cr. However, these diameters were always larger (P<0.05) in small breeds compared to those in Dachshunds and large breeds suggesting that the small breeds investigated are at lower risk of developing clinical signs if a compressive disease occurs at that site. In large breeds, minimal values were present at L1cd/L2cr and in agreement with clinical findings correlate with those spinal sites most susceptible to spinal cord compression in nonchondrodystrophic large breeds. Caudal displacement of the lumbosacral enlargement of the spinal cord relative to the position previously noted in large breeds was confirmed for the Dachshunds and 50% of small breeds. However, caudal displacement was also noticed in the German Shepherd dogs.

Intraoperative microrecordings of the subthalamic nucleus in Parkinson's disease

Microelectrode recordings of single unit neuronal activity were used during stereotactic surgery to define the subthalamic nucleus for chronic deep brain stimulation in the treatment of Parkinson's disease. By using five parallel trajectories, often two to three microelectrodes allow us to recognize subthalamic nucleus (STN) neuronal activity. STN neurons were easily distinguished from cells of the overlying zona incerta and the underlying substantia nigra. During a typical exploratory track, we can observe a very low background noise in the zona incerta and almost complete absence of single cell recording. Penetration of the electrode tip into the STN is characterized by a sudden increase in background activity and single cell activity of spontaneously active neurons. The exit of electrode tip out of the STN corresponds to a decrease in background noise and a loss of single cell activity. Spontaneous neuronal activity increases again when the electrode tips enters the substantia nigra pars reticulata (SNr); however, the activity is less rich than in the STN, indicating a more cell-sparse nucleus. STN neurons are characterized by a mean firing rate of 42.30 +/- 22.00 spikes/sec (mean +/- SD). The STN cells exhibited irregular or bursty discharge pattern. The pattern of single cell activity in the SNr is a more regular tonic activity that can easily be distinguished from the bursting pattern in the STN. The most useful criteria to select a trajectory are (1) the length of an individual trajectory displaying typical STN activity, (2) the bursting pattern of activity, and (3) motor responses typical of the sensorimotor part of the nucleus. In conclusion, microelectrode recording of the subthalamic area improves the accuracy of targeting the STN.

Relevance of image fusion for target point determination in functional neurosurgery

BACKGROUND

For the treatment of medically refractory movement disorders such as Parkinson's disease, essential tremor and primary dystonia, deep brain stimulation (DBS) has become one of the main treatment options. The targets for implantation of the stimulation electrodes are various nuclei within the basal ganglia or the thalamic and subthalamic area. Accurate target localisation is of major importance for outcome and patient safety. The goal of this study was to evaluate the role of image fusion in the determination of target co-ordinates.

METHOD

We conducted a retrospective study on 10 patients in whom 17 DBS electrodes had been implanted. Coordinates of the anterior and posterior commissures and of the DBS targets were compared on pre- and postoperative computerised tomography (CT) and fused CT/magnetic resonance scans. The targets as defined on the images were further compared with the targets derived intra-operatively with microelectrode recordings (MER) and macrostimulation.

FINDINGS

The achievable mean target accuracy was of the order of the diameter of the DBS electrode and of the accuracy of the image fusion algorithm, i.e. about 1 mm. However, the maximal differences were between 1.8 mm and 3.2 mm.

INTERPRETATION

Image fusion is a helpful tool for accurate determination of target point co-ordinates in DBS. In combination with intraoperative, electrophysiological recordings and stimulation which are still considered to be the most reliable localisation methods, image fusion may help to discern the anatomical and functional three-dimensionality of the target nuclei. Image fusion may reduce the number of trajectories needed for intraoperative electrophysiological determination of the optimal electrode localisation and thus lower the risk of complications.

Shape and orientation of articular facets of cervical vertebrae (C3-C7) in dogs denoting axial rotational ability: an osteological study

Macerated cervical vertebrae of 139 adult and 39 juvenile dogs were assessed for morphological evidence of axial rotation, which is denoted by the shape and orientation of the articular facets. The potential effect of the presence of caudal costal foveae at C7 on facet geometry was also investigated. Four variations of caudal facet shape were evident, namely, plane, concave, convex and sigmoid. The earliest onset of change in shape from plane to curved was noticed in juvenile dogs who were older than 8 weeks. The incidence of curved facets denoting axial rotation ability was observed to increase on descending down the cervical spine. Concave caudal facets were more frequently present in males and in large dogs (P < 0.001), compared to Dachshunds and small breeds. The degree of concavity was not related to age but was associated with the transverse distance between the most medial aspects of the caudal and corresponding cranial facets (P < 0.05). In large breeds, the presence of concave caudal facets at C7 was inversely related to the presence of caudal costal foveae (P < 0.01). The effect of axial rotation is discussed in context with clinical literature suggesting that axial rotation might attribute to the development of the wobbler syndrome.