Insights into neuroinflammatory mechanisms of deep brain stimulation in Parkinson's disease

Parkinson's disease, a progressive neurodegenerative disorder, involves gradual degeneration of the nigrostriatal dopaminergic pathway, leading to neuronal loss within the substantia nigra pars compacta and dopamine depletion. Molecular factors, including neuroinflammation, impaired protein homeostasis, and mitochondrial dysfunction, contribute to the neuronal loss. Deep brain stimulation, a form of neuromodulation, applies electric current through stereotactically implanted electrodes, effectively managing motor symptoms in advanced Parkinson's disease patients. Deep brain stimulation exerts intricate effects on neuronal systems, encompassing alterations in neurotransmitter dynamics, microenvironment restoration, neurogenesis, synaptogenesis, and neuroprotection. Contrary to initial concerns, deep brain stimulation demonstrates antiinflammatory effects, influencing cytokine release, glial activation, and neuronal survival. This review investigates the intricacies of deep brain stimulation mechanisms, including insertional effects, histological changes, and glial responses, and sheds light on the complex interplay between electrodes, stimulation, and the brain. This exploration delves into understanding the role of neuroinflammatory pathways and the effects of deep brain stimulation in the context of Parkinson's disease, providing insights into its neuroprotective capabilities.

The interplay between neuroinflammatory pathways and Parkinson's disease

Parkinson's disease, a progressive neurodegenerative disorder predominantly affecting elderly, is marked by the gradual degeneration of the nigrostriatal dopaminergic pathway, culminating in neuronal loss within the substantia nigra pars compacta (SNpc) and dopamine depletion. At the molecular level, neuronal loss in the SNpc has been attributed to factors including neuroinflammation, impaired protein homeostasis, as well as mitochondrial dysfunction and the resulting oxidative stress. This review focuses on the interplay between neuroinflammatory pathways and Parkinson's disease, drawing insights from current literature.

Multicenter Validation of Individual Preoperative Motor Outcome Prediction for Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN DBS) is an established therapy for Parkinson's disease (PD) patients suffering from motor response fluctuations despite optimal medical treatment, or severe dopaminergic side effects. Despite careful clinical selection and surgical procedures, some patients do not benefit from STN DBS. Preoperative prediction models are suggested to better predict individual motor response after STN DBS. We validate a preregistered model, DBS-PREDICT, in an external multicenter validation cohort.

METHODS

DBS-PREDICT considered eleven, solely preoperative, clinical characteristics and applied a logistic regression to differentiate between weak and strong motor responders. Weak motor response was defined as no clinically relevant improvement on the Unified Parkinson's Disease Rating Scale (UPDRS) II, III, or IV, 1 year after surgery, defined as, respectively, 3, 5, and 3 points or more. Lower UPDRS III and IV scores and higher age at disease onset contributed most to weak response predictions. Individual predictions were compared with actual clinical outcomes.

RESULTS

322 PD patients treated with STN DBS from 6 different centers were included. DBS-PREDICT differentiated between weak and strong motor responders with an area under the receiver operator curve of 0.76 and an accuracy up to 77%.

CONCLUSION

Proving generalizability and feasibility of preoperative STN DBS outcome prediction in an external multicenter cohort is an important step in creating clinical impact in DBS with data-driven tools. Future prospective studies are required to overcome several inherent practical and statistical limitations of including clinical decision support systems in DBS care.

Electrode Fixation with Bone Cement or Stimloc® in Deep Brain Stimulation Surgery: A Comparative Study

AIM

The success of deep brain stimulation (DBS) surgeries depends on the implantation of electrodes toward the target nucleus and fixation to the cranium. This study examined the postoperative outcomes of electrode fixation using bone cement and Stimloc® in patients with Parkinson\'s disease (PD) who underwent subthalamic nucleus (STN) DBS.

MATERIAL AND METHODS

Between 2016 and 2018, permanent electrode fixation was performed in 30 patients with PD, of which 15 received bone cement and the remaining 15 received Stimloc®. Data regarding preoperative Unified Parkinson's Disease Rating Scale (UPDRS) III scores, levodopa equivalent daily dose (LEDD) values, surgery duration, and the fixation technique used were recorded. Brain computed tomography was performed for early postoperative evaluation of pneumocephalus and possible hematoma as well as for the determination of migration 1 year postoperatively. UPDRS III scores and LEDD values were re-evaluated 1 year postoperatively; surgery duration, clinical effectiveness, and complication rates were compared between the two fixation techniques.

RESULTS

A statistically significant difference in application time was observed between the two techniques (bone cement: 21 min, Stimloc®: 6 min). After 1 year from surgery, 0.92- and 0.88-mm migrations were observed in the bone cement and Stimloc® groups, respectively. A significant correlation between migration and the pneumocephalus volume was observed in both groups. No differences were observed between the groups regarding infection, migration, pneumocephalus volume, wound erosion, and clinical outcomes.

CONCLUSION

Stimloc® is preferred over bone cement for electrode fixation in DBS surgeries as it is associated with shorter application duration; this increases patient comfort and tolerance during awake surgery. Clinical efficacy and complication rates associated with both techniques are similar.

The Alteration of Neurogenesis and Pathological Markers in Alzheimer's Disease After Deep Brain Stimulation

Alzheimer's disease (AD) is the most common type of dementia that causes disabilities in memory formation and activities of daily living. Unfortunately, pharmacologic treatments have minimal and short-lasting effects on the disease. With the increasing aging population, investigations into therapeutic strategies for AD that lead to delay in disease progression would significantly reduce the global burden of AD. Deep brain stimulation (DBS) is considered therapeutic for several conditions, such as movement disorders and some psychiatric diseases. Preclinical and clinical studies that used DBS as a treatment modality demonstrate the safety of DBS in AD and suggest potential memory improvements after surgery. Nevertheless, more studies are needed to understand the therapeutic mechanism of DBS. In this review, we summarize studies on DBS in various targets for AD and discuss DBS-induced changes in neurogenesis and pathological markers in AD.

Subthalamic Nucleus Deep Brain Stimulation in a Patient with Severe Axial Symptoms and Suboptimal Levodopa Responsive Parkinson's Disease

BACKGROUND

Deep brain stimulation (DBS) is a well-established treatment option for improving function and quality of life in carefully selected patients with Parkinson's disease (PD). Patient selection is a crucial step that should be carried out by an experienced multidisciplinary team according to the proposed inclusion and exclusion criteria to increase the quality of life (QoL) of patients.

CASE

A 47-year-old bedridden woman with a 20-year history of PD presented with levodopa-unresponsive tremor and severe axial symptoms. Despite various antiparkinsonian medications, a suboptimal improvement was observed with the levodopa challenge test. After detailed evaluations, she underwent bilateral Subthalamic nucleus DBS (STN-DBS). During 2-year-follow-up her axial symptoms improved significantly leading to a better QoL.

CONCLUSION

Although levodopa-resistant axial symptoms are considered a relative contraindication to DBS surgery, this case report demonstrates that with an interdisciplinary approach and an accurate assessment of symptoms, even bedridden and late-stage selected PD cases may benefit from DBS.

Deep Brain Stimulation of the Globus Pallidus Internus for Secondary Dystonia: Clinical Cases and Systematic Review of the Literature Regarding the Effectiveness of Globus Pallidus Internus versus Subthalamic Nucleus

OBJECTIVE

Deep brain stimulation (DBS) is a frequently applied therapy in primary dystonia. For secondary dystonia, the effects can be less favorable. We share our long-term findings in 9 patients with severe secondary dystonia and discuss these findings in the light of the literature.

METHODS

Patients who had undergone globus pallidus internus (GPi)-DBS for secondary dystonia were included. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) scores, clinical improvement rates, follow-up periods, stimulation parameters and the need for internal pulse generator replacements were analyzed. The PubMed and Google Scholar databases were searched for articles describing GPi-DBS and subthalamic nucleus (STN)-DBS only for secondary dystonia cases. Keywords were "dystonia," "deep brain stimulation," "GPi," "dystonia," "deep brain stimulation," and "STN."

RESULTS

A total of 9 secondary dystonia patients (5 male, 4 female) had undergone GPi-DBS with microelectrode recording in our units. The mean follow-up period was 29 months. The average BFMDRS score was 58.2 before the surgery, whereas the mean value was 36.5 at the last follow-up of the patients (mean improvement, 39%; minimum, 9%; maximum, 63%). In the literature review, we identified 264 GPi-DBS cases (mean follow-up, 19 months) in 72 different articles about secondary dystonia. The mean BFMDRS improvement rate was 52%. In 146 secondary dystonia cases, reported in 19 articles, STN-DBS was performed. The average follow-up period was 20 months and the improvement in BFMDRS score was 66%.

CONCLUSIONS

Although GPi-DBS has favorable long-term efficacy and safety in the treatment of patients with secondary dystonia, STN seems a promising target for stimulation in patients with secondary dystonia. Further studies including a large number of patients, longer follow-up periods, and more homogenous patients are necessary to establish the optimal target for DBS in the management of secondary dystonias.

Effects of Deep Brain Stimulation of the Subthalamic Nucleus on the Postoperative Levodopa Response: One Year Follow Up

AIM

To investigate the effect of preoperative levodopa responsiveness to clinical outcomes in the first postoperative year, and to evaluate the changes in the postoperative levodopa responsiveness in patients undergoing subthalamic nucleus (STN) deep brain stimulation (DBS).

MATERIAL AND METHODS

Forty-nine Parkinson?s Disease (PD) patients undergoing bilateral DBS of the STN were included in this study. Their clinical motor symptoms were assessed preoperatively by UPDRS Part III score in both OFF and ON medication states. Postoperatively, the assessments were obtained in three consecutive conditions. Preoperatively and postoperatively, the percentage difference between these two scores was evaluated as levodopa response.

RESULTS

Mean age was 54.6 ± 9 years (27?70). Levodopa response significantly decreased postoperatively by 56% a year. Compared with preoperative med on and postoperative stim on / med on scores, the clinical results of the first year were obtained and an improvement of 25% on the UPDRS 3 score was observed. Compared with preoperative levodopa response and clinical outcomes, better clinical results were obtained in patients with higher preoperative levodopa response (p < 0.05).

CONCLUSION

In this study, we confirm that the response of L-dopa decreases after DBS of the STN. The reasons for this finding are not clear. However, DBS of the STN allows for the reduction of PD medications and improvement of daily life activities, motor function, motor fluctuations, and dyskinesia.

Characterizing the Intraoperative Microelectrode Recording-Induced Microlesion Effect on Motor Symptoms in Patients with Parkinson's Disease Undergoing Deep Brain Stimulation of the Subthalamic Nucleus

AIM

To investigate microelectrode recording (MER)-induced microlesion effect (MLE) on the motor symptoms of 30 patients with Parkinson’s disease (PD) who underwent deep brain stimulation of the subthalamic nucleus.

MATERIAL AND METHODS

MER-induced MLE was evaluated based on the difference between tremor, rigidity, and bradykinesia scores in the preoperative off-state and intraoperative state following MER and before test stimulation.

RESULTS

MLE scores improved by 21.7% [left (L) side] and by 13.6% [right (R) side] from baseline (p < 0.05). Tremor scores improved by 31.5% (L) and by 14.2% (R) (p < 0.05), rigidity scores improved by 17.3% (L) and by 14.2% (R) (p < 0.05) and bradykinesia scores improved by 20.6% (L) and by 11.5% (R) (p < 0.05) from baseline. There was no significant difference between MLE and the number of microelectrodes used (p > 0.05).

CONCLUSION

MER-induced MLE improved motor symptoms and was not correlated with the number of microelectrodes used during the procedure.

Stereotactic accuracy and frame mounting: A phantom study

Background:

Frame mounting is considered one of the most critical steps in stereotactic neurosurgery. In routine clinical practice, the aim is to mount the frame as symmetrical as possible, parallel to Reid’s line. However, sometimes, the frame is mounted asymmetrically often due to patient-related reasons.

Methods:

In this study, we addressed the question whether an asymmetrically mounted frame influences the accuracy of stereotactic electrode implantation. A Citrullus lanatus was used for this study. After a magnetic resonance imaging scan, symmetric and asymmetric mounting of the frame, which could occur in clinical scenarios, was performed with computed tomography (CT). Three different stereotactic software packages were used to analyze the results. In addition, manual calculations were performed by two different observers.

Results:

Our results show that an asymmetrically mounted frame (deviated, tilted, or rotated) does not affect the accuracy in the mediolateral axis (X-coordinate) or the anteroposterior axis (Y-coordinate). However, it can lead to a clinically relevant error in the superoinferior axis (Z-coordinate). This error was largest with manual calculations.

Conclusion:

These results suggest that asymmetrical frame mounting can lead to stereotactic inaccuracy in the superoinferior axis (Z coordinate).

Statistical Shape Analysis of Subthalamic Nucleus in Patients with Parkinson Disease

OBJECTIVE

Subthalamic nucleus (STN) is the most targeted localization in the treatment of Parkinson disease (PD) with deep brain stimulation. However, no studies have been found in the literature about possible shape changes of STN in the literature. We aimed to investigate possible shape changes in the STN and the relationship between shape changes and disease duration in PD patients by using statistical analysis.

METHODS

Patients who were diagnosed with idiopathic PD and controls were enrolled in this study. Age, sex, and disease duration of all cases were recorded. Turbo-spin-echo T2-weighted axial series parallel to the skull base in each case containing midbrain images were obtained, including the whole STN. Standard anatomic landmarks were selected and marked on each digital image using a special software in all cases. Statistical geometric shape and deformation analysis of STN was performed in 2 groups.

RESULTS

Forty-three patients with PD and 50 age/sex-matched controls were enrolled in this study. There were statistically significant left and right STN shape differences between the groups. Maximum deformation was seen in the dorsolateral parts of both STNs. General shape variability of the STNs was found on the left (0.096) and right (0.049).

CONCLUSIONS

Significant shape differences and remarkable deformation of STN are seen in patients with PD compared with controls. Maximum deformation was observed in the dorsolateral part of the STN, and with the increase in the duration of the PD, shape differences and deformations became more prominent.

Microelectrode Recording for Deep Brain Stimulation of the Subthalamic Nucleus in Patients with Advanced Parkinson's Disease: Advantage or Loss of Time?

AIM

To investigate the effect of using microelectrode recording (MER) on the length of time required to carry out a deep brain stimulation (DBS) procedure of the subthalamic nucleus in patients with Parkinson's disease (PD).

MATERIAL AND METHODS

The time required to include MER in the DBS operation was calculated for the first and second sides in 24 patients with PD. The number of microelectrodes used on each trajectory for the first and second sides, and the percentage of permanent electrodes implanted on each trajectory for the first and second sides, were quantified.

RESULTS

The average times taken to use MER were 23.4 ± 6.2 minutes, 17.4 ± 6.5 minutes, and 41.2 ± 6.3 minutes for the first side, second side and total procedure, respectively. In 75% of patients, the permanent electrode was implanted at the planned target site for the first side, and in 61% of patients for the second side.

CONCLUSION

MER extends the time required to carry out the DBS procedure. However, during surgery, it provides real-time information on the electrodes' neurophysiological locations and helps the surgical team choose an alternative target if the planned target does not produce satisfying results.

Management of Hardware Related Infections after DBS Surgery: A Cost Analysis

AIM

To investigate the costs of treating the infection with antibiotics only with the risk of surgery when unsuccessful versus immediate removal followed by re-implantation in patients with deep brain stimulation (DBS) hardware infection.

MATERIAL AND METHODS

We calculated the costs of the different strategies through a standard costing procedure. A decision model has been applied to establish the average treatment cost per patient representative for a clinical setting where both strategies are employed. Subsequently, a sensitivity analysis has been performed to assess the influence of clinical assumptions regarding the effectiveness of antibiotics treatment on average treatment costs.

RESULTS

The costs of treating a case of DBS hardware infection with immediate internal pulse generator (IPG) replacement surgery were ?29,301 compared to ?9499 for successful antibiotic treatment. For antibiotic treatment followed by IPG replacement surgery the total costs were ?38,741. Antibiotic treatment alone was successful in 44% (4/9) of the included cases of DBS infection, resulting in average treatment costs per patient of ?25,745. Trying to resolve DBS hardware infections initially with antibiotics reduced treatment costs by 12.1%.

CONCLUSION

Treatment with antibiotics with the risk of a later removal when unsuccessful was a more valuable strategy in terms of costs when compared to immediate surgical intervention in cases of hardware-related infections in DBS surgeries.

Infections in deep brain stimulation: Shaving versus not shaving

Background:

To report our experience of infections in deep brain stimulation (DBS) surgeries comparing shaving versus no shaving of cranial hair. Nonshaving is strongly preferred by patients due to aesthetic and psychological factors.

Methods:

This study is a prospective follow-up of the infection rate in 43 nonshaven DBS cases between April 2014 and December 2015 compared to our former infection rate with shaving in our center. Minimum follow-up was 6 months. All patients, except 7 epilepsy patients, received implantation of the electrodes together with the extension cables and internal pulse generator in one session.

Results:

In 43 nonshaven patients, a total of 81 electrodes were implanted or revised with a mean follow-up of 16 months. One patient (2.32%) developed an infection of the implanted DBS-hardware and was treated with antibiotics.

Conclusion:

In our experience nonshaving of cranial hair in DBS surgery does not lead to more infections when compared to shaving. We have changed our protocol to nonshaving based on these findings.

Perioperative Technical Complications in Deep Brain Stimulation Surgeries

AIM

Deep brain stimulation (DBS) surgeries are multi-faceted and the various steps are interconnected. Since its first implementation, the method of DBS surgery has undergone changes. We have encountered several expected and also non-expected perioperative technical complications in the past seventeen years. Here, we describe the stereotactic frame, stereotactic localizer and planning station related complications and how we have managed them as much as possible.

MATERIAL AND METHODS

This study is a retrospective qualitative analysis of the documented technical events encountered during DBS surgeries from 1999 onwards. We have collected these events from a cohort of approximately 921 DBS electrodes implantations from the centers of the authors.

RESULTS

Stereotactic frame related complications included movement related fixation problems, head anatomy related problems, and lack of maintenance related issues. Localizer related complications were compatibility issues of the stereotactic localizer and planning station, field of view effect on fiducials, air bubbles in localizers using liquid solutions, and disengaged localizer effect. Planning station related complications included image fusion failures and cerebrospinal fluid signal effect on image fusion.

CONCLUSION

The road to success in DBS therapy passes through the ability to cope with surgical and technical complications. Each step is unconditionally connected to the other, and detection of the problems that can be encountered in advance and preparations for these negative conditions are the key to success for the group responsible for executing the therapy. We are still learning from these events and advance our surgical approaches.

Effect of Age and Disease Duration on the Levodopa Response in Patients with Advanced Parkinson's Disease for Deep Brain Stimulation of the Subthalamic Nucleus

Background

Deep brain stimulation (DBS) has become a preferred option for the treatment of motor symptoms in patients with advanced Parkinson’s disease (PD). A good levodopa response (LR) is considered the most important criterion in determining the suitability of a patient for DBS. However, the effect of age and disease duration (DD) on the LR is still a subject of discussion.

Objective

Here, we investigated the effect of age and DD on the preoperative LR in PD patients to be selected for DBS.

Methods

From August 2011 to May 2015, 54 consecutive patients (29 men and 25 women) with advanced PD were evaluated for DBS of the STN and included in this retrospective study.

Results

Thirty-seven patients were found suitable for DBS of the STN and 29 of them underwent bilateral surgery. We found no significant correlation between DD and the LR. However, there was a significant negative correlation between the patients’ age and the LR.

Conclusion

The results indicate that the patients’ age, rather than DD, has a negative effect on the LR. The study, therefore, indicates that PD patients with an advanced age and with a poor LR are not good candidates for DBS of the STN.

Deep Brain Stimulation of the Rat Subthalamic Nucleus Induced Inhibition of Median Raphe Serotonergic and Dopaminergic Neurotransmission

AIM

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) relieves motor dysfunction in advanced Parkinson's disease (PD). However, STN DBS treated patients can experience unpleasant and debilitating psychiatric side effects such as depression and impulsivity. The neural basis of these psychiatric effects has been linked to a dysfunction of 5-hydroxytryptamine (5-HT, serotonin) neurotransmission. STN DBS inhibited activity of 5-HT cell bodies in the dorsal raphe nucleus (DRN). Another important 5-HT source is located in the median raphe nucleus (MRN), which also contains a population of dopamine neurons. The effects of STN DBS on the MRN are unknown. Here, we test the hypothesis that STN DBS reduces 5-HT and dopaminergic function in the MRN, which may contribute to the psychiatric side effects of STN stimulation.

MATERIAL AND METHODS

Bilateral STN DBS was applied in a freely moving rat model. Following STN DBS, rats were sacrificed and the brains were processed for c-Fos, 5-HT and tyrosine hydroxylase (TH) immunohistochemistry.

RESULTS

We found that STN DBS significantly lowered c-Fos expression compared to non-stimulated controls indicating reduced neuronal activity. Moreover, the mean optical density values of 5-HT and TH cells in the MRN was significantly lower compared to controls.

CONCLUSION

These results show that STN DBS inhibits 5-HT and dopamine neurotransmission in the MRN.

A detailed analysis of intracerebral hemorrhages in DBS surgeries

OBJECTIVES

Deep brain stimulation is nowadays a frequently performed surgery in patients with movement disorders, intractable epilepsy, and severe psychiatric disorders. The most feared complication of this surgery is an intracerebral hemorrhage due to the electrode placement, either for intraoperative electrophysiology (microelectrode recording) and/or implantation of the final electrode (macroelectrode). Here, we have investigated the risk of developing an intracerebral hemorrhage in our cohort of deep brain stimulation patients over a period of 15 years.

PATIENTS AND METHODS

We have collected demographic data and analyzed the effect of performing surgery with single-electrode versus multiple electrode guided DBS. The effect of using single-dose versus double-dose contrast enhanced MRI to visualize vessels for the electrode trajectory planning has been investigated as well.

RESULTS

We have found that the overall calculated risk of an intracerebral hemorrhage in our series was 1.81% per patient, 0.3% per recording electrode and 0.23% per brain insertion. While three out of four patients recovered without neurological deficits, there was one mortality in a patient with cardiovascular comorbidities. Statistical comparisons between the groups of single-electrode versus multiple electrode guided surgery and single-dose gadolinium versus double-dose contrast enhanced MRI revealed no significant differences. In addition, there was no meaningful correlation between the age at surgery and the risk of bleeding.

CONCLUSION

We have found that the risk of developing an intracerebral hemorrhage due to deep brain stimulation surgery is low. The clinical course of the patients with an intracerebral hemorrhage was generally favorable.

Current perspectives on deep brain stimulation for severe neurological and psychiatric disorders

Deep brain stimulation (DBS) has become a well-accepted therapy to treat movement disorders, including Parkinson's disease, essential tremor, and dystonia. Long-term follow-up studies have demonstrated sustained improvement in motor symptoms and quality of life. DBS offers the opportunity to selectively modulate the targeted brain regions and related networks. Moreover, stimulation can be adjusted according to individual patients' demands, and stimulation is reversible. This has led to the introduction of DBS as a treatment for further neurological and psychiatric disorders and many clinical studies investigating the efficacy of stimulating various brain regions in order to alleviate severe neurological or psychiatric disorders including epilepsy, major depression, and obsessive-compulsive disorder. In this review, we provide an overview of accepted and experimental indications for DBS therapy and the corresponding anatomical targets.

Transgenic Rat Models of Huntington's Disease

Several animal models for Huntington's disease (HD) have been created in order to investigate mechanisms of disease, and to evaluate the potency of novel therapies. Here, we describe the characteristics of the two transgenic rat models: transgenic rat model of HD (fragment model) and the Bacterial Artificial Chromosome HD model (full-length model). We discuss their genetic, behavioural, neuropathological and neurophysiological features.

The antidepressant effects of ventromedial prefrontal cortex stimulation is associated with neural activation in the medial part of the subthalamic nucleus

The nucleus accumbens (NAc), ventromedial prefrontal cortex (vmPFC), and cingulate gyrus (Cg) are key regions in the control of mood-related behaviors. Electrical stimulation of these areas induces antidepressant-like effects in both patients and animal models. Another structure whose limbic connections are receiving more interest in the context of mood-related behaviors is the medial part of the subthalamic nucleus (STN). Here, we tested the hypothesis that the mood-related effects of NAc, vmPFC, and Cg are accompanied by changes in the neural activity of the STN. We performed high-frequency stimulation (HFS) of the NAc, vmPFC, and Cg. Animals were behaviorally tested for hedonia and forced swim immobility; and the cellular activities in the different parts of the STN were assessed by means of c-Fos immunoreactivity (c-Fos-ir). Our results showed that HFS of the NAc and vmPFC, but not Cg reduced anhedonic-like and forced swim immobility behaviors. Interestingly, there was a significant increase of c-Fos-ir in the medial STN with HFS of the vmPFC, but not the NAc and Cg as compared to the sham. Correlation analysis showed that the medial STN is associated with the antidepressant-like behaviors in vmPFC HFS animals. No behavioral correlation was found with respect to behavioral outcome and activity in the lateral STN. In conclusion, HFS of the vmPFC induced profound antidepressant-like effects with enhanced neural activity in the medial part of the STN.

Does probe's eye subthalamic nucleus length on T2W MRI correspond with microelectrode recording in patients with deep brain stimulation for advanced Parkinson's disease?

AIM

Subthalamic nucleus (STN) deep brain stimulation (DBS) has become a well-accepted treatment for patients with advanced Parkinson's disease (PD). During surgical planning for DBS, the length of the STN is taken into account and verified during microelectrode recording (MER) intraoperatively. Here, we addressed the question to which extent the length of the STN measured with the T2 weighted MRI in the probe's eye view corresponded with the intraoperatively determined length of the STN with MER.

MATERIAL AND METHODS

We included 10 consecutive Parkinson's disease patients who underwent STN DBS surgery. The length of the STN in the probe's eye view mode was calculated along the trajectory of the central MER electrode crossing the STN.

RESULTS

Our analysis showed no statistical difference between the length of the STN measured with the T2 weighted probe's eye view mode and the MER (right STN length 5.8 ± 0.9 mm MRI vs. 6.3 ± 0.5 mm MER, p > 0.05; left STN length 5.6 ± 0.4 mm MRI vs 5.8 ± 1 mm MER, p > 0.05).

CONCLUSION

This means that the entry and the exit of the STN can be adequately estimated using the probe's eye view preoperatively.

Volumetric analysis of the subthalamic and red nuclei based on magnetic resonance imaging in patients with Parkinson's disease

Parkinson's disease (PD) is associated with degeneration of the dopaminergic neurons in the substantia nigra. The subthalamic nucleus (STN) plays a pivotal role in the pathogenesis. However, there is not much known about the morphological changes in the STN. The red nucleus (RN) has many connections with the motor coordinating pathways although it is not primarily involved in the pathogenesis. In this study we aimed to compare the volumes of the STN and RN measured by magnetic resonance imaging in PD patients and controls to investigate how these structures are affected at the morphological level. Twenty patients with PD and twenty age/sex matched controls were enrolled in this study. Severity score was determined by Hoehn & Yahr staging: 6 at stage II and 14 at stage III in med-off state. Imaging was performed by a 1.5 Tesla (T) MR scanner. Measurements of total brain and normalized STN and RN volumes were performed by manual planimetry using Image J software. No statistically significant differences were observed between two groups based on age or gender and disease stage and nuclei volumes. The total estimated brain volumes were not different between PD patients and controls. However, normalized volumes of the STN and RN were 14% and 16% larger, respectively, in PD patients compared to the controls (p < 0.05). Our findings suggest that the volumes of the STN and RN are increased in patients with PD. These changes possibly reflect the altered metabolic activity of these regions demonstrated by neurophysiological studies.

Targeting thalamic tremor cells in deep brain stimulation for multiple sclerosis-induced complex tremor

BACKGROUND

Tremor is an important cause of disability in patients with multiple sclerosis (MS). It is an ongoing debate as to which brain region should be targeted in MS patients with complex tremors.

CASE DESCRIPTION

Here, we describe our experience with targeting thalamic tremor cells in the ventro-intermediate/ventro-oralis posterior (Vim/Vop) region in a patient with MS related complex tremor. Intraoperative multiple-microelectrode recordings showed the existence of tremor cells. Test stimulation produced the best effect when performed at the regions where tremor cells were recorded. Postoperative examination revealed a substantial improvement of the tremor.

CONCLUSION

Our case observation reveals the existence of a neurophysiological target for deep brain stimulation (DBS) in MS related tremor.

Deep brain stimulation of the subthalamic nucleus in Parkinson's disease: Why so successful?

The subthalamic nucleus (STN), historically referred to as the corpus Luysii, is a relatively small nucleus located in the junction between the diencephalon and midbrain. An important discovery was made in the late 1980s by Miller and DeLong putting the focus on the STN demonstrating abnormal hyperactivity in this area in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treated non-human primates. Shortly after, Benazzouz and colleagues showed STN deep brain stimulation (DBS) to significantly improve MPTP induced parkinsonian symptoms, including rigidity and bradykinesia in monkeys. In the same year, Pollak et al. were the first to publish a French case report describing the potential of STN DBS in a patient with advanced Parkinson's disease (PD) in whom they observed improvement of akinesia. Many other prospective studies showed similar improvements of motor symptoms and the lowering of required levodopa dosage. The great success of STN DBS for the treatment of advanced PD is underlined by the growing number of patients treated. STN DBS also provided additional insight into the role of the STN, which is important not only in motor control but also in cognitive and emotional functions.

Use of topical landmarks for percutaneous projection of intracranial tumors for neurosurgical oncology

AIM

The objective of this study was to introduce a surgical navigation method which provides a safe, quick and effective access to cortical and subcortical tumors, along with a review of other methods in use for this purpose.

MATERIAL AND METHODS

53 patients have been operated using this technique. The area overlying the tumor is shaved and one half of a smoothly cut hazelnut is taped on the skin. The precise localization of the hazelnut is confirmed with MRI and then stained. After general anesthesia, the stained impression is projected firstly to the bone, dura and then cortex respectively by the Midas Rex cutting tip. Cortical landmarks surrounding the tumor's cortical projection are further confirmed with ultrasonography.

RESULTS

After removal, cortical and subcortical tumors were separately graded for efficiency. Grade 1 and 2 were accepted as precise access. Our method accordingly yielded 95.2% and 90.6% success rates for cortical and subcortical tumors respectively.

CONCLUSION

Considering the method's success rate along with its inexpensiveness and modest technical requirements, it is believed that this method can be of widespread use.