Microsurgical Anatomy of the Common Tendinous Ring and Its Surgical Implications.

BACKGROUND AND OBJECTIVES: The common tendinous ring (CTR), also known as the common annular tendon or annulus of Zinn, is a critical anatomic structure located at the convergence of the orbital apex, superior orbital fissure (SOF), optic canal, and the anterior aspect of the lateral sellar compartment. It plays a vital role in both neurosurgical and neuro-ophthalmological interventions. The aim of this study was to delineate the complex 3-dimensional (3D) topography of the CTR and explore its implications for surgical procedures. METHODS: Ten formalin-fixed skull base specimens from adult Chinese cadavers were meticulously dissected to investigate the morphology of the CTR, focusing particularly on its relationship with the 4 extraocular rectus tendons, the optic strut, the SOF, and the optic canal. Additional skull base specimens were subjected to 3D surface scanning, computed tomography, and histopathological examinations to deepen our understanding of the CTR's structural complexities. RESULTS: The CTR establishes a spatial, 3D tendinous assembly, encompassing 4 rectus tendons, 2 tendinous connections, and a singular common tendinous root. These components interlink to form a distinctive dual-ring configuration, featuring the optic foramen and the oculomotor foramen. The posterior part of the superior rectus tendon demarcates the common boundary between these 2 foramina. The oculomotor foramen itself serves as the central sector of the SOF. Precise incisions of the medial and lateral tendinous connections and fusions are essential for safely opening the CTR. CONCLUSION: The structural composition, interconnections, and dual-ring configuration of the CTR are crucial for precise and safe surgery of orbital apex and adjacent regions.

Endoscopic Approach to Remove Intra-extracranial Tumors in Various Skull Base Regions: 10-year Experience of a Single Center.

BACKGROUND: Some problems have been found in the usually adopted combined approach for the removal of intra-extracranial tumors in skull base. Herein, we described a pure endoscopic transnasal or transoral approach (ETA) for the removal of intra-extracranial tumors in various skull base regions. METHODS: Retrospectively, clinical data, major surgical complications, pre- and postoperative images, and follow-up information of a series of 85 patients with intra-extracranial tumors in various skull base regions who were treated by surgery via ETA in our skull base center during the past 10 years were reviewed and analyzed. RESULTS: Gross total tumor removal was achieved in 80/85 cases (94.1%) in this study. All 37 cases with tumors in anterior skull base and all 14 cases with tumors in jugular foramen received total tumor removal. Thirteen and three cases with tumors in clivus received total and subtotal tumor removal, respectively. Total and subtotal tumor removal was performed for 16 cases and 2 cases in lateral skull base, respectively. The complications in this study included: cerebrospinal fluid leakage (n = 3), meningitis (n = 3), and new cranial nerve deficits (n = 3; recovered in 3 months after surgery). In the follow-up period of 40-151 months (median: 77 months), seven patients (8.8%) out of the 80 cases of total tumor removal experienced recurrence. CONCLUSIONS: Complete resection of intra-extracranial growing tumors in various skull base regions can be achieved via the pure ETA in one stage in selected cases. Surgical procedure for radical removal of tumors is feasible and safe.

Usefulness of intraoperative electromyographic monitoring of oculomotor and abducens nerves during skull base surgery.

BACKGROUND: Intraoperative neurophysiologic monitoring of the extraocular cranial nerve (EOCN) is not commonly performed because of technical difficulty and risk, reliability of the result and predictability of the postoperative function of the EOCN. METHODS: We performed oculomotor nerve (CN III) and abducens nerve (CN VI) intraoperative monitoring in patients with skull base surgery by recording the spontaneous muscle activity (SMA) and compound muscle action potential (CMAP). Two types of needle electrodes of different length were percutaneously inserted into the extraocular muscles with the free-hand technique. We studied the relationships between the SMA and CMAP and postoperative function of CN III and CN VI. RESULTS: A total of 23 patients were included. Nineteen oculomotor nerves and 22 abducens nerves were monitored during surgery, respectively. Neurotonic discharge had a positive predictive value of less than 50% and negative predictive value of more than 80% for postoperative CN III and CN VI dysfunction. The latency of patients with postoperative CN III dysfunction was 2.79 ± 0.13 ms, longer than that with intact CN III function (1.73 ± 0.11 ms). One patient had transient CN VI dysfunction, whose CMAP latency (2.54 ms) was longer than that of intact CN VI function (2.11 ± 0.38 ms). There was no statistically significant difference between patients with paresis and with intact function. CONCLUSIONS: The method of intraoperative monitoring of EOCNs described here is safe and useful to record responses of SMA and CMAP. Neurotonic discharge seems to have limited value in predicting the postoperative function of CN III and CN VI. The onset latency of CMAP longer than 2.5 ms after tumor removal is probably relevant to postoperative CN III and CN VI dysfunction. However, a definite quantitative relationship has not been found between the amplitude and stimulation intensity of CMAP and the postoperative outcome of CN III and CN VI.

Neuronavigation Based on Track Density Image Extracted from Deterministic High-Definition Fiber Tractography.

BACKGROUND: Diffusion tensor imaging-based navigation is unable to resolve crossing fibers or to determine with accuracy the fanning, origin, and termination of fibers. It is important to improve the accuracy of localizing white matter fibers for improved surgical approaches. We propose a solution to this problem using navigation based on track density imaging extracted from high-definition fiber tractography (HDFT). CASE DESCRIPTION: A 28-year-old asymptomatic female patient with a left-lateral ventricle meningioma was enrolled in the present study. Language and visual tests, magnetic resonance imaging findings, both preoperative and postoperative HDFT, and the intraoperative navigation and surgery process are presented. Track density images were extracted from tracts derived using full q-space (514 directions) diffusion spectrum imaging (DSI) and integrated into a neuronavigation system. Navigation accuracy was verified via intraoperative records and postoperative DSI tractography, as well as a functional examination. DSI successfully represented the shape and range of the Meyer loop and arcuate fasciculus. Extracted track density images from the DSI were successfully integrated into the navigation system. The relationship between the operation channel and surrounding tracts was consistent with the postoperative findings, and the patient was functionally intact after the surgery. CONCLUSIONS: DSI-based TDI navigation allows for the visualization of anatomic features such as fanning and angling and helps to identify the range of a given tract. Moreover, our results show that our HDFT navigation method is a promising technique that preserves neural function.

Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography: a technical note and report of 3 cases.

BACKGROUND: There are no large series studies identifying the locations of cranial nerves (CNs) around trigeminal schwannomas (TSs); however, surgically induced cranial neuropathies are commonly observed after surgeries to remove TSs. In this study, we preoperatively identified the location of CNs near TSs using diffusion tensor tractography (DTT). METHODS: An observational study of the DTT results and intraoperative findings was performed. We preoperatively completed tractography from images of patients with TSs who received surgical therapy. The result was later validated during tumorectomy. RESULTS: A total of three consecutive patients were involved in this study. The locations of CNs V-VIII in relation to the tumor was clearly revealed in all cases, except for CN VI in case 3.The predicted fiber tracts were in agreement with intraoperative observations. CONCLUSIONS: In this study, preoperative DTT accurately predicted the location of the majority of the nerves of interest. This technique can be applied by surgeons to preoperatively visualize nerve arrangements.

Identification of cranial nerves near large vestibular schwannomas using superselective diffusion tensor tractography: experience with 23 cases.

BACKGROUND: The preservation of the facial nerve (FN) and acoustic function in large vestibular schwannoma (VS) surgery is challenging because of nerve course uncertainties and morphological deviations. Preoperative diffusion tensor tractography (DTT) has been proposed to predict the FN location. This study was conducted to evaluate the effectiveness of this technique for identifying the FN, cochlear nerve (CN) and trigeminal nerve (TN) in large VSs. METHODS: The study included 23 consecutive patients with VS of Hannover classification T3b to T4b from November 2013 through May 2014. Diffusion tensor images and anatomical images were acquired. The DTT images of the cranial nerves were extracted before surgery for each patient to determine the relationships of these nerves with the tumor. The results were then validated during the tumorectomy. RESULTS: In 21 (91.30%) patients, the location of the FN on the DTT images agreed with the intraoperative findings, including in 2 patients in whom the FN passed through the interface between the parenchyma and the cystic changes and in 3 patients with a membranoid FN. The CN or fibers of unclear function were observed on DTT images in four patients with functional hearing. One penetrating fiber of unknown function was effectively constructed. The TN was accurately detected on the DTT images for all patients. CONCLUSIONS: DTT effectively revealed the location of the FN, including cases in which the FN was membranoid or passed through the interface between an area exhibiting cystic changes and the tumor nodule. Fibers aside from the FN and the TN were revealed by DTT in patients who retained functional hearing. Penetrating fibers were also found using DTT. This technique can be useful during VS resection.

Anatomical study of endoscope-assisted far lateral keyhole approach to the ventral craniocervical region with neuronavigational guidance.

BACKGROUND: Image-guided neurosurgery, endoscopic-assisted neurosurgery and the keyhole approach are three important parts of minimally invasive neurosurgery and have played a significant role in treating skull base lesions. This study aimed to investigate the potential usefulness of coupling of the endoscope with the far lateral keyhole approach and image guidance at the ventral craniocervical junction in a cadaver model. METHODS: We simulated far lateral keyhole approach bilaterally in five cadaveric head specimens (10 cranial hemispheres). Computed tomography-based image guidance was used for intraoperative navigation and for quantitative measurements. Skull base structures were observed using both an operating microscope and a rigid endoscope. The jugular tubercle and one-third of the occipital condyle were then drilled, and all specimens were observed under the microscope again. We measured and compared the exposure of the petroclivus area provided by the endoscope and by the operating microscope. Statistical analysis was performed by analysis of variance followed by the Student-Newman-Keuls test. RESULTS: With endoscope assistance and image guidance, it was possible to observe the deep ventral craniocervical junction structures through three nerve gaps (among facial-acoustical nerves and the lower cranial nerves) and structures normally obstructed by the jugular tubercle and occipital condyle in the far lateral keyhole approach. The surgical area exposed in the petroclival region was significantly improved using the 0° endoscope (1147.80 mm(2)) compared with the operating microscope ((756.28 ± 50.73) mm(2)). The far lateral retrocondylar keyhole approach, using both 0° and 30° endoscopes, provided an exposure area ((1147.80 ± 159.57) mm(2) and (1409.94 ± 155.18) mm(2), respectively) greater than that of the far lateral transcondylar transtubercular keyhole approach ((1066.26 ± 165.06) mm(2)) (P < 0.05). CONCLUSIONS: With the aid of the endoscope and image guidance, it is possible to approach the ventral craniocervical junction with the far lateral keyhole approach. The use of an angled-lens endoscope can significantly improve the exposure of the petroclival region without drilling the jugular tubercle and occipital condyle.

[Surgery for jugular foramen schwannomas via a pure endoscopic transoral approach].

OBJECTIVE: To report a new approach, endoscopic transoral approach for the resection of jugular foramen schwannoma. METHODS: Nine patients with jugular foramen schwannoma (three males and six females, ranging in age from 15 to 61 years old) were treated by direct surgery via a pure endoscopic transoral approach to the jugular foramen. Eight patients complained of hypoglossal nerve palsy with hemiatrophy of the tongue; six cases complained of vagus nerve palsy. Three cases complained of glossopharyngeal nerve palsy, one case complained of facial nerve palsy and hearing loss. RESULTS: The nerves in this area were preserved and radical intracapsular removal of the tumor was performed via endoscopic transoral approach in the nine cases. Tumor removal, as assessed by intraoperative endoscopic inspection, postoperative magnetic resonance imaging and clinical evaluation, revealed all tumors were completely removed. One patient suffered from temporary swallowing difficulties and temporary right vagus palsy 1 day after surgery. There were no others intraoperative and postoperative complications. All patients were followed up for 4 - 29 months, no recurrences were occurred in all these patients and the muscle bulk, motor and the pre-postoperative swallowing function, the vagus palsy, the facial nerve palsy and hearing loss had improved in these patients. CONCLUSION: The endoscopic transoral approach and intracapsular removal of the tumor provided for successful minimally invasive surgery in the jugular foramen schwannomas.

[Endoscopic endonasal surgery of trigeminal schwannoma extending into the infratemporal fossa].

OBJECTIVE: To investigate the feasibility of removing extracranial trigeminal schwannomas located in the infratemporal fossa by using a purely endoscopic endonasal approach. METHODS: From November 2004 to July 2009, 8 patients with extracranial trigeminal schwannomas located in the infratemporal fossa (4 male patients and 4 female patients, age ranged 31 - 62 years) were surgically treated by using a purely endoscopic endonasal approach. RESULTS: The maximum diameters of the tumors ranged from 3 to 7 cm. All tumors were completely removed. The operation time was 40 to 120 min, blood loss was 300 to 1500 ml. The clinical symptoms of some patients were relieved or improved. There were no intraoperative and postoperative complications, no deaths in this series. No relapse happened during the follow-up. CONCLUSIONS: The purely endoscopic endonasal approach may provide a minimally invasive and safe approach to remove extracranial trigeminal schwannomas extending into the infratemporal fossa. Radical resection is associated with an excellent long-term outcome in this series.

[Isolation and identification of brain tumor stem cells from human brain neuroepithelial tumors].

OBJECTIVE: To establish a simplified culture system for the isolation of brain tumor stem cells (BTSCs) from the tumors of human neuroepithelial tissue, to observe the growth and differentiation pattern of BTSCs, and to investigate their expression of the specific markers. METHODS: Twenty-six patients with brain neuroepithelial tumors underwent tumor resection. Two pieces of tumor tissues were taken from each tumor to be dissociated, triturated into single cells in sterile DMEM-F12 medium, and then filtered. The tumor cells were seeded at a concentration of 200,000 viable cells per mL into serum-free DMEM-F12 medium simply supplemented with B27, human basic fibroblast growth factor (20 microg/L), human epidermal growth factor (20 microg /L), insulin (4 U/L), L-glutamine, penicillin and streptomycin. After the primary brain tumor spheres (BTSs) were generated, they were triturated again and passed in fresh medium. Limiting dilution assay was performed to observe the monoclone formation. 5-bromodeoxyuridine (BrdU) incorporation test was performed to observe the proliferation of the BTS. The BTSCs were cultured in mitogen-free DMEM-F12 medium supplemented with 10% fetal bovine serum to observe their differentiation. Immunocytochemistry was used to examine the expression of CD133 and nestin, specific markers of BTSC, and the rate of CD133 positive cells. RESULTS: Only a minority of subsets of cells from the tumors of neuroepithelial tissue had the capacity to survive, proliferate, and generate free-floating neurosphere-like BTSs in the simplified serum-free medium. These cells attached to the poly-L-lysine coated coverslips in the serum-supplemented medium and differentiated. The BTSCs were CD133 and nestin positive. The rate of CD133 positive cells in the tumor specimens was (21 +/- 6.2)% - (38 +/- 7.0)%. CONCLUSION: A new simplified culture system for the isolation of BTSCs is established. The tumors of human neuroepithelial tissue contain CD133 and nestin positive tumor stem cells which can be isolated, proliferate and differentiate in vitro and give rise to brain tumor spheres. This tumorigenic subset may provide both a platform for brain tumor research and a target for clinical treatment.

[Correlation research between cancer stem cells and the pathological grades of neuroepithelial tumors].

OBJECTIVE: To explore the methods of isolation, culture and identification of brain tumor stem cells (BTSCs) in neuroepithelial tumor tissues in vitro, and to study the correlation between BTSCs and the patholorical grades of neuroepithelial tumors. METHODS: Tumor cells from patients undergoing neuroepithelial tumors excision were acutely dissociated, triturated into single cells, and then seeded into serum-free medium. After the primary brain tumor spheres (BTSs) were generated, they were triturated again and passaged in fresh medium. The expression of Nestin and CD133 of BTSs was detected by immunocytochemistry staining, and the expression of CD133 of tumor specimen sections was detected by immunohistochemistry staining . The expression of CD133 of 46 brain tumors and 5 normal brain tissues were analysed by SABC immunohistochemical staining, and the correlation between the expression and pathological grade of the tumors was analysed. RESULTS: BTSCs from neuroepithelial tumors could be isolated and cultured, and could be generated and passaged in vitro. The expression of Nestin and CD133 could be detected in BTSCs. CD133 could be detected in neuroepithelial tumor tissues, but not in normal brain tissues. There was significant difference between the expression of CD133 and the different grades of tumors (P < 0.01), and there was a positive correlation between the expression of CD133 and the histologic grading of tumors (P < 0.01). CONCLUSION: A small proportion of stem cells have the ability to self-renew in human neuroepithelial tumors, and there is a positive correlation between the expression of CD133 and histologic grading of tumors.

[Isolation and characterization of brain tumor stem cells in human medulloblastoma].

BACKGROUND & OBJECTIVE: Tumor stem cells have been isolated from several kinds of solid tumors, including primary brain tumors such as glioma and medulloblastoma. This investigation was to establish a simplified culture system to isolate and passage brain tumor stem cells (BTSCs) from human medulloblastoma, observe their proliferation and differentiation, and determine the expression of normal neural stem cell antigens, CD133 and Nestin, in BTSCs. METHODS: Eleven specimens of medulloblastoma were acutely dissociated and triturated into single cells without trypsin digestion. The tumor cells were seeded into serum-free DMEM/F12 medium (200,000 viable cells/ml) containing B27 (1:50), basic fibroblast growth factor (bFGF, 20 microg/L), epidermal growth factor (EGF, 20 microg /L), insulin (4 u/L), L-glutamine, and antibiotics. After generation, the primary brain tumor spheres (BTSs) were mechanically dissociated and passaged in the above serum-free medium. The monoclonal formation experiment was performed to determine the proportion of BTSCs in medulloblastoma and to observe the formation of BTSs. The differentiation of BTSCs was induced in mitogen-free DMEM/F12 medium supplemented with 10% fetal bovine serum. The expression of CD133 and Nestin in BTSs was observed with immunofluorescence staining; the distribution of CD133-positive cells in tumor sections was assessed by immunohistochemistry. RESULTS: In each of the 11 specimens, only a minority of medulloblastoma cells showed the capacity of self-renew and proliferation. These BTSCs generated free-floating neurosphere-like BTSs in the simplified serum-free medium. The proportion of BTSCs with monoclonal formation capacity in primary tumor cells was (31.18+/-6.18)%. The BTSCs attached to poly-L-lysine-coated coverslips and differentiated when the serum-supplemented medium was added. The expression of CD133 and Nestin was detected in BTSCs. CD133-positive cells scattered or formed nest-like aggregations in tumor masses, and accounted for (33.06+/-8.57)% of all tumor cells. CONCLUSIONS: BTSCs, with the capacity of self-renew and proliferation and express CD133 and Nestin, are exist in human medulloblastoma. They could be isolated and cultured in the simplified serum-free medium, and their differentiation could be induced in serum-supplemented medium.