Properties and Storage Methods of the Stratathane ST-504-Based Neurosurgical Tumor Model: Comprehensive Analysis.

BACKGROUND: Constrains on neurosurgical residents' work hours demand innovative teaching models to complement the traditional "in the operating room" model. Stratathane ST-504 (Strata-Tech, Inc., Des Moines, Iowa, USA) has been proposed as a useful artificial neurosurgical tumor model. The consistency, dissectability, and radio-opacity of this model strongly depend on its preparation and storage. However, little work has addressed the interplay of these properties. Hence our study was undertaken to explore the properties of ST-504, its preparation, and storage and how these interactions affect its radio-opacity and consistency. METHODS: Tumor mixture was prepared by mixing 4.5 mL of water, 1.5 mL of computed tomography contrast medium, 2 mL of ST-504, and 0.5 mg turmeric powder. The tumor mixture was either allowed to solidify, yielding solid tumor blocks, or injected into an anatomic specimen to create a tumor model. Both tumor blocks and tumor model were stored at different temperature, under different storage conditions and for different time. Their volumes, computed tomography appearance, and consistency were evaluated. RESULTS: The tumor blocks stored in water or ethanol absorbed fluid, resulting in enlargement and associated decrease in radiodensity and consistency. The same results were displayed by the tumor implanted in cadaveric specimen. CONCLUSION: For any given ratio of ST-504/water, the time sequence after polymer solidification and the storage method determine the computed tomography appearance and consistency of the tumor block/model. When taking these properties into consideration, ST-504-based artificial tumor models can be customized for different dissection practices, from more solid (meningioma-like) to less solid (schwannoma-like) models.

Petroclival tumor model--technical note and educational implications.

Petroclival area lesions are rare, and their surgery is challenging due to the deep location and to the complex relationships between the tumor and the neurovascular structures. The objective is to present a petroclival tumor model simulating the distorted anatomy of a real petroclival lesion and propose its use to practice microsurgical removal while preserving neurovascular structures. Four embalmed cadaver heads were used in this study. An endoscopic endonasal transclival approach was used to access the dura in front of the trigeminal nerve; a pediatric Foley was inserted above the trigeminal nerve and was gradually inflated (one-balloon technique). If a larger tumor model was desired, an additional balloon was placed below the trigeminal nerve (two-balloon technique). A pre-mixed tumor polymer was injected into the petroclival space and allowed to harden to create an implanted tumor. A post-implant CT scan was done to evaluate the location and volume of the implanted artificial tumor. Tumors were subsequently excised via retrosigmoid and anterior petrosal approaches. Six petroclival tumors were successfully developed: three were small (9.41-10.36 ml) and three large (21.05-23.99 ml). During dissection, distorted anatomy created by the tumor model mimicked that of real surgery. We have established a petroclival tumor model with adjustable size which offers opportunities to study the distorted anatomy of the area and that is able to be used as a training tool to practice microsurgical removal of petroclival lesions. The practice dissection of this tumor model can be a bridge between a normal anatomic dissection and real surgery.

Maximizing the petroclival region exposure via a suboccipital retrosigmoid approach: where is the intrapetrous internal carotid artery?

BACKGROUND: Recent reports have validated the use of retrosigmoid approach extensions to deal with petroclival lesions. OBJECTIVE: To describe the topographic retrosigmoid anatomy of the intrapetrous internal carotid artery (IICA), providing guidelines for maximizing the petroclival region exposure via this route. METHODS: The IICA was exposed bilaterally in 6 specimens via a retrosigmoid approach in the semisitting position. Its topographic relationship with pertinent posterolateral cranial base landmarks was quantified with neuronavigation. RESULTS: Safe exposure of the IICA and the surrounding inframeatal/petroclival regions was accomplished in all specimens. On average, the IICA genu was 15.08 mm anterolateral to the XI nerve in the jugular foramen, 16.18 mm anteroinferolateral to the endolymphatic sac, and 10.63 mm anteroinferolateral to the internal acoustic meatus. On average, the IICA horizontal segment was 9.92 mm inferolateral to the Meckel cave, and its midpoint was 19.96 mm anterolateral to the XI nerve in the jugular foramen. The mean distance from the IICA genu to the cochlea was 1.96 mm. The genu and the midpoint of the horizontal segment of the IICA were exposed at a depth of approximately 14.50 mm from the posterior pyramidal wall with the use of different drilling angles (49.74° vs 39.54°, respectively). CONCLUSION: Knowledge of the IICA general relationship with these landmarks (combined with a careful assessment of the preoperative imaging and with the use of intraoperative navigation and micro-Doppler) may help to enhance the inframeatal/petroclival region exposure via a retrosigmoid route, maximizing safe inframeatal and suprameatal petrous bone removal while minimizing neurovascular complications.

In vivo brain electrophoresis - a novel method for chemotherapy of CNS diseases.

OBJECTIVE: The blood-brain barrier (BBB) is a protective mechanism that does its job superbly. So much so, that hitherto, brain chemotherapy has been limited by it. In fact, very few agents are effective against brain disease due to the inherent difficulties of penetrating the BBB. We describe a novel, extremely focused method for delivering drugs to specific diseased areas. This innovative method directly delivers putative substances to the pathological area, bypassing the BBB. Treatment of brain diseases could be improved by targeted, controlled delivery of therapeutic substances to diseased cerebral areas. Our described novel method - in vivo electrophoresis - achieves this. METHODS: This technique was evaluated in beagles after craniotomy was performed and a custom-designed plate with electrodes inserted. The delivery of charged substances to selected areas with predictably guided movement was achieved via a created electrical field. Gadolinium, a compound unable to cross the BBB, was injected intracerebrally whereas an electrical field was created using the implanted electrodes surrounding the injection area. The electrical field-guided Gadolinium movement was evaluated using MRI. RESULTS: Gadolinium was moved predictably using the created electrical field without complications. CONCLUSIONS: The experiment successfully demonstrated controlled movement of the substance. This technique can significantly change treatment of brain diseases because substances: i) may be moved in a controlled, predictable way - exponentially increasing therapeutic interactions with the target; and ii) no longer need to conform to constraints dictated by the BBB (molecular mass < 500 d; lipophilic), thereby increasing potential number of usable substances.

A prospective phase II trial of fractionated stereotactic intensity modulated radiotherapy with or without surgery in the treatment of patients with 1 to 3 newly diagnosed symptomatic brain metastases.

BACKGROUND: Several studies have demonstrated that omitting the routine use of adjuvant whole-brain radiation therapy for patients with newly diagnosed brain metastases may be a reasonable first-line strategy. Retrospective evidence suggests that fractionated stereotactic radiotherapy (fSRT) may have a lower level of toxicity with equivalent efficacy in comparison with radiosurgery. OBJECTIVE: To study the phase II efficacy of using a focally directed treatment strategy for symptomatic brain metastases by the use of fSRT with or without surgery and omitting the routine use of adjuvant whole-brain radiation therapy. METHODS: We used a Fleming single-stage design of 40 patients. Patients were eligible if they presented with 1 to 3 newly diagnosed symptomatic brain metastases, Karnofsky performance scale (KPS) greater than 60, and histological confirmation of primary disease. Patients underwent fSRT with the use of a dose of 30 Gy in 5 intensity-modulated fractions as primary or adjuvant treatment after surgical resection. The primary end point was the proportion of patients who experienced neurological death. Secondary end points were overall survival, time to KPS <70, and progression-free survival. RESULTS: Of 40 patients accrued, 39 were eligible for analysis. The proportion of patients dying of neurological causes was 13% (5 patients), which includes 3 patients with an unknown cause of death. Median overall survival, time to KPS <70, and progression-free survival were 16 (95% confidence interval, 9-23), 14 (95% confidence interval, 7-20), and 11 (95% confidence interval, 4-21) months, respectively. CONCLUSION: A focally directed treatment strategy using fSRT with or without surgery appears to be an effective initial strategy. Based on the results of this phase II clinical trial, further study is warranted.

Surgical outcomes using wide suboccipital decompression for adult Chiari I malformation with and without syringomyelia.

Posterior fossa decompression with or without duraplasty is the most common surgical technique employed to treat Chiari-1 malformation (CM). There is considerable debate as to whether large versus small craniectomy leads to better outcomes. The aim of this study was to report our technique and outcomes using a wide suboccipital craniectomy with arachnoid sparing duraplasty. A retrospective review of medical records for symptomatic CM patients with and without syringomyelia was conducted. Follow-up results were obtained via telephone interviews and medical records. Favorable outcome was defined as improvement in self-rated overall status and/or improvement in Glasgow outcome scale (GOS) score. Poor outcome was defined as worsening of either self-rated overall status or GOS score postoperatively. Mean age of 28 female and 2 male patients was 36.6 years (range 20-67). Seven (23%) patients had syringomyelia, one (3%) had hydrocephalus, and two (7%) had prior surgery. Mean follow-up was 27.5 months (range 5-72). Favorable, acceptable, and poor outcomes were achieved in 90%, 3%, and 7% respectively. 87% of respondents indicated they would choose surgery if they had to make a decision again. The most common complication was pseudomeningocele (23%) followed by CSF leak (10%) and meningitis (7%). One transient (3%) neurologic complication occurred. Surgical technique of wide bony decompression of posterior fossa with arachnoid sparing pericranial duraplasty demonstrates favorable outcomes with an acceptable complication rate for patients with symptomatic CM. Prior CM decompression and non-autologous dural graft were associated with poor outcome. Further study is needed to determine the optimal extent of bony decompression.

Hypofractionated intensity modulated radiotherapy with temozolomide in newly diagnosed glioblastoma multiforme.

We conducted a phase I study to determine (a) the maximum tolerated dose of peri-radiation therapy temozolomide (TMZ) and (b) the safety of a selected hypofractionated intensity modulated radiation therapy (HIMRT) regimen in glioblastoma multiforme (GBM) patients. Patients with histological diagnosis of GBM, Karnofsky performance status (KPS)≥ 60 and adequate bone marrow function were eligible for the study. All patients received peri-radiation TMZ; 1 week before the beginning of radiation therapy (RT), 1 week after RT and for 3 weeks during RT. Standard 75 mg/m(2)/day dose was administered to all patients 1 week post-RT. Dose escalation was commenced at level I: 50mg/m(2)/day, level II: 65 mg/m(2)/day and level III: 75 mg/m(2)/day for 4 weeks. HIMRT was delivered at 52.5 Gy in 15 fractions to the contrast enhancing lesion (or surgical cavity) plus the surrounding edema plus a 2 cm margin. Six men and three women with a median age of 67 years (range, 44-81) and a median KPS of 80 (range, 80-90) were enrolled. Three patients were accrued at each TMZ dose level. Median follow-up was 10 months (range, 1-15). Median progression free survival was 3.9 months (95% confidence interval [CI]: 0.9-7.4; range, 0.9-9.9 months) and the overall survival 12.7 months (95% CI: 2.5-17.6; range, 2.5-20.7 months). Time spent in a KPS ≥ 70 was 8.1 months (95% CI: 2.4-15.6; range, 2.4-16 months). No instance of irreversible grade 3 or higher acute toxicity was noted. HIMRT at 52.5 Gy in 15 fractions with peri-RT TMZ at a maximum tolerated dose of 75 mg/m(2)/day for 5 weeks is well tolerated and is able to abate treatment time for these patients.

Recurrent atlantoaxial synovial cyst resection via a navigation-guided, endoscope-assisted posterior approach.

BACKGROUND: Atlantoaxial cysts are rare, and only 46 histologically confirmed cases have been reported. CASE DESCRIPTION: A 75-year-old male presented 2 years ago with headache, neck pain, loss of balance, and episodic dysphagia, for which he had undergone posterior cervical drainage of a left-sided atlantoaxial cyst. Although his original symptoms resolved, they recurred 2 years later and were correlated with an enhanced MR that showed a recurrent left C1-C2 synovial cyst causing marked cervical cord compression. It was successfully resected through a navigation-guided, endoscope-assisted posterior approach. The patient's symptoms/signs resolved completely, and he has remained symptom-free for over 30 months postoperatively, with no evidence of recurrence on MR or craniocervical instability. CONCLUSIONS: A patient who successfully underwent resection of a recurrent synovial cervical cyst using a navigation-guided, endoscope-assisted posterior approach has been reported here.

Successful resection of anterior and anterolateral lesions at the craniovertebral junction using a simple posterolateral approach.

Tumors at the craniovertebral junction (CVJ) often present a challenge due to proximity to vital neurovascular structures. In the last few decades, many authors have proposed complex surgical approaches to access pathologies located anterior or anterolateral to the CVJ with the hopes of reducing morbidity. We propose that the simple posterolateral approach in a semi-sitting position can be used to resect most anterior and anterolateral CVJ tumors safely and effectively. We retrospectively reviewed the clinical series of 10 patients treated by the senior author using the posterolateral suboccipital approach to treat anterior or anterolateral CVJ pathologies. We describe our surgical techniques, outcomes, and present illustrative patients. Gross total resection was achieved in eight patients (80%). Good functional outcome (Glasgow Outcome Scale 4-5) was obtained in all patients. Preoperative symptoms and deficits were improved (78%) or stable (22%) in all patients. There was one (10%) surgical complication that was cerebrospinal fluid leak requiring reoperation. There was no permanent morbidity or mortality in this series. There were two (20%) medical complications including deep vein thrombosis and pulmonary embolus. There were three (30%) transient neurologic complications, dysphagia in two and dysarthria in one, all of which resolved completely in early follow-up. The majority of anterior or anterolateral CVJ lesions can be successfully removed using the simple posterolateral approach.

A streamlined protocol for the use of the semi-sitting position in neurosurgery: a report on 48 consecutive procedures.

The semi-sitting position has lost favor among neurosurgeons partly due to unproven assumptions of increased complications. Many complications have been associated with this position; the most feared: venous air embolism and paradoxical air embolism. We report on this retrospective study of the outcome over 4 years of 48 neurosurgical patients operated on consecutively using a standardized protocol: 41 (85%) in the semi-sitting position, and seven (15%) in the prone position. Procedures included: tumor resection (34), posterior fossa decompression (12), cyst resection (1) and resection of arteriovenous malformation (1). Pre-operative workup was standardized. Vigilant intra-operative observation was done by an experienced neuroanesthetist. Pertinent data was extracted from surgical records. Of the 48 patients, 10 (20.8%) were found to have a patent foramen ovale (PFO) on trans-esophageal echocardiography. Of these, four (40%) patients underwent procedures in the semi-sitting position while six (60%) did not. A clinically significant venous air embolism (VAE) was detected during 2 of the 41 semi-sitting procedures (4.9%). Neither patient suffered any obvious sequelae. No other morbidity was encountered associated with surgical position. Our study suggests that a model similar to ours is effective in preventing major complications associated with the semi-sitting position. The semi-sitting position is a safe, practical position that should be considered in appropriate cases. The fear of dreadful complications seems unwarranted.

Spinal Neurofibroma Masquerading as a Herniated Disc: A case report.

We present the only case in English medical literature of a spinal neurofibroma misdiagnosed as a herniated disc using magnetic resonance imaging (MRI). This case presented with typical symptoms and radiological findings of a herniated disc. Intraoperatively, an abnormality was noted at the S1 nerve root sleeve. Further exploration revealed a spinal neurofibroma which was completely resected, resulting in an improvement in the patient's symptoms. Currently, there is heavy reliance on MRI as a highly sensitive and specific tool used in the diagnosis of herniated lumbar discs. Although there have been occasional reports of misdiagnoses using MRI, there are no reported cases of a spinal neurofibroma being misdiagnosed as a herniated lumbar disc. Despite great advances in radiological diagnostic imaging, surgical surprises do still occur. Ultimately, instinct is still essential in intraoperative surgical decisions.

Path to the Interpeduncular Fossa: Anatomical Comparison of Endoscopic-Assisted versus Standard Subtemporal Approach.

Objective The aim of this study was to assess the assumed advantage of endoscopic assistance to the standard subtemporal approach. The idea was to measure qualitatively and quantitatively visibility versus operability. Design We performed eight subtemporal dissections on four cadaver heads. Our dissections integrated an operating microscope, endoscope, and neuronavigation. Comparison was made between visibility and operability afforded by the microscope alone or by the microscope-endoscope combination. Visibility was recorded as complete or incomplete and was quantified for key structures using linear measurements taken by the navigation system. Operability was determined by whichever maneuvers could be safely and comfortably accomplished in the space afforded. Results From our survey, the structures whose visibility most benefitted from the addition of the endoscope include: contralateral third nerve, posterior perforated substance, mammillary bodies, and contralateral superior cerebellar artery. With regard to quantitative evaluation, we found increased visibility of both basilar artery and posterior cerebral artery. With regard to the operability, no objective advantage was afforded by the addition of the endoscope. Subjectively, the maneuvers were easier to perform while using the endoscope. Conclusion Using the endoscope as an assistance tool during conducting classical subtemporal approach can help in overcome a lot of the classical subtemporal approach limitations.