Anatomical Proximity Between Sciatic Nerve and Ischial Spine and its Relationship to the Development of Deep Gluteal Pain Syndrome.

OBJECTIVE: Deep gluteal syndrome (DGS) is a medical diagnosis in which the pathoanatomy of the subgluteal space contributes to pain. The growing recognition that gluteal neuropathies can be associated with the presence of a bone-neural conflict with irritation or compression may allow us to shed some light on this pathology. This study aims to determine whether the location of the sciatic nerve in relation to the ischial spine contributes to the development of DGS. METHODS: The sciatic nerve - ischial spine relationship was analyzed based on magnetic resonance imaging (MRI) in 15 surgical patients who underwent piriformis release, and in 30 control patients who underwent MRI of the pelvis for reasons unrelated to sciatica. The sciatic nerve exit from the greater sciatic foramen was classified as either zone A (medial to the ischial spine); zone B (on the ischial spine); or zone C (lateral to the ischial spine). RESULTS: The sciatic nerve was significantly closer to the ischial spine in surgical patients than in MRI controls (P=0.014). When analyzing patients of similar age, sciatic nerves in surgical patients were significantly closer (P=0.0061) to the ischial spine, and located in zone B significantly more (P=0.0216) as compared to MRI controls. Patients who underwent surgery for piriformis release showed a significant decrease in pain postoperatively (P<0.0001). CONCLUSIONS: The results from this study suggest that the relationship between the ischial spine and sciatic nerve may play a role in the development of DGS. This may also help establish which patients would benefit more from surgical intervention.

Applications of navigation in full-endoscopic spine surgery.

PURPOSE: Advancement in all surgery continues to progress towards more minimally invasive surgical (MIS) approaches. One of the platform technologies which has helped drive this trend within spine surgery is the development of endoscopy; however, the limited anatomic view experienced when performing endoscopic spine surgery requires a significant learning curve. The use of intraoperative navigation has been adapted for endoscopic spine surgery, as this provides computer-reconstructed visual data presented in three dimensions, which can increase feasibility of this technique to more surgeons. METHODS: This paper will describe the principles, technical considerations, and applications of stereotactic navigation-guided endoscopic spine surgery. RESULTS: Full-endoscopic spine surgery has advanced in recent years such that it can be utilized in both decompressive and fusion surgeries. One of the major pitfalls to any minimally invasive surgery (including endoscopic) is that the limited surgical view can often complicate the surgery or confuse the surgeon, leading to longer operative times, higher risks, among others. This is the real utility to using navigation in conjunction with the endoscope-when registered correctly and utilized appropriately, navigated endoscopic spine surgery can take some of the guesswork out of the minimally invasive approach. CONCLUSIONS: Using navigation with endoscopy in spine surgery can potentially expand this technique to surgeons who have yet to master endoscopy as the assistance provided by the navigation can alleviate some of the complexities with anatomic understanding and surgical planning.

Update on Spinal Fusion.

Spinal fusion is frequently performed for a variety of indications. It is performed to treat instability due to trauma, infection, or neoplasm. It may be used to treat regional or global spinal deformity. There are even occasions when it is appropriate as a treatment of low back pain without overt instability or deformity. One common indication for fusion is as an adjunct to decompression for patients with neurogenic claudication or radiculopathy caused by stenosis associated with spondylolisthesis. There have been a number of high-quality publications in high-quality journals that have reported conflicting results regarding the utility of fusion in this patient population. The existence of conflicting data from seemingly similarly designed trials has resulted in some confusion as to when a fusion should be used. This chapter will describe the controversy, discuss the likely basis for the disparate results reported in the literature, and recommend a reasonable treatment strategy. Going forward, the SLIP II study is an ongoing randomized, controlled trial designed to help clarify the situation. Preliminary findings drawn from this study will be discussed.

Hydrocephalus Following Giant Transosseous Vertex Meningioma Resection.

Introduction Meningiomas are among the most common primary intracranial tumors. While well-described, there is limited information on the outcomes and consequences following treatment of giant-sized vertex-based meningiomas. These meningiomas have specific risks and potential complications due to their size, location, and involvement with extracalvarial soft tissue and dural sinuses. Herein, we present four giant-sized vertex transosseous meningioma cases with involvement and occlusion of the sagittal sinus, that postoperatively developed external hydrocephalus and ultimately required shunting. Methods A retrospective chart review identified patients with large vertex meningiomas that were: (1) large (>6 cm) with hemispheric (no skull base) location, (2) involvement of the superior sagittal sinus resulting in complete sinus occlusion, (3) involvement of dura resulting in a large duraplasty area, (4) transosseous involvement requiring a 5 cm or larger craniectomy for resection of invaded calvarial bone. Results Tumors were resected in all four cases, with all patients subsequently developing external hydrocephalus which required shunting within 2 weeks to 6 months postsurgery. Conclusion We believe this may be the first report of the development of hydrocephalus following surgical resection of these large lesions. Based on our observations, we propose that a combination of superior sagittal sinus occlusion and changes in brain elasticity and compliance affect the brain's CSF absorptive capacity, which ultimately lead to hydrocephalus development. We suggest that neurosurgeons be aware that postoperative hydrocephalus can quickly develop following treatment of giant-sized vertex-based meningiomas, and that correction of hydrocephalus with shunting can readily be achieved.

Upper Thoracic Spine Synovial Cyst Resulting in Paraplegia Following Transient Hypotension.

Development of synovial cysts in the rigid thoracic spine is rare. Additionally, synovial cysts with compression of nerve roots typically cause subacute or chronic radiculopathy. We present a patient who had a new diagnosis of upper thoracic (T1-2) synovial cyst that caused acute paraplegia while hospitalized for therapies and surgical planning. The patient is a 56-year-old male with a history of congestive heart failure secondary to alcoholic cardiomyopathy. He presented with a progressive bilateral lower extremity discoordination, urinary incontinence, and altered perineal sensation. His examination revealed intact strength to bedside assessment, intact rectal tone, but upgoing toes on Babinski testing. Given concern for myelopathy, MRI thoracic spine was obtained and demonstrated large T1-2 synovial cyst causing severe compression with associated T2 signal change within the spinal cord. He underwent expedited cardiac optimization that included resumption of outpatient antihypertensive medications and the addition of a single dose of intravenous diuretic. The patient had subsequent transient hypotension following significant diuresis and developed acute paraplegia in his bilateral lower extremities. Fluids and vasopressors were initiated, and he underwent emergent surgery for decompression and synovial cyst resection. The patient did very well and had normalization of his neurological exam within 24 hours. We present a case of acute paraplegia secondary to hypotension and spinal cord hypoperfusion in a patient with upper thoracic synovial cyst. This is rare pathology with an even more unique presentation. The authors recommend careful perioperative hemodynamic monitoring to help avoid acute worsening in this patient population.

Interobserver variance and patient heterogeneity influencing the treatment of grade I spondylolisthesis.

BACKGROUND CONTEXT: Despite well done randomized clinical trials, the role of fusion as an adjunct to decompression for the treatment of patients with degenerative spondylolisthesis remains controversial. There is substantial variation in the use of fusion as well as the techniques used for fusion for a population of patients all described by a single ICD10 code. PURPOSE: We sought to investigate the source of the variation in the perceived role of fusion by looking at surgeon as well as patient-specific factors. STUDY DESIGN: Prospective cohort study examining the variability of recommendations from an expert panel of surgeons-based imaging and clinical vignettes. PATIENT SAMPLE: Patients with degenerative spondylolisthesis and stenosis. OUTCOME MEASURES: A six-category treatment schema based on level of invasiveness of proposed surgeries with one through three representing nonfusion strategies and categories four through six representing fusion strategies. METHODS: The authors are conducting the ongoing spinal laminectomy vs instrumented pedicle screw II study in which patients with grade one degenerative spondylolisthesis and stenosis are randomized to two groups: a review group in which patients are treated as per recommendations of an expert panel and a nonreview group in which patients are treated as per the referring surgeon's preference. In the former (review group), clinical vignettes and radiographic studies were evaluated by an expert panel of spine surgeons. The panel then provided these recommendations to the referring surgeon. We investigated the underlying variability by looking both at the number of similar or different recommendations received by an individual patient (surgeon-related variability) as well as the number of similar or different recommendations offered by individual surgeons across the population of patients (patient heterogeneity). Agreement between surgeons for fusion vs nonfusion (Categories 1-3 vs 4-6) was calculated using a Kappa value from a mixed effects logistic regression model. We looked at Kappa for agreement and weighted Kappa for association of ratings on the ordinal 1 to 6 scale with a mixed effects linear regression model. Additionally, we analyzed the summary of data between patients after averaging the rater scores within patients. Similarly, we summarized the data between surgeons after averaging their scores over the patients that each surgeon reviewed. RESULTS: One hundred and fourteen patients received 1,463 treatment recommendations. On average, fusion was recommended 58.5% of the time. Overall agreement was low, and perfect agreement on the need for fusion was seen in only 24 (21.1%) of patients. Kappa statistic for agreement on fusion was 0.378 (95% confidence interval 0.324-0.432). The average score across surgeons was 4.2 (0.6) with a range of 3 to 5.3. The most common single recommendation was for fusion with interbody fusion (40.8%) and the lowest was for decompression with noninstrumented fusion (0.5%). CONCLUSIONS: We demonstrated variability in surgical approach when individual patients were evaluated by a panel of surgeons indicating that even "expert" surgeons disagree with each other regarding the need for fusion in individual patients. We were also able to demonstrate that individual patients received consistent recommendations that were very different from those received by other individuals evaluated by the same surgeons. This indicates that there is patient-related heterogeneity driving variability independent of surgeon factors.

Deadly Proliferation and Transformation of Pilocytic Astrocytoma in Pregnancy.

BACKGROUND: Intracranial tumor growth associated with pregnancy is not an uncommon phenomenon. Pilocytic astrocytoma is typically considered to be an indolent tumor with little to no risk of progression to higher-grade lesion. We present a rare case of cerebellar pilocytic astrocytoma transformation to hemorrhagic high-grade glioma during pregnancy. CASE DESCRIPTION: Patient EK was a 32-year-old female with neurofibromatosis type 1 and known cerebellar pilocytic astrocytoma. For nearly a decade before her pregnancy, her cerebellar tumor was stable on imaging. Routine magnetic resonance imaging (MRI) of the head obtained at 20 weeks' gestation continued to demonstrate tumor stability. At 24 weeks' gestation, the patient had sudden, severe headaches. MRI of the head showed evidence of significant tumor expansion. The following day, the patient was found unresponsive. Computed tomography of the head demonstrated hemorrhage within the tumor and tonsillar herniation. Her neurologic examination revealed no brainstem reflexes; however, given her age and pregnancy, she underwent emergent decompression and tumor debulking. Unfortunately, she never improved neurologically. Final pathology identified the lesion as high-grade glioma with anaplastic changes and hemorrhagic conversion. CONCLUSIONS: This is a unique case of indolent cerebellar pilocytic astrocytoma that transformed to high-grade glioma during pregnancy, proven by tumor growth on MRI and anaplasia on pathology. We hypothesize that increased levels of pregnancy hormones (progesterone, vascular endothelial growth factor, placental growth factor, among others) likely contributed to tumor growth. We recommend that all glial tumors be monitored extremely closely throughout pregnancy, and perhaps one should consider surgical treatment (if possible) before patients become pregnant.

Computed Tomography Guidance for Percutaneous Glycerol Rhizotomy for Trigeminal Neuralgia.

BACKGROUND: Percutaneous glycerol rhizotomy (PGR) is a well-described treatment for trigeminal neuralgia; however, the technique in using surface landmarks and fluoroscopy has not drastically changed since being first introduced. In this paper, we describe a protocol for PGR using computed tomography (CT) guidance based on an experience of over 7 yr and 200 patients. OBJECTIVE: To introduce an approach for PGR using CT guidance and, in doing so, demonstrate possible benefits over the traditional fluoroscopic technique. METHODS: Using a standard CT scanner, patients are placed supine with head in extension. Barium paste and a CT scout image are used to identify and plan a trajectory to the foramen ovale. A laser localization system built into the CT scanner helps to guide placement of the spinal needle into the foramen ovale. The needle position in the foramen is confirmed with a short-sequence CT scan. RESULTS: CT-guided PGR provides multiple benefits over standard fluoroscopy, including improved visualization of the skull base and significant reduction in radiation exposure to the surgeon and staff. Side benefits include improved procedure efficiency, definitive imaging evidence of correct needle placement, and potentially increased patient safety. We have had no significant complications in over 200 patients. CONCLUSION: CT-guided PGR is a useful technique for treating trigeminal neuralgia based on better imaging of the skull base, better efficiency of the procedure, and elimination of radiation exposure for the surgeon and staff compared to traditional fluoroscopic based techniques.

Use of a Laryngeal Mask Airway Decreases Radiation Exposure During Computed Tomography-Guided Percutaneous Glycerol Rhizotomy for Trigeminal Neuralgia.

BACKGROUND: We have been using computed tomography (CT) guidance for percutaneous glycerol rhizotomy (PGR) for the last 7 years. As a quality improvement exercise, we recently began using general anesthesia (GA) with the use of a laryngeal mask airway (LMA) because of our perception that the procedure went faster and that there was less radiation exposure because of less patient movement. We aim to compare PGR radiation exposure and procedural time between patients receiving local anesthetic with sedation and those receiving GA/LMA. METHODS: A single-center historical cohort study was performed using patients treated with PGR between 2017 and 2019. Ninety-two surgeries were conducted during the study period: 64 surgeries had local anesthetic with intravenous sedation, and 28 surgeries had deeper anesthetic with LMA. Data analyzed included the number of CT sequences obtained, needle placement time, and total radiation dose. RESULTS: Use of GA/LMA resulted in a 23% decrease in mean radiation dose (565.5 vs. 436.1 µGy × cm, P = 0.014), number of CT sequences required (7.4 vs. 5.7, P = 0.003), and needle placement time (12.8 vs. 9.8 minutes, P = 0.006). Additionally, 10 patients underwent multiple glycerol rhizotomies during the collection period with both anesthetic types being used at least once. Seven of 10 patients (70.0%) had a reduction in total radiation dose, number of CT sequences obtained, and needle placement time when GA/LMA was used. There were no procedure- or anesthetic-related complications in this patient cohort. CONCLUSIONS: The use of GA/LMA during PGR is associated with decreased radiation exposure without increased anesthetic complications.

In vivo imaging of ligand receptor binding with Gaussia luciferase complementation.

Studies of ligand-receptor binding and the development of receptor antagonists would benefit greatly from imaging techniques that translate directly from cell-based assays to living animals. We used Gaussia luciferase protein fragment complementation to quantify the binding of chemokine (C-X-C motif) ligand 12 (CXCL12) to chemokine (C-X-C motif) receptor 4 (CXCR4) and CXCR7. Studies established that small-molecule inhibitors of CXCR4 or CXCR7 specifically blocked CXCL12 binding in cell-based assays and revealed differences in kinetics of inhibiting chemokine binding to each receptor. Bioluminescence imaging showed CXCL12-CXCR7 binding in primary and metastatic tumors in a mouse model of breast cancer. We used this imaging technique to quantify drug-mediated inhibition of CXCL12-CXCR4 binding in living mice. We expect this imaging technology to advance research in areas such as ligand-receptor interactions and the development of new therapeutic agents in cell-based assays and small animals.

Noninvasive imaging reveals inhibition of ovarian cancer by targeting CXCL12-CXCR4.

Patients with metastatic ovarian cancer continue to have a dismal prognosis, emphasizing the need for new strategies to identify and develop new molecular targets for therapy. Chemokine CXCL12 and its receptor CXCR4 are upregulated in metastatic ovarian cancer cells and the intraperitoneal tumor microenvironment. CXCL12-CXCR4 signaling promotes multiple steps in proliferation and dissemination of ovarian cancer cells, suggesting that targeted inhibition of this pathway will limit tumor progression. To investigate CXCL12-CXCR4 signaling in ovarian cancer and establish effects of inhibiting this pathway on tumor progression and survival, we designed a Gaussia luciferase complementation imaging reporter system to detect CXCL12 binding to CXCR4 in ovarian cancer cells. In cell-based assays, we established that the complementation imaging reporter could detect CXCL12 binding to CXCR4 and quantify specific inhibition of ligand-receptor interaction. We monitored CXCL12-CXCR4 binding and inhibition in a mouse xenograft model of metastatic human ovarian cancer by imaging Gaussia luciferase complementation and assessed tumor progression with firefly luciferase. Bioluminescence imaging studies in living mice showed that treatment with AMD3100, a clinically approved inhibitor of CXCL12-CXCR4, blocked ligand-receptor binding and reduced growth of ovarian cancer cells. Treatment with AMD3100 also modestly improved overall survival of mice with metastatic ovarian cancer. The Gaussia luciferase complementation imaging reporter system will facilitate further preclinical development and optimization of CXCL12-CXCR4 targeted compounds for treatment of ovarian cancer. Our research supports clinical translation of existing CXCR4 inhibitors for molecular therapy for ovarian cancer.

Near-infrared fluorescent proteins.

Fluorescent proteins with emission wavelengths in the near-infrared and infrared range are in high demand for whole-body imaging techniques. Here we report near-infrared dimeric fluorescent proteins eqFP650 and eqFP670. To our knowledge, eqFP650 is the brightest fluorescent protein with emission maximum above 635 nm, and eqFP670 displays the most red-shifted emission maximum and high photostability.