Advances in functional neurosurgery for Parkinson's disease

[Movement Disorders: What Are You Doing? What Can We Do?]

Movement Disorders: What Are You Doing? What Can We Do? Abstract. Disturbances of movement are common and varied. Frequent causes are systemic diseases such as Parkinson's syndromes and the essential tremor. Treatment options in practice and hospital include conservative, predominantly drug strategies such as oral administration of dopamine precursors or agonists, and pharmacological or non-pharmacological escalation strategies such as intramuscular botulinum toxin A injections, the subcutaneous or enteral drug pumps for apomorphine or levodopa and carbidopa, the effective deep brain stimulation and the novel focused ultrasound therapy, which are bound to highly specialized centers and should be considered as treatment option quite earlier and more frequently.

Morphometric Study of the Internal Globus Pallidus Using the Robert, Barnard, and Brown Staining Method

BACKGROUND

The globus pallidus internus (Gpi) is a major target in functional neurosurgery. Anatomical studies are crucial for correct planning and good surgical outcomes in this region. The present study described the anatomical coordinates of the Gpi and its relationship with other brain structures and compared the findings with those from previous anatomical studies.

METHODS

We obtained 35 coronal and 5 horizontal brain specimens from the Department of Anatomy and stained them using the Robert, Barnard, and Brown technique. After excluding defective samples, 60 nuclei were analyzed by assessing their distances to the anatomical references and the trajectories to these nuclei.

RESULTS

The barycenter of the Gpi was identified at the level of the mammillary bodies and 1 cm above the intercommissural plane. Thereafter, the distances to other structures were found. The mean ± standard deviation distance was 15.62 ± 2.66 mm to the wall of the third ventricle and 17.02 ± 2.69 mm to its midline, 4.74 ± 1.12 mm to the optic tract, 2.51 ± 0.8 mm and 13.56 ± 2 mm to the internal and external capsule, and 21.3 ± 2.44 mm to the insular cortex. The cortical point of entry should be located 22.03 ± 4.34 mm to 48.74 ± 4.44 mm from the midline.

CONCLUSION

The Gpi has less variability in distance to closer anatomical references, such as the optic tract and internal capsule. Distant locations showed a more inhomogeneous pattern. Anatomical studies such as ours are important for the development of new therapeutic approaches and can be used as a basis for new research involving volumetric and specific group analyses.

Parkinson's disease: Diagnosis and appreciation of comorbidities

Parkinson's disease (PD) is a complex neuropsychiatric disorder that manifests with a variety of motor and nonmotor symptoms. Its incidence increases with age. It is important for clinicians to be able to distinguish symptoms of aging and other comorbidities from those of PD. The diagnosis of PD has traditionally been rendered using strict criteria that mainly rely on the cardinal motor symptoms of rest tremor, rigidity, and bradykinesia. However, newer diagnostic criteria proposed by the Movement Disorders Society for diagnosis of PD collectively reflect a greater appreciation for the nonmotor symptoms. The treatment of PD remains symptomatic and the most noticeable improvements have been documented in the motor symptoms. Levodopa remains the gold standard for therapy, however there are now many other potential medical and surgical treatment strategies. Nonmotor symptoms have been shown to affect quality of life more than the motor symptoms. There is ongoing research into symptomatic and disease modifying treatments. Given the multisystem involvement in PD, an interdisciplinary patient-centered approach is recommended by most experts. This chapter addresses first the diagnostic approach and the many geriatric considerations. This is followed by a review of the nonmotor symptoms. Finally, a summary of current treatment strategies in PD is presented along with potential treatment complications.

Magnetic Resonance-Guided Focused Ultrasound in Neurosurgery: Taking Lessons from the Past to Inform the Future

Magnetic resonance-guided focused ultrasound (MRgFUS) is a new emerging neurosurgical procedure applied in a wide range of clinical fields. It can generate high-intensity energy at the focal zone in deep body areas without requiring incision of soft tissues. Although the effectiveness of the focused ultrasound technique had not been recognized because of the skull being a main barrier in the transmission of acoustic energy, the development of hemispheric distribution of ultrasound transducer phased arrays has solved this issue and enabled the performance of true transcranial procedures. Advanced imaging technologies such as magnetic resonance thermometry could enhance the safety of MRgFUS. The current clinical applications of MRgFUS in neurosurgery involve stereotactic ablative treatments for patients with essential tremor, Parkinson's disease, obsessive-compulsive disorder, major depressive disorder, or neuropathic pain. Other potential treatment candidates being examined in ongoing clinical trials include brain tumors, Alzheimer's disease, and epilepsy, based on MRgFUS abilities of thermal ablation and opening the blood-brain barrier. With the development of ultrasound technology to overcome the limitations, MRgFUS is gradually expanding the therapeutic field for intractable neurological disorders and serving as a trail for a promising future in noninvasive and safe neurosurgical care.

Frameless Stereotaxis for Subthalamic Nucleus Deep Brain Stimulation: An Innovative Method for the Direct Visualization of Electrode Implantation by Intraoperative X-ray Control

The recent introduction of frameless devices has enabled stereotactic neurosurgery to reach a level of accuracy that is comparable to traditional frame-based methodologies. Among frameless devices, the Nexframe appears to be very useful in implanting electrodes into the subthalamic nucleus or other structures for deep brain stimulation in Parkinson’s disease. However, frameless devices, including the Nexframe, limit the possibility of intraoperative visual control of the placement of electrodes in the brain. Utilizing intraoperative O-arm Computed tomography (CT) scan or high-field Magnetic Resonance Imaging (MRI) could overcome this limitation, but their high cost restricts their use. Thus, in this paper we propose an innovation in Nexframe surgical planning that allows the intraoperative use of a C-arm X-ray apparatus to establish: (1) the progression of the electrode guide tube and the electrode in the brain; (2) the accuracy of the electrode trajectory; and (3) the correct attainment of the target. The proposed frameless technique using the Nexframe has been developed and successfully applied in our practice. It was shown to be helpful in overcoming the major issues that are usually encountered when electrodes are placed in the brain with frameless neurosurgery and reduced the risk of having to re-operate on patients to reposition the electrodes.

Articulation Features of Parkinson's Disease Patients with Subthalamic Nucleus Deep Brain Stimulation

BACKGROUND

Voice and speech disorders are one of the most important issues after subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD) patients. However, articulation features in this patient population remain unclear.

OBJECTIVE

We studied the articulation features of PD patients with STN-DBS.

METHODS

Participants were 56 PD patients treated with STN-DBS (STN-DBS group) and 41 patients treated only with medical therapy (medical-therapy-alone group). Articulation function was evaluated with acoustic and auditory-perceptual analyses. The vowel space area (VSA) was calculated using the formant frequency data of three vowels (/a/, /i/, and /u/) from sustained phonation task. The VSA reportedly reflects the distance of mouth/jaw and tongue movements during speech and phonation. Correlations between acoustic and auditory-perceptual measurements were also assessed.

RESULTS

The VSA did not significantly differ between the medical-therapy-alone group and the STN-DBS group in the off-stimulation condition. In the STN-DBS group, the VSA was larger in the on-stimulation condition than in the off-stimulation condition. However, individual analysis showed the VSA changes after stopping stimulation were heterogeneous. In total, 89.8% of the STN-DBS group showed a large VSA size in the on- than in the off-stimulation condition. In contrast, the VSA of the remaining patients in that group was smaller in the on- than the off-stimulation condition.

CONCLUSIONS

STN-DBS may resolve hypokinesia of the articulation structures, including the mouth/jaw and tongue, and improve maximal vowel articulation. However, in the on-stimulation condition, the VSA was not significantly correlated with speech intelligibility. This may be because STN-DBS potentially affects other speech processes such as voice and/or respiratory process.

Drug-Induced Dyskinesia, Part 1: Treatment of Levodopa-Induced Dyskinesia

Dyskinesias encompass a variety of different hyperkinetic phenomenologies, particularly chorea, dystonia, stereotypies, and akathisia. Levodopa-induced dyskinesia (LID) is one of the main types of drug-induced dyskinesia, occurring in patients with Parkinson's disease (PD) who have been treated with levodopa for long time, but this side effect may be encountered even within a few weeks or months after initiation of levodopa therapy. Based on the temporal pattern in relationship to levodopa dosing, LIDs are divided into "peak-dose dyskinesia," "diphasic dyskinesia," and "wearing off" or "off-period" dyskinesia, of which peak-dose dyskinesia is the most common, followed by off-period, and then diphasic dyskinesia. Treatment strategy includes identifying the kind of dyskinesia and tailoring treatment accordingly. Peak-dose dyskinesia is treated mainly by reducing individual doses of levodopa and adding amantadine and dopamine agonists, whereas off-period dystonia often responds to baclofen and botulinum toxin injections. Diphasic dyskinesias, occurring particularly in patients with young-onset PD, are the most difficult to treat. While fractionation of levodopa dosage is the most frequently utilized strategy, many patients require deep brain stimulation to control their troublesome motor fluctuations and LIDs. A variety of emerging (experimental) drugs currently in development promise to provide better control of LIDs and other levodopa-related complications in the near future.

Algorithmic design of a noise-resistant and efficient closed-loop deep brain stimulation system: A computational approach

Advances in the field of closed-loop neuromodulation call for analysis and modeling approaches capable of confronting challenges related to the complex neuronal response to stimulation and the presence of strong internal and measurement noise in neural recordings. Here we elaborate on the algorithmic aspects of a noise-resistant closed-loop subthalamic nucleus deep brain stimulation system for advanced Parkinson’s disease and treatment-refractory obsessive-compulsive disorder, ensuring remarkable performance in terms of both efficiency and selectivity of stimulation, as well as in terms of computational speed. First, we propose an efficient method drawn from dynamical systems theory, for the reliable assessment of significant nonlinear coupling between beta and high-frequency subthalamic neuronal activity, as a biomarker for feedback control. Further, we present a model-based strategy through which optimal parameters of stimulation for minimum energy desynchronizing control of neuronal activity are being identified. The strategy integrates stochastic modeling and derivative-free optimization of neural dynamics based on quadratic modeling. On the basis of numerical simulations, we demonstrate the potential of the presented modeling approach to identify, at a relatively low computational cost, stimulation settings potentially associated with a significantly higher degree of efficiency and selectivity compared with stimulation settings determined post-operatively. Our data reinforce the hypothesis that model-based control strategies are crucial for the design of novel stimulation protocols at the backstage of clinical applications.

New and emerging medical therapies in Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is one of the most challenging neurodegenerative disorders to treat as it manifests with a large variety of troublesome, and often disabling, motor and non-motor symptoms. Despite limitations, such as motor and other complications, levodopa remains the most effective drug in the treatment of PD.

AREAS COVERED

In this review, we focus on phase 2 and 3 studies describing new and emerging medical therapies in PD. We discuss new formulations of levodopa, medications that prolong levodopa response and ameliorate levodopa-induced dyskinesias, and innovative delivery methods that are currently being evaluated in clinical trials or are in development with the promise of better efficacy and tolerability. We also describe novel non-dopaminergic drugs that have been identified for treatment of motor and non-motor symptoms. A specific section is designated for potential disease modifying therapies.

EXPERT OPINION

Alternative formulations of levodopa appear to be promising especially to help with the motor fluctuations either by providing sustained benefits with controlled released formulations or ameliorate sudden OFF by formulations such as inhaled levodopa. Several different medications affecting non-dopaminergic pathways are being evaluated which may aide levodopa. As the understanding of the disease grows further, numerous novel neuroprotective or disease modifying therapies have been suggested. This along with development of medications to treat various non-motor symptoms will help improve quality of life of patients with PD.