Insights into Advanced Neurological Dysfunction Mechanisms Following DBS Surgery in Parkinson's Patients: Neuroinflammation and Pyroptosis

Parkinson's disease is a severe neurodegenerative disorder. Currently, deep brain electrical stimulation (DBS) is the first line of surgical treatment. However, serious neurological impairments such as speech disorders, disturbances of consciousness, and depression after surgery limit the efficacy of treatment. In this review, we summarize the recent experimental and clinical studies that have explored the possible causes of neurological deficits after DBS. Furthermore, we tried to identify clues from oxidative stress and pathological changes in patients that could lead to the activation of microglia and astrocytes in DBS surgical injury. Notably, reliable evidence supports the idea that neuroinflammation is caused by microglia and astrocytes, which may contribute to caspase-1 pathway-mediated neuronal pyroptosis. Finally, existing drugs and treatments may partially ameliorate the loss of neurological function in patients following DBS surgery by exerting neuroprotective effects.

Learning Curve Analysis and Adverse Events After Implementation of Neurosurgical Laser Ablation Treatment: A Population-Based Single-Institution Consecutive Series

OBJECTIVE AND METHODS

We conducted a retrospective review of the first 30 patients treated with stereotactic laser ablation (SLA) at our institution since the introduction of the technique in September 2019. We aimed to analyze our initial results and potential learning curve by investigating precision and lesion coverage and assessing the frequency and nature of adverse events according to the Landriel-Ibanez classification for neurosurgical complications.

RESULTS

Indications were de novo gliomas (23%), recurrent gliomas (57%), and epileptogenic foci (20%). There was a trend toward improvement of lesion coverage and target deviation, and a statistically significant improvement in entry point deviation, over time. Four patients (13.3%) experienced a new neurological deficit, where three patients had transient and one patient had permanent deficits, respectively. Our results show a learning curve on precision measures over the first 30 cases. Based on our results the technique can safely be implemented at centers with experience in stereotaxy.

Magnetic resonance-guided laser interstitial thermal therapy for posterior fossa neoplasms

PURPOSE

Magnetic resonance-guided laser interstitial thermal therapy (LITT) has been increasingly used to treat a number of intracranial pathologies, though its use in the posterior fossa has been limited to a few small series. We performed a multi-institutional review of targets in the posterior fossa, reporting the efficacy and safety profile associated with laser ablation in this region of the brain.

METHODS

A retrospective review of patients undergoing LITT in the posterior fossa was performed from August 2010 to March 2020. Patient demographic information was collected alongside the operative parameters and patient outcomes. Reported outcomes included local control of the lesion, postoperative complications, hospital length of stay, and steroid requirements.

RESULTS

58 patients across four institutions underwent LITT in the posterior fossa for 60 tumors. The median pre-ablation tumor volume was 2.24 cm³. 48 patients (50 tumors) were available for follow-up. An 84% (42/50) overall local control rate was achieved at 9.5 months median follow up. There were two procedural complications, including insertional hemorrhage and laser misplacement and 12/58 (21%) patients developed new neurological deficits. There was one procedure related death. The median length of hospital stay was 1 day, with 20.7% of patients requiring discharge to a rehabilitation facility.

CONCLUSIONS

LITT is an effective approach for treating pathology in the posterior fossa. The average target size is smaller than what has been reported in the supratentorial space. Care must be taken to prevent injury to surrounding structures given the close proximity of critical structures in this region.

The intersection between immunotherapy and laser interstitial thermal therapy: a multipronged future of neuro-oncology

The rise of immunotherapy (IT) in oncological treatment has greatly improved outcomes in a number of disease states. However, its use in tumors of the central nervous system (CNS) remains limited for multiple reasons related to the unique immunologic tumor microenvironment. As such, it is valuable to consider the intersection of IT with additional treatment methods that may improve access to the CNS and effectiveness of existing IT modalities. One such combination is the pairing of IT with localized hyperthermia (HT) generated through technologies such as laser interstitial thermal therapy (LITT). The wide-ranging immunomodulatory effects of localized and whole-body HT have been investigated for some time. Hyperthermia has demonstrated immunostimulatory effects at the level of tumor cells, immune cells, and the broader environment governing potential immune surveillance. A thorough understanding of these effects as well as the current and upcoming investigations of such in combination with IT is important in considering the future directions of neuro-oncology.

Radiographic Trends for Infield Recurrence After Radiosurgery for Cerebral Metastases

Objective Recurrence following stereotactic radiosurgery (SRS) for the treatment of cerebral metastases is not uncommon. Recurrence can represent recurrent tumor and/or radiation necrosis. The radiographic response to Gamma Knife (GK) treatment is variable with some remaining stable, some decreasing in size, some increasing in size, while some may show a combination of all three. For tumors that demonstrate progression on MRI, the question to intervene with additional surgical or radiation therapy and the timing of such intervention remains debatable. In this study, we retrospectively reviewed surveillance MRIs of post-GK cerebral metastases to determine if radiographic trends are a predictor of infield progression. Methods A retrospective review of cerebral metastases treated with GK radiosurgery with at least two consecutive post-GK MRI scans was performed. Infield progression was defined by new enhancement increased by at least 25% in two out of three dimensions on two consecutive scans. Primary endpoints for infield recurrence were either continued observation, therapeutic intervention, or withdrawal of care.  Results A total of 579 cerebral metastases were treated with GK radiosurgery. A total of 123 metastases demonstrated radiographic progression on one follow-up MRI scan. Of those, 75% demonstrated continued progression follow-up imaging, while 25% stabilized or regressed. For post-GK metastases demonstrating progression on two consecutive MRI scans, 85% of lesions continued to progress, whereas only 15% demonstrated stabilization or regression. A total of 91% of lesions either require intervention or demonstrate continued progression with observation at this timepoint. Cumulatively 100% of metastases with radiographic progression on ≥3 consecutive MRIs went on to need further intervention. Conclusion Approximately one-fourth of infield recurrence demonstrating progression on the first surveillance MRI will stabilize or regress. Those demonstrating infield progression on two consecutive MRI scans should be considered treatment failures. Early interventions before tumor volume increases in size or patients require high-dose steroids maybe beneficial.

Laser interstitial thermal therapy for in-field recurrence of brain metastasis after stereotactic radiosurgery: does treatment with LITT prevent a neurologic death?

Brain metastasis (BM) affects up to one-third of adults with cancer and carries a historically bleak prognosis. Despite advances in stereotactic radiosurgery (SRS), rates of in-field recurrence (IFR) after SRS range from 10 to 25%. High rates of neurologic death have been reported after SRS failure, particularly for recurrences deep in the brain and surgically inaccessible. Laser interstitial thermal therapy (LITT) is an emerging option in this setting, but its ability to prevent a neurologic death is unknown. In this study, we investigate the causes of death among patients with BM who undergo LITT for IFR after SRS. We conducted a single institution retrospective case series of patients with BM who underwent LITT for IFR after SRS. Clinical and demographic data were collected via chart review. The primary endpoint was cause of death. Between 2010 and 2018, 70 patients with BM underwent LITT for IFR after SRS. Median follow-up after LITT was 12.0 months. At analysis, 49 patients died; a cause was determined in 44. Death was neurologic in 20 patients and non-neurologic in 24. The 24-month cumulative incidence of neurologic and non-neurologic death was 35.1% and 38.6%, respectively. Etiologies of neurologic death included local recurrence (n = 7), recovery failure (n = 7), distant progression (n = 5), and other (n = 1). Among our patient population, LITT provided the ability to stabilize neurologic disease in up to 2/3 of patients. For IFR after SRS, LITT may represent a reasonable treatment strategy for select patients. Additional work is necessary to determine the extent to which LITT can prevent neurologic death after recurrence of BM.

Identification and Management of Progressive Enhancement After Radiation Therapy for Brain Metastases: Results from a Neurosurgical Survey

OBJECTIVE

There is a lack of consensus regarding diagnosis, timing, and method of intervention for progressive enhancement on surveillance imaging after stereotactic radiosurgery (SRS) treatment of brain metastases. We sought to characterize current practices among neurosurgeons in identifying and treating infield tumor recurrence (TR) or radiation necrosis (RN) after SRS for brain metastases.

METHODS

A voluntary survey was distributed electronically to preidentified neurosurgeons. Results were analyzed using descriptive statistics and χ² analysis.

RESULTS

A total of 120 participants completed the survey from 72 U.S. and 17 international centers. Most (69.2%) agreed that growth over ≥2 surveillance scans spaced ≥90 days apart identified irreversible progression after SRS for brain metastases. Respondents were evenly divided on the need for tissue biopsy to distinguish between TR and RN. Preferred treatment modality and time frame to initiate treatment of suspected RN differed among neurosurgeons based on SRS case volume for brain metastases (P = 0.002 and P = 0.02, respectively). Neurosurgeons who used magnetic resonance-guided laser interstitial thermal therapy (LITT) for brain metastases were more likely to prefer LITT for suspected RN, whereas those with minimal LITT experience preferred steroids (P < 0.0001). Neurosurgeons in the United States were more likely to prefer LITT for RN (37.3%) compared with international counterparts (0%).

CONCLUSIONS

Our survey of practicing neurosurgeons highlights areas of controversy in distinguishing between TR and RN and preferred management of suspected RN.

Laser-Induced Thermal Therapy in Neuro-Oncology: A Review

OBJECTIVES

Laser therapy has become an appealing treatment modality in neurosurgery. In this review, we report on the history, physics, surgical steps, indications and uses, and complications that have been reported to date.

METHODS

An extensive literature search was performed for laser interstitial thermal therapy (LITT) and laser therapy in the context of glial tumors, metastatic lesions, pediatric brain tumors, and radiation necrosis. Reported complications in each series also were reviewed.

RESULTS

In the past decade, multiple studies have demonstrated the use, outcomes, and complications associated with LITT in neurosurgery. These same studies have consistently reported an overall benefit of LITT in cases in which traditional surgical approaches may be limited by the patient's clinical status, tumor location, or overall prognosis. However, there have been complications reported from local effects of thermal damage, technical error, and edema development. Increased experience has reduced complications and brought more promising results.

CONCLUSIONS

With the advent of real-time monitoring and damage estimation, LITT has gained ground in the management of intracranial tumors. Larger scale trials must be performed to develop standard protocols to define specific indications for use. Further large clinical studies for LITT in non-oncologic cases are also of interest.

Neurocognitive aspects of brain metastasis

Brain metastases are common, occurring in approximately 20% of cancer patients. One of the biggest concerns for these patients and their families is neurocognitive decline. Neurocognitive issues in this patient population are complex and many patients have neurocognitive impairment due to systemic therapies even before they develop brain metastases. The development of brain metastases as well as the treatment of these tumors can cause decline in neurocognitive function. Diffuse treatments such as whole-brain radiotherapy are more frequently associated with neurocognitive decline than focal interventions such as radiosurgery, surgical resection, and implantable chemotherapy wafers. For patients with brain metastases treatment decisions require a multidisciplinary approach, balancing many factors including the neurocognitive impact of treatment and the disease process itself. Finally, to continue to advance the field there needs to be continued utilization, both off and on clinical trial, of performance-based clinical outcome assessments (i.e., neurocognitive tests) to objectively assess and measure the neurocognitive outcomes of these patients.

Volumetric trends of progressive in-field recurrences after stereotactic radiosurgery of metastatic intracranial tumors

OBJECTIVE

Local recurrence after stereotactic radiosurgery for brain metastasis is a well-known problem. We analyzed volumetric trends from the time of radiosurgery to time of treatment to understand progression behavior.

METHODS

A retrospective review of patients who underwent treatment for post-radiation progressive lesions was performed. Volumetric trends were obtained by plotting individual lesion volumes from the post-radiation nadir volume to volume at treatment and then fitted to exponential decay or linear regressions.

RESULTS

Twenty-eight post-radiation recurrences demonstrated exponential growth and thirteen followed a linear pattern. For lesions exhibiting exponential growth, the average nadir volume was 0.26cm³ (SEM=0.06) at an average of 298 days before treatment and mean volume at treatment was 2.39cm³ (SEM=0.33). The average adjusted R² was 0.94 (SEM=0.013) and doubling factor was 68.60days (SEM=12.55). In the linear growth cohort, the mean nadir volume was 1.43cm³ (SEM=0.25) at an average of 158 days before treatment and average volume at treatment was 6.90cm³ (SEM=1.43). The mean R² was 0.92 (SEM=0.02) and average growth rate was 0.034cm³/day. Majority of lesions from primary non-small cell lung cancer (81%) and breast cancer (63%) followed exponential growth.

CONCLUSIONS

Exponential and linear regressions are accurate representations of post-radiation progression behavior and may be valuable in understanding the growth patterns for recurrences ultimately requiring treatment.