Are patients with GBA-Parkinson disease good candidates for deep brain stimulation? A longitudinal multicentric study on a large Italian cohort

Stress granules: emerging players in neurodegenerative diseases

Stress granules (SGs) are membraneless organelles formed in the cellular cytoplasm under stressful conditions through liquid-liquid phase separation (LLPS). SG assembly can be both dependent and independent of the eIF2α pathway, whereas cellular protein quality control systems mediate SG disassembly. Chaperones and specific domains of RNA-binding proteins strongly contribute to the regulation SG dynamics. Chronic stress, arising in association with aging, may promote persistent SGs that are difficult to disassemble, thereby acting as a potential pathological nidus for protein aggregation in neurodegenerative diseases (NDDs). In this review, we discuss the dynamics of SGs and the factors involved with SG assembly and disassembly. We also highlight the relationship among LLPS, SGs, and the pathogenesis of different NDDs. More importantly, we summarize SG assembly-disassembly, which may be a double-edged sword in the pathophysiology of NDDs. This review aims to provide new insights into the biology and pathology of LLPS, SGs, and NDDs.

LONG-NEXT: A new accurate and efficient NGS-based method for GBA1 analysis in Parkinson disease

INTRODUCTION

GBA1 variants are the most common genetic risk factor for Parkinson disease (PD). Sequencing of GBA1 on a large scale represents a burdensome task with currently adopted diagnostic techniques, namely Sanger sequencing and conventional short read next generation sequencing (sr-NGS). The high degree of sequence homology between GBA1 and its pseudogene GBA1LP is the major driver behind this complexity, leading to false positive and false negative results. We designed, optimized and validated LONG-NEXT, a new NGS-based strategy to streamline large scale GBA1 sequencing.

METHODS

LONG-NEXT relies on a specific long-range PCR, encompassing the whole GBA1 gene, in one fragment (6.5 kb), followed by short-read NGS and a tailored bioinformatic pipeline masking the GBA1LP sequence on the reference genome.

RESULTS

This protocol was optimized and tested on selected cases suspected of diagnostic mistakes by conventional testing (n = 13) and then validated on consecutively collected PD patients already screened either by Sanger sequencing (n = 101) or conventional sr-NGS (n = 294). LONG-NEXT reanalysis of 13 patients disclosed: 3 false positive cases due to mismapping of pseudogene reads on GBA1, 4 false homozygotes due to PCR-related allele dropout events, and 6 false negative cases, due to misalignment of GBA1 reads against the pseudogene or PCR-related allele dropout events. The validation phase disclosed one additional false homozygote in the Sanger cohort, and one false negative result in the sr-NGS cohort.

CONCLUSION

LONG-NEXT is a reliable, fast, cost-effective alternative for GBA1 sequencing and may prove strategic in light of current genotype-based tailored therapies specifically targeting GBA1-PD patients.

Deep brain stimulation in progressive supranuclear palsy: a dead-end story? A narrative review

Progressive supranuclear palsy (PSP) is a rare, debilitating neurodegenerative disorder that significantly impairs both motor and cognitive functions. Current pharmacological treatments offer only transient symptomatic relief, driving interest in the past in alternative therapeutic strategies such as deep brain stimulation. Deep brain stimulation (DBS), known for its success in treating motor symptoms of Parkinson's disease, has been explored as a possible symptomatic treatment for PSP, considering the pedunculopontine nucleus (PPN), involved in motor control and postural stability, as a promising target for deep brain stimulation in PSP. However, its complex anatomy and the clinical variability of PSP complicate the prediction and generalization of the effectiveness of DBS. The present review examines the existing studies in the literature about DBS in PSP patients. Some studies highlighted modest benefits in motor symptoms, while others reported variable outcomes and inherent risks of the procedure. Generally, patients with a parkinsonism predominant phenotype have shown some subjective or clinical improvements in gait and balance when subjected to low-frequency stimulation. While DBS of the PPN holds promise for ameliorating gait and balance of PSP, current evidence does not yet establish clear criteria for ideal candidates, nor does it provide overwhelmingly supportive results in favor of PPN-DBS in PSP patients. Without any further systematic study is not possible to define accurate candidate selection parameters and understand long-term outcomes and safety profiles.

Invasive therapies for Parkinson's disease: an adapted excerpt from the guidelines of the German Society of Neurology

BACKGROUND

Parkinson's disease (PD) is characterized by hypokinetic motor symptoms, tremor, and various non-motor symptoms with frequent fluctuations of symptoms in advanced disease stages. Invasive therapies, such as deep brain stimulation (DBS), ablative therapies, and continuous subcutaneous or intrajejunal delivery of dopaminergic drugs via pump therapies are available for the management of this complex motor symptomatology and may also impact non-motor symptoms. The recent update of the clinical guideline on PD by the German Neurological Society (Deutsche Gesellschaft für Neurologie e.V.; DGN) offers clear guidance on the indications and applications of these treatment options.

METHODS

The guideline committee formulated diagnostic questions for invasive therapies and structured them according to the PICOS framework (Population-Intervention-Comparisons-Outcome-Studies). A systematic literature review was conducted. Questions were addressed using the findings from the literature review and consented by the guideline committee.

RESULTS

Specific recommendations are given regarding (i) the optimal timing for starting invasive therapies, (ii) the application of DBS, (iii) the use of pump therapies in advanced PD, (iv) the indications for ablative procedures, and (iv) selecting the most appropriate therapy according to individual patient characteristics.

CONCLUSION

This review is an adapted excerpt of the chapters on the use of invasive therapies in PD of the novel German guideline on PD. Clear recommendations on the use of treatment options for advanced PD are provided.

Cognitive phenotyping of GBA1-Parkinson's disease: A study on deep brain stimulation outcomes

BACKGROUND

Heterozygous variants in the glucocerebrosidase (GBA1) gene are the most common genetic risk factor for Parkinson's Disease (PD). GBA1-PD patients exhibit earlier disease onset, severe motor impairment, and heightened cognitive decline. Deep Brain Stimulation (DBS) offers motor improvement for PD patients, but its cognitive effects, particularly in GBA1-PD, are debated.

METHODS

This study involved 96 PD patients who underwent subthalamic nucleus DBS at Hospital de la Santa Creu i Sant Pau between 2004 and 2023. Clinical and neuropsychological assessments were conducted pre- and post-surgery, focusing on Mattis Dementia Rating Scale (MDRS) and Frontal Systems Behavior Scale (FrSBe). Patients were categorized into GBA1-PD and non-GBA1-PD groups, with non-GBA1-PD further divided into cognitive fast-progressors and slow-progressors.

RESULTS

GBA1 variants were present in 13.5 % of patients. GBA1-PD patients showed greater cognitive decline over time, particularly in attention, conceptualization, and memory, compared to non-GBA1-PD. Non-GBA1-PD fast-progressors exhibited significant cognitive deterioration in initiation and conceptualization within the first year post-DBS. Motor outcomes improved similarly across all groups, but slow-progressors showed a greater reduction in Levodopa Equivalent Daily Dose (LEDD).

CONCLUSIONS

GBA1-PD patients experience more rapid cognitive decline, particularly in posterior-cortical and fronto-striatal functions. Additionally, a subset of non-GBA1-PD patients shows significant early cognitive decline post-DBS, especially in executive functions. Baseline MDRS scores do not predict cognitive outcomes, highlighting the need for further research to refine prognostic tools. Despite cognitive challenges, GBA1-PD patients benefit from DBS in terms of motor outcomes, underscoring the importance of individualized assessments for DBS suitability, regardless of genetic status.

Advanced therapies in Parkinson's disease: an individualized approach to their indication

Device aided therapies (DAT) comprising the intrajejunal administration of levodopa/carbidopa intestinal gel (LCIG) and levodopa/carbidopa/entacapone intestinal gel (LECIG), the continuous subcutaneous application of foslevodopa/foscarbidopa or apomorphine infusion (CSAI) and deep brain stimulation (DBS) are used to treat Parkinson's disease with insufficient symptom alleviation under intensified pharmacotherapy. These DAT significantly differ in their efficacy profiles, indication, invasiveness, contraindications, and potential side effects. Usually, the evaluation of all these procedures is conducted simultaneously at the same point in time. However, as disease progression and symptom burden is extremely heterogeneous, clinical experience shows that patients reach the individual milestones for a certain therapy at different points in their disease course. Therefore, advocating for an individualized therapy evaluation for each DAT, requiring an ongoing evaluation. This necessitates that, during each consultation, the current symptomatology should be analyzed, and the potential suitability for a DAT be assessed. This work represents a critical interdisciplinary appraisal of these therapies in terms of their individual profiles and compares these DAT regarding contraindications, periprocedural considerations as well as their efficacy regarding motor- and non-motor deficits, supporting a personalized approach.

Multiomics approach discloses lipids and metabolites profiles associated to Parkinson's disease stages and applied therapies

Profiling circulating lipids and metabolites in Parkinson's disease (PD) patients could be useful not only to highlight new pathways affected in PD condition but also to identify sensitive and effective biomarkers for early disease detection and potentially effective therapeutic interventions. In this study we adopted an untargeted omics approach in three groups of patients (No L-Dopa, L-Dopa and DBS) to disclose whether long-term levodopa treatment with or without deep brain stimulation (DBS) could reflect a characteristic lipidomic and metabolomic signature at circulating level. Our findings disclosed a wide up regulation of the majority of differentially regulated lipid species that increase with disease progression and severity. We found a relevant modulation of triacylglycerols and acyl-carnitines, together with an altered profile in adiponectin and leptin, that can differentiate the DBS treated group from the others PD patients. We found a highly significant increase of exosyl ceramides (Hex2Cer) and sphingoid bases (SPB) in PD patients mainly in DBS group (p < 0.0001), which also resulted in a highly accurate diagnostic performance. At metabolomic level, we found a wide dysregulation of pathways involved in the biosynthesis and metabolism of several amino acids. The most interesting finding was the identification of a specific modulation of L-glutamic acid in the three groups of patients. L-glutamate levels increased slightly in No L-Dopa and highly in L-Dopa patients while decreased in DBS, suggesting that DBS therapy might have a beneficial effect on the glutamatergic cascade. All together, these data provide novel insights into the molecular and metabolic alterations underlying PD therapy and might be relevant for PD prediction, diagnosis and treatment.

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

Are LRRK2 p.G2019S or GBA1 variants associated with long-term outcomes of deep brain stimulation for Parkinson's disease?

BACKGROUND

Deep brain stimulation (DBS) is a well-established treatment option for individuals with advanced Parkinson's disease (PD). The potential influence of the LRRK2 p.G2019S or GBA1 variants on its lasting efficacy and adverse effects should be better characterized.

METHODS

We conducted a retrospective single-center case-control study involving PD patients who were carriers of a GBA1 variant (GBA1-PD), the LRRK2 p.G2019S variant (LRRK2-PD), and non-carriers (Nc-PD). All participants underwent DBS and were followed up for at least a year. Assessments before surgery and at 1, 2, 3, 5, and 10 years post-DBS included the following: the Movement Disorder Society's Unified PD Rating Scale (MDS-UPDRS) Part III, Hoehn and Yahr scale, Levodopa Equivalent Daily Dose (LEDD) and non-motor symptoms (psychotic episodes, depressive symptoms, and cognitive decline).

RESULTS

The sample was composed of 103 patients (72 males, mean age at DBS surgery 61.5 ± 8.7 years, mean postoperative follow-up 7.0 ± 4.1 years). Of these, 19 were LRRK2-PD, 20 GBA1-PD, and 64 were Nc-PD. No significant differences in motor outcomes were observed between the groups. Compared to the Nc-PD patients, the GBA1-PD patients were at increased risk of both psychotic episodes [hazard ratio (HR) 2.76 (95 % CI: 1.12-6.80), p = 0.027], and cognitive decline [HR 2.28 (95 % CI: 1.04-5.00), p = 0.04].

CONCLUSION

LRRK2 and GBA1 variant status did not affect the motor outcomes of DBS in PD patients. However, GBA1-PD patients were at increased risk for psychosis and cognitive decline. Further studies are required to determine the role of genetic stratification in referral to DBS.

Longitudinal Neuropsychological Assessment of Symptomatic Edema after Subthalamic Nucleus Deep Brain Stimulation Surgery: A Case Series Study

Severe non-infectious or non-haemorrhagic brain edema surrounding the electrode represents a rare complication of subthalamic nucleus deep brain stimulation (STN-DBS) surgery. The aim of this study is to report three patients with advanced Parkinson's Disease (PD) who developed symptomatic brain edema after STN-DBS surgery treated with intravenous steroids with a specific profile of reversible cognitive alterations. Patients were both assessed with a comprehensive neuropsychological battery including attention, memory, visuo-spatial and executive tasks. They were also briefly assessed for emotional and behavioural alterations, and for possible limitations in the activities of daily living. Normative data for an Italian population were available for all neuropsychological tests. The patients were firstly assessed before the surgery (baseline) as soon as they became symptomatic for the post-surgery edema and a few more times in follow-up up to ten months. In all patients we observed the resolution of cognitive deficits within six months after surgery with the corresponding reabsorption of edema at brain CT scans. The appearance of post-DBS edema is a fairly frequent and clinically benign event. However, in some rare cases it can be very marked and lead to important clinical-albeit transient-disturbances. These events can compromise, at least from a psychological point of view, the delicate path of patients who undergo DBS and can prolong the post-operative hospital stay. In this setting it could be helpful to perform a brain CT scan in 2-3 days with the aim of detecting the early appearance of edema and treating it before it can constitute a relevant clinical problem.