Operative and Therapeutic Advancements in Breast Cancer Metastases to the Brain

Patients with breast cancer are surviving longer as the state of the art for care advances. Because patients are surviving longer with primary breast cancer, the incidence of secondary metastatic disease has risen. Metastatic breast cancer to the brain was once thought to be universally fatal. While it is still quite lethal, its treatment after diagnosis is increasingly safe and effective. Critical progress has been made in understanding the interaction between breast metastases and the neural niche, neuroimaging of functional anatomy, minimally invasive image-guided brain surgery, characterizing subtypes of breast cancer based on molecular and genetic profiles, and individualized pharmaceuticals and immunotherapies. In this review, we discuss recent advances that have brought us to state-of-the-art management of metastatic breast cancer to the brain.

Robot-assisted endoscopic third ventriculostomy: institutional experience in 9 patients

OBJECTIVE The endoscopic third ventriculostomy (ETV) is an established and effective treatment for obstructive hydrocephalus. In its most common application, surgeons plan their entry point and the endoscope trajectory for the procedure based on anatomical landmarks, then control the endoscope freehand. Recent studies report an incidence of neural injuries as high as 16.6% of all ETVs performed in North America. The authors have introduced the ROSA system to their ETV procedure to stereotactically optimize endoscope trajectories, to reduce risk of traction on neural structures by the endoscope, and to provide a stable mechanical holder of the endoscope. Here, they present their series in which the ROSA system was used for ETVs. METHODS At the authors' institution, they performed ETVs with the ROSA system in 9 consecutive patients within an 8-month period. Patients had to have a favorable expected response to ETV (ETV Success Score ≥ 70) with no additional endoscopic procedures (e.g., choroid plexus cauterization, septum pellucidum fenestration). The modality of image registration (CT, MRI, surface mapping, or bone fiducials) was dependent on the case. RESULTS Nine pediatric patients with an age range of 1.5 to 16 years, 4 girls and 5 boys, with ETV Success Scores ranging from 70 to 90, underwent successful ETV surgery with the ROSA system within an 8-month period. Their intracranial pathologies included tectal tumors (n = 3), communicating hydrocephalus from hemorrhage or meningeal disease (n = 2), congenital aqueductal stenosis (n = 1), compressive porencephalic cyst (n = 1), Chiari I malformation (n = 1), and pineal region mass (n = 1). Robotic assistance was limited to the ventricular access in the first 2 procedures, but was used for the entirety of the procedure for the following 7 cases. Four of these cases were combined with another procedural objective (3 stereotactic tectal mass biopsies, 1 Chiari decompression). A learning curve was observed with each subsequent surgery as registration and surgical times became shorter and more efficient. All patients had complete resolution of their preprocedural symptoms. There were no complications. CONCLUSIONS The ROSA system provides a stable, precise, and minimally invasive approach to ETVs.

Impact of ventricular-peritoneal shunt valve design on clinical outcome of pediatric patients with hydrocephalus: Lessons learned from randomized controlled trials

Hydrocephalus is one of the most common diseases managed by pediatric neurosurgeons. Cerebrospinal fluid (CSF) shunting has been the mainstay of durable treatment for hydrocephalus for many decades. There are two main categories of shunt designs for regulating the extent of CSF diversion: (1) Fixed-parameter valves and (2) adjustable valves. Furthermore, these valves can also function with and without an anti-siphon device. Here, we review randomized controlled trials (RCTs) that examined the impact of these valve designs on the clinical outcome of pediatric patients afflicted with hydrocephalus. All three RCTs suggested no significant differences in clinical outcome as a function of shunt design. Implications of these findings are discussed.

Do corticosteroids play a role in the management of traumatic brain injury?

Neuroprotective strategies for the medical management of traumatic brain injury (TBI) have been elusive. While laboratory studies provide a conceptual framework for the potential efficacy of corticosteroids in this context, clinical trials testing this hypothesis have yielded no convincing evidence of clinical benefit. Here, we review the five key randomized control trials (RCTs) that have examined this issue. Based on the proposed primary endpoints of these RCTs, the five RCTs consistently showed that corticosteroids do not confer significant benefit in the TBI population.

A Novel, Minimally-Invasive Approach to Repair Degenerative Disk Disease in an Ovine Model Using Injectable Polymethyl-Methacrylate and Bovine Collagen (PMMA/BC)

BACKGROUND

The natural, inflammatory repair processes of an injured intervertebral degenerative disc can propagate further injury and destruction. While there are many different treatment modalities of the pain related to degenerative disc disease, none are actually reparative in nature. Treatment strategies to repair a degenerative disc without inducing a destructive inflammatory milieu have been elusive. 

PURPOSE

The purpose of this experiment is to discover the feasibility of reconstructing an injured intervertebral disc using an injected, inert polymer as the foundation for endogenous collagen growth.

STUDY DESIGN

In this ovine model of six subjects in total, we introduce a modality where a large inert polymer, polymethyl methacrylate (PMMA), in conjunction bovine collagen (BC) is injected into the intervertebral disc. Following six months of observation, histologic specimens were evaluated macroscopically and microscopically for evidence of a benefit of the injectable PMMA/BC.

METHODS

We obtained six merino sheep for this study. Concentric injuries were made to four of their lumbar intervertebral discs. Two of those levels were treated with a percutaneous injection of 0.3 cc of PMMA/BC. The remaining lumbar levels were left untreated and were our controls. After six months, all subjects were sacrificed. Their four levels were extracted and were examined macroscopically and microscopically.

RESULTS

All subjects tolerated the lumbar injury and percutaneous injection of PMMA/BC well. After the six month interval, all subjects have demonstrated an intact architecture of their lumbar disc height at the macroscopic and microscopic level. Microscopically, there was no evidence of external migration of the PMMA/BC microspheres, nor was there any evidence of an inflammatory response by its presence. Notably, the PMMA/BC microspheres were well-incorporated into the concentric disc tears and had undergone endogenous collagen formation in its environment. Treatment levels were revealing for maintenance of disc height without evidence of an ongoing degeneration. The controlled levels were revealing for continued disc degeneration with loss of disc height and evolving injury at the level of the concentric tear.

CONCLUSIONS

This ovine model demonstrates a novel and promising technique for prevention and arrest of lumbar intervertebral disc degeneration.

Novel Transabdominal Motor Action Potential (TaMAP) Neuromonitoring System for Spinal Surgery

INTRODUCTION

Minimally invasive lateral lumbar interbody fusion (LLIF) approaches to the lumbar spine reduce patient morbidity compared to anterior or posterior alternatives. This approach, however, decreases direct anatomical visualization, creating the need for highly sensitive and specific neurophysiological monitoring. We seek to determine feasibility in 'transabdominal motor action potential (TaMAP)' monitoring as an assessment for the integrity of the neural elements during lateral-approach surgeries to the lumbar spine.

METHODS

Cathode and anode leads were placed on the posterior and anterior surfaces of two porcine subjects. Currents of varying degrees were transmitted across, from front to back. Motor responses were monitored and recorded by needle electrodes in specific distal muscle groups of the lower extremity. Lastly, the cathode and anode were placed anterior and posterior to the chest wall and stimulated to the maximum of 1500 mA to determine any effect on cardiac rhythm.

RESULTS

Responses were seen by measuring vertical height differences between peaks of corresponding evoked potentials. Recruitment began at 200 mA in the lower extremities. Stimulation at 450 mA recruited a reliable and distinguishable electrographic response from most muscle groups. Responses were recorded and reliably measured and increased in proportion to the graduation of transabdominal stimulation current; no responses were seen in the arms or face. 1500 mA across the chest wall failed to stimulate or induce cardiac arrhythmia on repeated stimulation, indicating safety of stimulation.

CONCLUSION

TaMAPs seen in the animal model provide a potential alternative to standard transcranial motor evoked potentials done in the lateral approach of LLIFs. TaMAP recordings in most muscle groups were recordable and reliable, though some muscle groups failed to stimulate. Safety of transabdominal motor evoked potentials was confirmed in this porcine study. Future studies should examine TaMAPs reliability in detecting compressive lesions of nerve roots and peripheral nerves.

Cadaveric Analysis of the Kambin's Triangle

Introduction

Kambin’s Triangle is a right triangle over the dorsolateral disc. The area of this right triangle currently serves as a strategic site of posterolateral, minimally invasive access to the nerve root for delivery of epidural steroid injections. This posterolateral approach has also been considered a safe area of access to the intervertebral disc space and, thus, an effective approach in reducing complications, such as violation of the thecal sac, the nerve root, or the bony elements of the spine during minimally invasive spinal surgery. No published studies have been performed to characterize the dimensions of the Kambin's Triangle. Our aim is to characterize its dimensions at the lumbar levels and determine its efficacy and safety as a site of access for minimally invasive spinal surgery.

Methods

Two randomly chosen adult male cadavers were used for this study. The measurements were made bilaterally at their lumbar levels (L1–L5), which equates to 16 total measurements (eight bilateral disc spaces on two cadavers). The disc space was first accessed using a Kirschner wire in a standard oblique approach. With the assistance of fluoroscopy, a Kirschner wire was passed into the disc through the Kambin’s Triangle. The procedure was performed on the cadavers bilaterally at four levels, followed by open dissection. The calculations of the area were made by measuring the exiting nerve root, the superior border of the caudal vertebra, and the superior articulating facet—the borders of the Kambin's Triangle.

Results

The Kambin’s Triangle height and width respectively averaged at 12 mm and 10 mm (L1–L2), 13 mm and 11 mm (L2–L3), 17 mm and 11 mm (L3–L4), and 18 mm and 12 mm (L4–L5). Thus, the area at each level was 60 mm² (L1–L2), 71.5 mm² (L2–L3), 93.5 mm² (L3–L4), and 108 mm² (L4–L5). All dissected levels demonstrated adequate anchoring of the Kirschner wire into the disc space with no evidence of nerve injury. Following this, a retractor was placed and complete discectomies were performed. All exiting nerves were protected in this safe zone and the thecal sac remained inviolate.

Conclusion

Understanding the Kambin’s Triangle will assist surgeons in the minimally invasive approach to spinal surgeries, with potentially safe placement of interbody cages through this strategic space.