A case of aggressive pituitary neuroendocrine tumour with extremely rapid progression: possible diagnostic value of TERT promoter methylation.

Most pituitary adenoma/neuroendocrine tumours (PitNET) are histologically benign and grow slowly; however, a subset of these tumours exhibit a more aggressive clinical course characterized by local invasiveness and early recurrence. These high-risk PitNETs often require multiple surgeries and radiation over several years and may eventually acquire carcinomatous characteristics, such as metastasis in some cases. Herein, we report a rare case of PitNET causing oculomotor paresis with extremely rapid recurrence only 3 months after initial surgery, followed by lethal liver metastasis. Preoperative magnetic resonance imaging and intraoperative findings were consistent with typical PitNETs, other than moderate invasion of the cavernous sinus. Pathological examination of the specimen obtained from the initial transsphenoidal surgery revealed increased mitosis and elevated rates of cells positive for Ki-67 and p53. Based on the immunohistochemical assessment for transcription factors and pituitary hormones, the diagnosis was determined to be a silent sparsely granulated corticotroph PitNET with focal malignant transformation. Aggressive features represented by Ki-67 and p53 positivity were more robust in recurrent and metastatic specimens, but hormone immunostaining was decreased. Epigenetic analysis revealed methylation of the telomerase reverse transcriptase (TERT) promoter in the tumour, resulting in TERT upregulation. Despite extensive research, markers for distinguishing extremely aggressive PitNETs have not been determined. Although further analysis is needed, our case demonstrates the possible usefulness of assessing TERT promoter methylation status in the stratification of recurrence risk in extremely high-risk variants of PitNET.

Extradural anterior temporal fossa approach to the paranasal sinuses, nasal cavities through the anterolateral and anteromedial triangles: Combined microscopic and endoscopic strategy.

OBJECTIVE: To demonstrate the utility and limitations of the extradural endoscopic-assisted anterior temporal fossa approach to the pterygopalatine fossa (PPF), infratemporal fossa (ITF), paranasal sinuses (PS), parapharyngeal region (PPR), nasal cavities (NC), epipharynx (EP), and clivus. METHODS: A frontotemporal orbitozygomatic craniotomy is performed. The dura is elevated from the cavernous sinus (CS). The anterior temporal fossa floor is drilled. Foramen rotundum and ovale are opened. The PPF is exposed and the lateral margin of inferior orbital fissure (IOF) is removed. The anterolateral triangle (ALT) is drilled and the vidian nerve (VN) is exposed. Drilling between the maxillary nerve (V2) and the VN provides access to the sphenoid sinus (SphS). The medial pterygoid plate is drilled exposing the EP. The maxillary sinus (MaxS) is opened anterior to the PPF. V2 is transposed laterally to enlarge the anteriomedial triangle (AMT). The orbital muscle of Muller is removed as well as the medial margin of the IOF, which opens the SphS. Anteriorly, the posterior ethmoid air cells are opened. Morphometric measurements evaluating the size of the ALT were done and the PS, NC, EP were explored with the endoscope. RESULTS: The ALT and AMT triangle provides a wide exposure of the PPF, ITF, PPR. In addition, those triangles represent a deep entry point to explore the PS, NC, and EP. CONCLUSION: The ALT and AMT are useful corridors to access to the SphS, MaxS, PS, NC, and EP via a transcranial approach. The use of the endoscope through this corridor widely extend the extradural anterior temporal fossa approach which may be considered as a valuable alternative to the extended endoscopic endonasal approach for selected skull base lesions extending both intracranial and into the PS, NC and EP.

Endoscopic endonasal approach to the mesial temporal lobe: anatomical study and clinical considerations for a selective amygdalohippocampectomy.

BACKGROUND: Selective amygdalohippocampectomy (AH) is a surgical option for patients with medically intractable seizures from mesial temporal lobe pathology. The transcranial route is considered the best method to achieve this goal. However, the standard approach through the neocortex is still invasive. The risks can be minimized if the mesial temporal lobe is resected while preserving the lateral temporal lobe and the Meyer's loop. This study explores the feasibility of selective AH by endoscopic endonasal approach (EEA) in cadaveric specimens. METHODS: The endoscopic anatomy of the mesial temporal lobe and the feasibility of a successful selective AH were studied in six hemispheres from three injected human cadavers. Quantitative analyses on the extent of resection and angles of exposure were performed based on CT and MRI studies of pre- and post-selective AH and measurements taken during dissections. RESULTS: The EEA V1-V2 corridor provided a direct and logical line of access to the mesial temporal lobe, following its natural trajectory with no brain retraction and minimal exposure of the pterygopalatine fossa. The components of the mesial temporal lobe were resected just as selectively and easily as the transcranial route, but without compromising the structures of the lateral temporal lobe or the Meyer's loop. CONCLUSIONS: The EEA V1-V2 corridor demonstrated its selective resectability and accessibility of the mesial temporal lobe in cadaveric specimens. The clinical value of this approach should be explored responsibly by a surgeon with both competent microsurgical skills and experiences in EEA.

How I do it: combined petrosectomy.

BACKGROUND: Petroclival lesions are among the most complex to address in skull base surgery, being closely related to critical neurovascular structures and brainstem. The combined petrosectomy allows a wide exposure of large petroclival lesions with short working distance and provides multiple angles of attack, while limiting brain retraction. METHOD: We describe in a step-wise fashion the surgical steps of the combined petrosectomy. CONCLUSION: Combined petrosectomy with posterior transposition of the transverse-sigmoid sinus provides a wide surgical corridor to the ventral brainstem, middle and upper clivus, and infra-retrochiasmatic region.

Spontaneous regression of meningiomas after interruption of nomegestrol acetate: a series of three patients.

BACKGROUND: The relationship between increased meningioma incidence and growth and long-term hormonal therapy with cyproterone acetate (CPA) in women has been recently established in literature. Following the raise in awareness from hormonal treatment, we describe a potential relationship between the progesterone agonist nomegestrol acetate (NOMAC) and meningioma growth. METHODS: After implementation of a screening protocol to detect potential interactions between hormonal exposure and occurrence of meningioma, we identified patients taking NOMAC and newly diagnosed with a meningioma. NOMAC was stopped and those patients were followed tightly both clinically and radiologically. Retrospective volumetric analysis of the tumors was performed on the imaging. RESULTS: Three patients were identified for the study. After cessation of the NOMAC, tumor shrinkage was documented for all meningiomas within the first month. Up to 70% of tumor volume reduction was observed during the first year of follow-up in one of them. None of the patients developed new symptoms. CONCLUSION: We report the first cases of meningiomas responsiveness to discontinuation of hormonal therapy with NOMAC. Similarly to cases associated with long-term CPA intake, tumor reduction, and improvement of clinical symptoms can be observed after cessation of NOMAC.

Risk Reduction of Cerebral Stroke After Stereotactic Radiosurgery for Small Unruptured Brain Arteriovenous Malformations.

BACKGROUND AND PURPOSE: A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA) indicated the superiority of medical management in reducing the risks for strokes and other neurological deficits over observation alone. The aim of our study was to verify the rationale for stereotactic radiosurgery (SRS) for small unruptured arteriovenous malformation. METHODS: A retrospective review was performed for 292 patients with unruptured arteriovenous malformations referred for SRS. The risks for cerebral hemorrhages were statistically compared before and after SRS. RESULTS: Of the 292 patients in whom arteriovenous malformation was found unruptured at initial diagnosis, 17 sustained hemorrhages in the period between the diagnosis and the initial therapeutic intervention (annual bleeding rate, 2.1%; 95% confidence interval [CI], 1.2%-3.4%). Of the remaining 275 patients, 240 were initially treated with SRS, and 16 sustained a hemorrhage after SRS (annual bleeding rate, 1.1%; 95% CI, 0.6%-1.8%), but only 2 sustained a hemorrhage after angiographic obliteration (annual bleeding rate, 0.3%; 95% CI, 0.04%-1.2%). Comparing the risk of hemorrhage between the periods before and after SRS, a 53% risk reduction was achieved after SRS (hazard ratio, 0.47; 95% CI, 0.24-0.94; P=0.03), and 85% reduction was achieved after angiographic obliteration (hazard ratio, 0.15; 95% CI, 0.02-0.53; P=0.002). CONCLUSIONS: SRS can significantly reduce the risk of stroke in the patients with small unruptured arteriovenous malformations. To definitively determine the clinical benefits of SRS, a longer follow-up will be necessary. However, based on our results, we can recommend SRS for patients who face a latent risk for stroke from this intractable vascular disease.

Application of single-stage stereotactic radiosurgery for cerebral arteriovenous malformations >10 cm3.

BACKGROUND AND PURPOSE: Stereotactic radiosurgery (SRS) is a safe and effective treatment for small arteriovenous malformations (AVMs), the use of this modality for the treatment of large AVMs is still controversial, although it has been used in difficult cases. The aim of this study was to evaluate the treatment outcomes of patients who underwent single-stage SRS for large AVMs and to discuss the role of SRS in the treatment of these challenging lesions. METHODS: Between 1998 and 2010, 65 patients with AVMs >10 cm(3) underwent single-stage SRS using the Leksell Gamma Knife. Patients who had prospective volume-staged SRS were excluded from this series. Outcomes including the rates of obliteration, hemorrhage after treatment, and adverse events were retrospectively evaluated. RESULTS: The mean nidus volume was 14.9 cm(3) (±3.8 cm(3)), and a mean margin dose of 20 Gy (±1.5 Gy) was applied. The mean observation period was 60 months (range, 7-178 months). The nidus obliteration rates after SRS were 44%, 76%, and 81% at 3, 5, and 6 years, respectively. The annual hemorrhage rate after SRS was 1.94% and permanent adverse events were observed in 2 patients (3%). CONCLUSIONS: For large AVMs <20 cm(3), single-stage radiosurgery by applying >16 Gy marginal dose presented favorable obliteration rates with relatively low rate of morbidity. Further accumulation of cases is awaited to fully evaluate the results of single-stage radiosurgery for large AVMs.

Corticospinal tract-sparing intensity-modulated radiotherapy treatment planning.

AIM: To establish intensity-modulated radiotherapy (IMRT) planning procedures that spare the corticospinal tract by integrating diffusion tensor tractography into the treatment planning software. BACKGROUND: Organs at risk are generally contoured according to the outline of the organ as demonstrated by CT or MRI. But a part of the organ with specific function is difficult to protect, because such functional part of the organ cannot be delineated on CT or conventional sequence of MRI. METHODS: Diagnostic and treatment planning images of glioblastoma patients who had been treated by conventional 3-dimensional conformal radiotherapy were used for re-planning of IMRT. Three-dimensional fiber maps of the corticospinal tracts were created from the diffusion tensors obtained from the patients before the surgery, and were blended with the anatomical MR images (i.e. gadolinium-enhanced T1-weighted images or T2-weighted images). DICOM-formatted blended images were transferred and fused to the planning CT images. Then, IMRT plans were attempted. RESULTS: The corticospinal tracts could be contoured as organs at risk (OARs), because the blended images contained both anatomical information and fiber-tract maps. Other OARs were contoured in a way similar to that of ordinary IMRT planning. Gross tumor volumes, clinical target volumes, planning target volumes, and other OARs were contoured on the treatment planning software, and IMRT plans were made. CONCLUSIONS: IMRT plans with diminished doses to the corticospinal tract were attained. This technique enabled us to spare specific neuron fibers as OARs which were formerly "invisible" and to reduce the probability of late morbidities.

Surgical Outcomes following Reoperation for Recurrent Intracranial Meningiomas.

Background: We sometimes encounter refractory meningioma cases that are difficult to control, even after achieving a high resection rate or following radiation therapy (RT). In such cases, additional surgical resection might be attempted, but reports regarding outcomes of re-do surgery for recurrent meningiomas are scarce. Methods: This study was a retrospective review of patients who underwent re-do surgery for recurrent meningiomas. The risks of re-doing surgery were statistically analyzed. A comparative analysis between the patients who underwent primary surgery for intracranial meningiomas was also performed. Twenty-six patients underwent re-do surgeries for recurrent meningiomas. Results: At first re-do surgery, gross total resection was achieved in 20 patients (77%). The disease-free survival rate after the first re-do surgery was calculated as 73/58/44% at 1, 2, and 5 years, respectively. A significant factor affecting longer disease-free survival was WHO Grade 1 diagnosis at first re-do surgery (p = 0.02). Surgery-related risks were observed in 10 patients presenting a significant risk factor for skull base location (p = 0.04). When comparing with the risk at primary surgery, the risks of surgical site infection (p = 0.04) and significant vessel injury (p < 0.01) were significantly higher for the re-do surgery. Conclusions: Re-do surgery could increase surgery-related risks compared to the primary surgery; however, it could remain a crucial option, while the indication should be carefully examined in each case.

Unmanageable Cerebrospinal Fluid Leakage With Eosinophilic Meningitis in a Gliadel Wafer Implant Patient.

Gliadel wafer implants (Eisai Inc., Woodcliff Lake, NJ, USA) have shown their efficacy in prolonging survival in patients with malignant gliomas. The safety of Gliadel wafers has also been reported; however, there is a certain risk of adverse events. We present a rare case of refractory cerebrospinal fluid (CSF) leakage with eosinophilic meningitis in a patient with glioblastoma who underwent tumor resection with Gliadel wafer implants. A 60-year-old man presented with a glioblastoma in the right temporal lobe. The patient underwent tumor resection with Gliadel wafer implants. During the postoperative course, the patient presented with intractable CSF leakage and the development of a pseudomeningocele. A delayed rise in blood and CSF eosinophil count (a few weeks after the primary operation) and positive drug-induced lymphocyte stimulation test (DLST) results against the Gliadel wafer led to the diagnosis of an allergic reaction to these implants. Removal of the Gliadel wafers resolved the eosinophilic reaction; however, the patient subsequently required a shunt procedure for persistent hydrocephalus. This case highlights the importance of investigating rare causes of refractory CSF leakage and hydrocephalus due to allergic reactions to Gliadel wafers. Delayed elevations of eosinophils in blood and CSF tests may lead to a diagnosis of eosinophilic meningitis. DLST against Gliadel wafers is also useful for diagnosis when it is available. To control the hydrocephalus, not only the shunt procedure but also wafer removal must be considered; however, patients with limited life expectancy are generally hesitant to undergo such additional procedures.

Pearls & Oy-sters: Cognitive and Affective Dysfunction Caused by a Small Cerebellar Hemangioblastoma.

The primary function of the cerebellum is the coordination and regulation of movement; therefore, cerebellar tumors usually present with ataxia, dysarthria, and vertigo. Large tumors also cause elevated intracranial pressure that may lead to a disturbance of consciousness. Furthermore, it has become increasingly evident that the cerebellum plays a substantial role in cognitive and affective processing. A 44-year-old female patient presented with a 1-month history of depression and flat affect. She had no cerebellar symptoms including no coordination dysfunction or dysarthria. Cognitive function tests revealed impairments in attention, execution, and processing speed. Hamilton Depression Scale and Hospital Anxiety Depression Scale indicated moderate-to-severe depression. Magnetic resonance (MR) imaging revealed a 7-mm enhancing lesion in the culmen of the cerebellar vermis with surrounding edema. Technetium-99m ethyl cysteinate dimer single-photon emission tomography (SPECT) showed hypoperfusion in the left frontal lobe. Although she was initially treated with corticosteroids for presumed sero-negative autoimmune encephalitis, her symptoms persisted. She then underwent cerebellar lesion resection. The histologic diagnosis was hemangioblastoma. The patient's symptoms dramatically improved within 1 week of resection, including improved batteries for cognitive function and depression. Complete regression of cerebellar edema and left frontal lobe hypoperfusion was observed on MR and SPECT images, respectively. This case reiterates the crucial influence of the cerebellum on cognitive and affective function. Moreover, cognitive dysfunction may be masked in cases with focal cerebellar symptoms or elevated intracranial pressure and, consequently, not adequately evaluated.

Endoscopic Extended Transsphenoidal Surgery Aiming for Radical Resection of Skull Base Tumors Involving Cavernous Sinus: Assessment of Resectability and Risks of Complications.

BACKGROUND AND OBJECTIVES: Surgical resection of tumors invading the cavernous sinus (CS) still shows therapeutic challenges. For "nonadenomatous" skull base tumors invading in CS, there were only a few reports showing the outcomes of radical resection. Therefore, the outcomes of endoscopic transsphenoidal surgery (ETS) aiming for radical resection thus remain largely unknown regarding resectability and functional results of the cranial nerves. METHODS: We performed ETS aiming for radical resection in 35 skull base tumors involving CS (17 chondrosarcomas, 12 chordomas, 3 meningiomas, and 3 trigeminal schwannomas; median follow-up 36.5 months ranging from 12 to 91 months). Gross total resection (GTR) is attempted in all the cases for real-time findings from electrophysiological monitoring of the cranial nerves. When the tumor was strongly adherent to the cranial nerves or internal carotid artery, maximum volume reduction of the tumor was attempted. RESULTS: GTR was achieved in 28 patients (80.0%), subtotal resection in 3 (8.6%), and partial resection in 4 (11.4%). One patient experienced internal carotid artery injury during surgery. After ETS, 15 patients showed symptom improvement (51.7% in all 29 patients with preoperative cranial nerve symptoms, CNS). Four (11.4%) transiently developed abducens nerve palsy, and one required repair surgery for cerebrospinal leakage. In univariate analyses, extension to the lateral compartment of CS ( P = .04) was significantly associated with reduced achievement of GTR. Previous transcranial surgery was associated with reduced possibility of improvement and worsening in CNS. Eleven patients underwent stereotactic radiosurgery, at a median of 12 months after ETS. 32 patients (91.4%) did not show recurrence at the final follow-up. CONCLUSION: ETS can achieve sufficient surgical resection in most of the patients, with acceptable neurological complications. For patients with CNS, ETS may offer the opportunity for improving CNS. We should also always prioritize avoidance of critical situations by preventing internal carotid artery injury.

Age-Dependent Hemorrhage Risk and Obliteration Benefit After Radiosurgery for Brain Arteriovenous Malformation.

PURPOSE: Because patients with untreated brain arteriovenous malformations (BAVMs) are at variable risks of cerebral hemorrhage and associated mortality and morbidity, it is essential to identify patient populations who benefit most from prophylactic interventions. This study aimed to examine age-dependent differences in the therapeutic effect of stereotactic radiosurgery (SRS) on BAVMs. METHODS AND MATERIALS: This retrospective observational study enrolled patients with BAVMs who underwent SRS at our institution between 1990 and 2017. The primary outcome was post-SRS hemorrhage, and the secondary outcomes included nidus obliteration, post-SRS early signal changes, and mortality. To investigate age-related differences in outcomes after SRS, we performed age-stratified analyses using the Kaplan-Meier analysis and weighted logistic regression with the inverse probability of censoring weighting (IPCW). To address significant differences in patient baseline characteristics, we also performed inverse probability of treatment weighting (IPTW) adjusted for possible confounders to investigate age-related differences in outcomes after SRS. RESULTS: A total of 735 patients with 738 BAVMs were stratified by age. Age-stratified analysis using a weighted logistic regression model with IPCW showed a direct correlation between patient age and post-SRS hemorrhage (odds ratio [OR], 95% confidence interval [CI], and P value: 2.20, 1.34-3.63, and .002 at 18 months; 1.86, 1.17-2.93, and .008 at 36 months; and 1.61, 1.05-2.48, and .030 at 54 months, respectively). The age-stratified analysis also showed an inverse relationship between age and obliteration over the first 42 months after SRS (OR, 95% CI, and P value: 0.05, 0.02-0.12, and <.001 at 6 months; 0.55, 0.44-0.70, and <.001 at 24 months; and 0.76, 0.63-0.91, and .002 at 42 months, respectively). These results were also confirmed with the IPTW analyses. CONCLUSIONS: Our analysis demonstrated that patients' age at SRS is significantly associated with hemorrhage and the nidus obliteration rate after treatment. In particular, younger patients are more likely to exhibit reduced cerebral hemorrhages and achieve earlier nidus obliteration compared with older patients.

Ventriculoperitoneal Shunt Malfunction in a Pediatric Patient Due to Compression by Skull Growth: A Case Report.

There are various causes of ventriculoperitoneal shunt (VPS) failures. Patients who receive shunt placement during childhood need follow-up for decades as they grow, especially in the early periods of life. Herein, we report a rare case of mechanical shunt obstruction in a pediatric patient in whom a cramped burr hole and skull growth compressed the tube and obstructed cerebrospinal fluid flow. A 6-year-old girl presented to our hospital with nausea and headache. She was born preterm and developed intraventricular hemorrhage followed by VPS placement for hydrocephalus; thereafter, she had no need for shunt revision until this admission. After careful evaluation of the patency of the shunt system, the presence of tube stenosis was suspected at the site of the shunt tube penetrating the burr hole of the skull. During the operation to revise the shunt tube, a compressed tube was observed at the exit from the skull. After enlarging the narrowed burr hole and reconstructing the proximal catheter, her symptoms immediately improved. Previously, only one case of shunt malfunction due to tube compression from bone growth has been reported in a pediatric patient with osteopetrosis. To the best of our knowledge, such a condition has never been described in pediatric patients with no metabolic bone disease. Although it is rare, obstruction at the exit from the skull due to bone growth should be included in differential diagnoses for young patients during a long follow-up after VPS.

Quantitative Evaluation of Proliferative Potential Using Flow Cytometry Reveals Intratumoral Heterogeneity and Its Relevance to Tumor Characteristics in Vestibular Schwannomas.

This study sought to explore the existence and clinical significance of intratumoral heterogeneity of proliferative potential in vestibular schwannoma (VS). Rapid intraoperative flow cytometry was utilized with raw samples to measure the proliferative ability of VS. The proliferation index (PI) was defined as the ratio of the number of cells with greater than normal DNA content to the total number of cells. A total of 66 specimens (26 from the intrameatal portion and 40 from the cisternal portion) were obtained from 34 patients with VS. There was a moderate correlation between the PI and MIB-1 labelling index values (R = 0.57, p < 0.0001). In contrast, the patterns of heterogeneity, represented by the proportion of intrameatal PI to cisternal PI, were associated with tumor size (p = 0.03). In addition, preoperative hearing tended to be poor in cases where the intrameatal PI was higher than the cisternal PI (p = 0.06). Our data demonstrated the presence of intratumoral heterogeneity of proliferative potential in VS and its relationship with tumor characteristics. The results of this study may advocate the resection of the intrameatal portion of large VSs treated with planned subtotal resection, especially in cases of poor preoperative hearing function.

Trigeminal neuralgia due to intracranial venous reflux following central venous disease in a patient on hemodialysis: A case report.

Background: A wide variety of conditions can cause trigeminal neuralgia (TN). Case Description: We describe a rare case of a 77-year-old female patient on hemodialysis presenting with severe TN on the right side of the face for several weeks. She underwent multiple revisions using catheter for brachiocephalic venous stenosis over 6 years after a therapeutic arteriovenous fistula (AVF) was created in the left forearm. Her facial pain was consistent with Type 1 TN and remained intractable even after carbamazepine treatment. The initial magnetic resonance imaging did not demonstrate arterial compression on the right trigeminal nerve; instead, the vein adjacent to the right trigeminal nerve showed a hyperintense signal. In addition, the contralateral cortical veins and transverse sigmoid sinus were dilated. Angiography from the left brachial artery revealed intracranial venous reflux (IVR) through the left jugular vein due to an occluded brachiocephalic vein. Her pain was relieved immediately after her left upper arm was compressed with a sphygmomanometer to decrease the shunt. Surgical elimination of the AVF on the left forearm resulted in complete resolution of TN. Postoperative radiological examination revealed the resolution of IVR, and her TN has not recurred by her 6-month follow-up. Conclusion: The radiological diagnosis of IVR might be complicated because the true causative lesion for focal neurological symptoms might be remotely located. IVR following central venous disease should be a differential when patients on hemodialysis present neurological symptoms.

High Dose Radiosurgery Targeting the Primary Tumor Sites Contributes to Survival in Patients With Skull Base Chordoma.

PURPOSE: Skull base chordoma (SBC) is a rare, aggressive bone tumor and a challenging therapeutic target. The efficacy of stereotactic radiosurgery (SRS) for SBC remains unclear. We aimed to elucidate therapeutic factors for favorable outcomes and establish a novel therapeutic approach for SBC. METHODS AND MATERIALS: This single-center retrospective study examined 47 SBCs treated with SRS. Treatment factors affecting local control rates (LCRs), remote control rates (RCRs), and overall survival (OS) were evaluated. Initially, we applied "localized-field SRS," wherein the irradiated volume accurately included recurrent/residual tumors on the radiographic images. Since 2015, we systematically applied "extended-field SRS," wherein the irradiated volume included the tumor location on the radiographic images and the preoperative tumor location with 2-mm margins. RESULTS: Tumor progression was observed in 23 SBCs (49%) after SRS. Higher marginal doses ≥20 Gy resulted in a higher LCR than lower-dose treatments (92% at 2 years and 73% at 5 years vs 43% at 2 years and 21% at 3 years, P = .001). Twenty-four patients underwent extended-field SRS, and 23 underwent localized-field SRS. While the LCRs were not significantly different, extended-field SRS improved RCRs (extended-field SRS: 100% vs localized-field SRS: 46% at 5 years; P = .001) without radiation-induced adverse events. Multivariate analysis demonstrated that extended-field SRS was associated with better RCRs (P = .001) and OS (P = .001). CONCLUSIONS: Extended-field SRS achieved LCRs comparable to previous studies and excellent OS without increasing the risk of radiation-induced adverse events.

Trigeminal neuralgia caused by an arachnoid cyst in Meckel's cave: A case report and literature review.

BACKGROUND: We present a rare case of trigeminal neuralgia (TN) caused by an arachnoid cyst (AC) in Meckel's cave (MC). CASE DESCRIPTION: A 35-year-old man presented with facial pain in the left maxillary and mandibular regions. Since the initial magnetic resonance (MR) imaging showed no apparent offending vessels or tumors, the patient was diagnosed with idiopathic TN, for which carbamazepine was initially effective. When his pain worsened, he was referred to our hospital. A slightly asymmetric shape of MC and distorted course of the trigeminal nerve was confirmed on the initial and repeat MR images. His pain was characterized as electric-shock-like pain, which was triggered by touching the face. Under the tentative diagnosis of an AC confined to MC compressing the trigeminal nerve, the exploration of MC through suboccipital craniotomy was performed. Intraoperatively, the AC was identified in the rostral portion of MC. The indentation of the trigeminal nerve was also observed at the orifice of MC, indicating severe compression by the AC. The wall of the AC was fenestrated. The patient's pain was relieved immediately after surgery. Postoperative MR images showed that the course of the trigeminal nerve was straightened. Although our literature review found five similar cases, the size of the AC was the smallest in our case. CONCLUSION: Although it is rare, the AC confined to MC can cause TN. The findings of this study emphasize the importance of evaluating subtle radiological findings of compression on the trigeminal nerve in cases of TN seemingly without neurovascular compression.

Re-Evaluation of the Size Limitation in Single-Session Stereotactic Radiosurgery for Brain Arteriovenous Malformations: Detailed Analyses on the Outcomes with Focusing on Radiosurgical Doses.

BACKGROUND: Single-session stereotactic radiosurgery (SRS) for large arteriovenous malformations (AVMs) ≥10 mL remains controversial, which is considered as the current size limitation. OBJECTIVE: To reconsider the size limitation of SRS for AVMs by profoundly analyzing dose-volume relationship. METHODS: Data on 610 consecutive patients with AVM treated with SRS using regular (18-22 Gy) or low (<18 Gy) prescription doses were retrospectively analyzed. AVMs were classified into 4 groups: small (<5 mL), medium (≥5 and <10 mL), medium-large (≥10 and <15 mL), and large (≥15 mL). The maximum volumes were 22.5 mL (regular-dose group) and 23.5 mL (low-dose group). RESULTS: When treated with regular doses, the cumulative 6-yr obliteration rates for each of the 4 AVM groups were 86%, 80%, 87%, and 79%, respectively; the cumulative 10-yr significant neurological event (SNE) rates were 2.6%, 3.9%, 6.8%, and 5.3%, respectively. Regarding large AVMs, regular-dose SRS resulted in marginally better obliteration rate (6-yr cumulative rate, 79% vs 48%, P = .111) and significantly lower SNE (5-yr cumulative rate, 5% vs 31%, P = .038) and post-SRS hemorrhage rate (8-yr cumulative rate, 0% vs 54%, P = .002) compared to low-dose SRS. Multivariate analyses revealed that regular-dose SRS significantly contributed to increase in the obliteration rate and decrease in SNEs and hemorrhage. CONCLUSION: The outcomes for large AVMs were generally favorable when treated with ablative doses. Single-session SRS could be acceptable for AVMs up to ≈20 mL if treated with ablative doses.

The orbitopterygoid corridor as a deep keyhole for endoscopic access to the paranasal sinuses and clivus.

OBJECTIVE: The anteromedial triangle (AMT) is the triangle formed by the ophthalmic (V1) and maxillary (V2) nerves. Opening of this bony space offers a limited access to the sphenoid sinus (SphS). This study aims to demonstrate the utility of the orbitopterygopalatine corridor (OPC), obtained by enlarging the AMT and transposing the contents of the pterygopalatine fossa (PPF) and V2, as an entrance to the SphS, maxillary sinus (MaxS), and nasal cavity. METHODS: Five formalin-injected cadaveric specimens were used for this study (10 approaches). A classic pterional approach was performed. An OPC was created through the inferior orbital fissure, between the orbit and the PPF, by transposing the PPF inferiorly. The extent of the OPC was measured using neuronavigation and manual measurements. Two illustrative cases using the OPC to access skull base tumors are presented in the body of the article. RESULTS: Via the OPC, the SphS, MaxS, ethmoid sinus (EthS), and nasal cavity could be accessed. The use of endoscopic assistance through the OPC achieved better visualization of the EthS, SphS, MaxS, clivus, and nasal cavity. A significant gain in the area of exposure could be achieved using the OPC compared to the AMT (22.4 mm2 vs 504.1 mm2). CONCLUSIONS: Opening of the AMT and transposition of V2 and the contents of the PPF creates the OPC, a potentially useful deep keyhole to access the paranasal sinuses and clival region through a middle fossa approach. It is a valuable alternative approach to reach deep-seated skull base lesions infiltrating the cavernous sinus and middle cranial fossa and extending into the paranasal sinus.