Evaluation of cranial nerve involvement in chordomas and chondrosarcomas: a retrospective imaging study.

PURPOSE: Cranial nerve involvement (CNI) influences the treatment strategies and prognosis of head and neck tumors. However, its incidence in skull base chordomas and chondrosarcomas remains to be investigated. This study evaluated the imaging features of chordoma and chondrosarcoma, with a focus on the differences in CNI. METHODS: Forty-two patients (26 and 16 patients with chordomas and chondrosarcomas, respectively) treated at our institution between January 2007 and January 2023 were included in this retrospective study. Imaging features, such as the maximum diameter, tumor location (midline or off-midline), calcification, signal intensity on T2-weighted image, mean apparent diffusion coefficient (ADC) values, contrast enhancement, and CNI, were evaluated and compared using Fisher's exact test or the Mann-Whitney U-test. The odds ratio (OR) was calculated to evaluate the association between the histological type and imaging features. RESULTS: The incidence of CNI in chondrosarcomas was significantly higher than that in chordomas (63% vs. 8%, P < 0.001). An off-midline location was more common in chondrosarcomas than in chordomas (86% vs. 13%; P < 0.001). The mean ADC values of chondrosarcomas were significantly higher than those of chordomas (P < 0.001). Significant associations were identified between chondrosarcomas and CNI (OR = 20.00; P < 0.001), location (OR = 53.70; P < 0.001), and mean ADC values (OR = 1.01; P = 0.002). CONCLUSION: The incidence of CNI and off-midline location in chondrosarcomas was significantly higher than that in chordomas. CNI, tumor location, and the mean ADC can help distinguish between these entities.

Successful surgical treatment of oculomotor palsy due to schwannoma of the cavernous sinus in a 7-year-old girl: a case report.

Oculomotor nerve schwannoma in children not associated with neurofibromatosis is a rare disease, with 26 pediatric cases reported so far. There is no established treatment plan. A 7-year-old girl presented with oculomotor nerve palsy. Surgical reduction of the tumor combined with postoperative gamma knife surgery preserved the oculomotor nerve, improved oculomotor nerve function, and achieved tumor control during the observation period of 20 months. The combination of partial surgical resection and gamma knife surgery as a treatment strategy for oculomotor nerve schwannoma resulted in a good outcome.

Changes in interhemispheric coherence after total corpus callosotomy: a scalp EEG study in children with non-lesional generalized epilepsy.

PURPOSE: Coherence analysis in electroencephalography (EEG) allows measurement of the degree of consistency of amplitude between pairs of electrodes. Theoretically, disconnective epilepsy surgery should decrease coherence between corresponding areas. The study aimed to evaluate postoperative changes in interhemispheric coherence values after corpus callosotomy (CC). METHODS: Non-lesional, drug-resistant, generalized epilepsy patients who underwent total CC were retrospectively collected. To evaluate coherence, we divided the scalp interictal EEG into "baseline" and "discharge" states after excluding periods with artifacts. Interhemispheric coherence values were obtained between eight pairs of symmetrically opposite scalp electrodes in six different frequency bands. We analyzed both pre- and postoperative EEG sessions and calculated the percentage of difference (POD) in coherence values. RESULTS: We collected 13 patients and analyzed 2496 interhemispheric coherence values. Preoperative coherence values differed significantly between baseline and discharge states (p = 0.0003), but postoperative values did not (p = 0.11). For baseline state, coherence values were decreased after CC and median POD was - 22.3% (p < 0.0001). Delta frequency showed the most decreased POD (-44.3%, p = 0.0009). Median POD was lowest in the Fp1-Fp2 pair of electrodes. For discharge state, coherence values were decreased after CC and median POD was - 24.7% (p < 0.0001). Delta frequency again showed the most decreased POD (-55.9%, p = 0.0016). Median POD was lowest in the F7-F8 pair. CONCLUSION: After total CC, interhemispheric coherence decreased significantly in both baseline and discharge states. The most decreased frequency band was the delta band, which may be used as a representative frequency band in future studies.

[Endoscopic Surgery for Skull Base Tumors].

With the development of endoscopic and peripheral instruments, endonasal or transcranial endoscopic surgery for skull-base tumors has become more common. Preoperative simulation makes it relatively easy to understand the anatomical relationship between skull base tumors and the surrounding vital structures, which vary with each case. This may lead to the avoidance of complications and an improvement in the removal rate. Especially in cases of skull base tumors where multiple surgical approaches are possible, the three-dimensional model can be used to confirm the surgical field for each approach and consider the most appropriate. With the development of endovascular treatment and radiotherapy, experience in craniotomy has decreased. Young neurosurgeons need to develop skills to learn as efficiently as possible from their limited experience. Therefore, it is extremely useful to provide an environment that allows for easier preoperative simulations.

Endoscopic endonasal approach to remove pediatric intraventricular tumors of the third ventricle.

PURPOSE: Pediatric intraventricular tumors of the third ventricle are among the most difficult-to-treat brain tumors. Recently, endonasal endoscopic surgery for suprasellar, third ventricle, and median clivus lesions has become the common procedure, and its indications are expanding to pediatric cases. We describe our strategy for endonasal endoscopic surgery for pediatric third ventricle tumors. METHOD: We report on surgical anatomies and our surgical procedures in detail, including case presentations. RESULT: Endoscopic endonasal surgery has the advantage of providing a wider view of the tumor site, hypothalamus, optic chiasm, and other critical structures. Good indications for the endoscopic endonasal approach for intra-third ventricular tumors are those arising from the floor of the third ventricle. In particular, craniopharyngioma, a typical pediatric suprasellar tumor, sometimes extends into the third ventricle, causing great operative difficulty. However, aggressive removal for long-term control while preserving memory and visual function is important. We perform surgery with a strategy of radically removing tumors without causing damage to visual or brain function, and we adopt the "4-hands technique by two neurosurgeons" in full endoscopic surgery to remove tumors safely and aggressively. CONCLUSION: We describe our strategy for endonasal endoscopic surgery for pediatric third ventricle tumors, especially those extending from the suprasellar region into the third ventricle, and present a representative case.

Surgical Strategy in Modification of the Transpetrosal Approach to Avoid Postoperative Venous Complications: A Report of 74 Consecutive Cases.

BACKGROUND: The transpetrosal approach is a complex skull base procedure with a high risk of complications, particularly caused by injury of the venous system. It is in part related to variability of blood outflow pathways and their distinctive patterns in each individual patient. OBJECTIVE: To evaluate outcomes and complications after skull base surgery with use of the petrosal approach modifications, which selection was based on the detailed preoperative assessment of venous drainage patterns. METHODS: Overall, 74 patients, who underwent surgery via the transpetrosal approach at our institution between 2000 and 2017, were included in this study. In all cases, the venous drainage pattern was assessed preoperatively and categorized according to the predominant blood outflow pathway into four types as previously suggested by Hacker: (1) sphenoparietal sinus (SpPrt), (2) sphenobasal vein (SpB), (3) sphenopetrosal sinus (SpPS), and (4) cortical. The blood outflow through the bridging petrosal vein and the vein of Labbé was also taken into consideration. In patients with SpPrt- and a cortical-type venous drainage, the transpetrosal approach was used in a standard way. In patients with SpB-type venous drainage, limited extradural anterior petrosectomy was combined with intradural anterior petrosectomy after dural opening, superior petrosal sinus transection, tentorial cutting, Meckel's cave opening, and trigeminal nerve mobilization. In patients with SpPS-type venous drainage, after standard petrosectomy, dural opening, and tentorial cutting, SpPS ligation was done followed by 2-week interval before staged definitive tumor resection. RESULTS: Gross total, near-total, and subtotal resection of the lesion (meningioma, 48 cases; retrochiasmatic craniopharyngioma, 11 cases; brain stem cavernoma, 7 cases; other tumors, 8 cases) was achieved in 30 (40.5%), 24 (32.4%), and 20 (27.0%) patients, respectively. Postoperative complications that were possibly related to venous compromise were noted in 18 patients (24.3%), but neither one was major. Of these 18 patients, 9 were symptomatic, but all symptoms-aphasia (4 cases), seizures (2 cases), and confusion (3 cases)-fully resolved after conservative treatment. Overall, 13 patients, including 4 symptomatic, had signal changes on T2-weighted brain MRI, which were permanent only in 3 cases (all asymptomatic). CONCLUSION: Our suggested surgical strategy can be applied to any type of the venous drainage pattern. Preoperative evaluation and intraoperative preservation of the blood outflow pathways are crucial means for safe and effective application of the transpetrosal approach.

[Surgical Approaches to Craniopharyngiomas].

Surgical treatment of craniopharyngioma still presents several challenges. The tumor recurs at a high rate when its removal is insufficient. However, total resection of the tumor has a high risk of complications owing to its proximity to the hypothalamus and the pituitary stalk. In addition, tumor control by radiation treatment is insufficient for long follow-up periods of over 10 years. Therefore, various treatments have been selected, ranging from partial tumor removal followed by radiation to total tumor removal, even if it involves sacrificing pituitary functions. In this article, we explain the surgical treatment with a focus on endoscopic endonasal surgery for craniopharyngiomas.

[Surgical Treatment of Mesial Temporal Lobe Epilepsy Focusing on Anatomical Understanding].

Surgical treatment is an effective option for medically intractable epilepsy. Amygdalohippocampectomy for mesial temporal lobe epilepsy is a surgically remediable epileptic syndrome. It is a well-established surgery and various approaches to the mesial temporal lobe have been reported. To reduce the complication rate, surgeons should have sufficient knowledge of anatomy in the mesial temporal region. Here, we summarize the surgical treatments for mesial temporal lobe epilepsy, focusing on anatomical understanding. We described in detail the surgical anatomy of amygdalohippocampectomy and various approaches to the mesial temporal region. In addition, we describe hippocampal transection aimed at preserving memory function, which is an alternative surgery in patients without hippocampal sclerosis. An anatomical understanding of the mesial temporal region helps surgeons not only in the field of epilepsy surgery, but also in other fields of neurosurgery, such as brain tumor and vascular surgery.

TSC2 somatic mosaic mutation, including extra-tumor tissue, may be the developmental cause of solitary subependymal giant cell astrocytoma.

PURPOSE: Subependymal giant cell astrocytomas (SEGAs) are tumors that usually arise in the wall of one or the other lateral ventricle near a foramen of Monro, most often on a background of tuberous sclerosis complex (TSC). TSC has a variety of clinical manifestations caused by germline mutations of the TSC complex subunit 1 or 2 (TSC1, TSC2) genes. SEGAs without clinical manifestations of TSC are termed solitary SEGAs, which are hypothesized to be caused by tumor-only TSC1/2 mutations, or "forme fruste" of TSC with somatic mosaic mutations. However, it is difficult to distinguish between the two. Here, we report three patients with genetically investigated solitary SEGAs and review this rare manifestation. METHODS: SEGA was completely removed in two patients and partially removed in one. Genetic analyses were performed on the tumor tissue and on peripheral blood via DNA microarray, reverse-transcriptase polymerase chain reaction, and next-generation sequencing with ultra-deep sequencing of mutation points. RESULTS: All three patients had tumors with TSC2 somatic mutations and loss of heterozygosity (LOH). In one patient, the same TSC2 mutation was also detected in 1% of leukocytes in his blood. The tumors did not recur, and clinical manifestations of TSC did not develop during the 4-year follow-up. CONCLUSIONS: The genetic cause of solitary SEGAs may be a TSC2 mutation with LOH. In patients with solitary SEGA, mosaic mutations may present in other organs, and TSC may clinically manifest later in life; therefore, patients should be followed up for prolonged periods.

[The Combined Petrosal Approach].

The combined petrosal approach can provide a wide and shallow surgical field around the ventral surface of the brain stem and the petroclival area. The minimal anterior and posterior combined petrosal approach(MAPCPA)is one modification of the combined petrosal approach. It offers the same wide surgical space in the subdural area and limits bone works and surgical time. Each surgical step of the MAPCPA is demonstrated in detail using several figures and a surgical video.

[How to Use a High-Speed Drill and an Ultrasonic Aspirator During Skull Base Surgery].

During surgery for skull base lesions, maximum efforts should be made to improve the removal rate of the lesion while avoiding complications, and it is necessary to expand the surgical field by selecting appropriate surgical instruments and equipment. In both microsurgery and endoscopic surgery, high-speed drills and ultrasonic aspirators contribute significantly to the safe and reliable removal of skull base lesions, and the surgeons need to be familiar with these characteristics. The specific vital points are as follows: (1) Preparation of the appropriate environment for using a high-speed drill or an ultrasonic aspirator with the understanding of the microsurgical anatomy, (2) Bone excision using a high-speed drill with the selection of an appropriate drill attachment or drill bar tip according to the site of use, (3) Internal decompression of lesions using an ultrasonic aspirator with appropriate settings, (4) Additional expansion of the surgical field by using an ultrasonic aspirator in the osteotomy mode, and so on. This section describes details of how to use a high-speed drill and an ultrasonic aspirator during skull base surgery.

[Endoscopic Endonasal Surgery for Pediatric Suprasellar Tumors].

Pediatric suprasellar tumors are difficult to treat. Their sellar-suprasellar location frequently results in compression of the adjacent critical neurovascular structures, making them a challenging surgical entity. Our surgical strategy emphasizes on radical resection of the tumor without compromising visual or cognitive functions. In recent years, the endoscopic endonasal approach has been increasingly used for pediatric suprasellar tumors. We have adopted a "4-hand technique by two neurosurgeons" during endoscopic endonasal surgery to resect aggressive tumors safely. Posterior clinoidectomy and upper clivectomy are useful additional procedures to resect intra-3rd-ventricle and retrochiasmatic suprasellar tumors. Here, we present our surgical management strategy and tips for endonasal resection of pediatric suprasellar tumors.

Deep Learning-based Angiogram Generation Model for Cerebral Angiography without Misregistration Artifacts.

Background Digital subtraction angiography (DSA) generates an image by subtracting a mask image from a dynamic angiogram. However, patient movement-caused misregistration artifacts can result in unclear DSA images that interrupt procedures. Purpose To train and to validate a deep learning (DL)-based model to produce DSA-like cerebral angiograms directly from dynamic angiograms and then quantitatively and visually evaluate these angiograms for clinical usefulness. Materials and Methods A retrospective model development and validation study was conducted on dynamic and DSA image pairs consecutively collected from January 2019 through April 2019. Angiograms showing misregistration were first separated per patient by two radiologists and sorted into the misregistration test data set. Nonmisregistration angiograms were divided into development and external test data sets at a ratio of 8:1 per patient. The development data set was divided into training and validation data sets at ratio of 3:1 per patient. The DL model was created by using the training data set, tuned with the validation data set, and then evaluated quantitatively with the external test data set and visually with the misregistration test data set. Quantitative evaluations used the peak signal-to-noise ratio (PSNR) and the structural similarity (SSIM) with mixed liner models. Visual evaluation was conducted by using a numerical rating scale. Results The training, validation, nonmisregistration test, and misregistration test data sets included 10 751, 2784, 1346, and 711 paired images collected from 40 patients (mean age, 62 years ± 11 [standard deviation]; 33 women). In the quantitative evaluation, DL-generated angiograms showed a mean PSNR value of 40.2 dB ± 4.05 and a mean SSIM value of 0.97 ± 0.02, indicating high coincidence with the paired DSA images. In the visual evaluation, the median ratings of the DL-generated angiograms were similar to or better than those of the original DSA images for all 24 sequences. Conclusion The deep learning-based model provided clinically useful cerebral angiograms free from clinically significant artifacts directly from dynamic angiograms. Published under a CC BY 4.0 license. Supplemental material is available for this article.

Incidental finding of neurosyphilis with intracranial hemorrhage and cerebral infarction: A case report.

Syphilis has recently increased in prevalence in Japan. Neurosyphilis is a special pathological condition of syphilis well known to cause cerebral vasculitis and ischemic stroke. Neurosyphilis in the meningovascular stage rarely causes caliber irregularity of the cerebral blood vessels or cerebral hemorrhage. We describe the case of a 49-year-old Japanese man with neurosyphilis. Cerebral hemorrhage, multiple cerebral infarctions, and caliber irregularity of the cerebral blood vessels were observed, the patient underwent surgery for cerebral hemorrhage on the day of admission, all of which were suspected to be caused by syphilis. He was started on an antibacterial treatment of penicillin on the day of admission and was diagnosed with neurosyphilis the following week based on his serum and spinal fluid test results. His condition improved, and he was transferred to another hospital after 4 weeks of treatment consisting of 3 weeks of infusion treatment with benzylpenicillin followed by oral treatment with amoxicillin. To the best of our knowledge, this is a rare case of neurosyphilis in conjunction with cerebral hemorrhage and cerebral infarction. Clinicians should consider syphilis in the differential diagnosis of cerebral hemorrhage and cerebral infarction and test patients for sexually transmitted diseases, in addition to cerebrospinal fluid testing, when cerebral hemorrhage occurs with an unknown cause. This is especially pertinent when patients present with cerebral infarction or caliber irregularity of the cerebral blood vessels.

Safe maximal resection of primary cavernous sinus meningiomas via a minimal anterior and posterior combined transpetrosal approach.

OBJECTIVE Meningiomas arising from the cavernous sinus (CS) continue to be a significant technical challenge, and resection continues to carry a relatively higher risk of neurological morbidity in patients with these lesions because of the tumor's proximity to neurovascular structures. The authors report the surgical outcomes of 9 patients with primary CS meningiomas (CSMs) that were surgically treated using a minimal anterior and posterior combined (MAPC) transpetrosal approach, and they emphasize the usefulness of the approach. METHODS This retrospective study included 9 patients who underwent surgery for CSM treatment between 2015 and 2016 via the MAPC transpetrosal approach. Two patients were men and 7 were women, with a mean age of 58.5 years (39-72 years). Five patients (55.5%) had undergone previous treatment. The surgical technique consisted of a temporo-occipito-suboccipital craniotomy and exposure of the posterolateral part of the CS via the presigmoidal MAPC approach. After opening Meckel's cave and identifying the 3rd-5th cranial nerves in the prepontine cistern, Parkinson's triangle and supratrochlear triangles were opened. Finally, the tumor occupying the posterolateral part of the CS was removed. RESULTS All lesions were safely and maximally removed, with preservation of external ocular movements and preoperative Karnofsky Performance Scale scores. The mean extent of resection was 77.0% (range 58.7%-95.4%). Six patients underwent adjuvant therapy in the form of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) during the follow-up period; none of these patients experienced recurrence. CONCLUSION The authors conclude that the MAPC transpetrosal approach could be superior to other approaches for CSMs, as it provides direct visual access to the posterolateral portion of the CS. In their experience, this approach is an alternative and better option for safe maximal resection of CSMs.

Schwannoma-like tumor in the anterior cranial fossa immunonegative for Leu7 but immunopositive for Schwann/2E.

Schwannoma arising from the olfactory system, often called olfactory groove schwannoma (OGS), is rare, as the olfactory bulb and tract, belonging to the central nervous system, should lack Schwann cells. Another rare entity called olfactory ensheathing cell tumor (OECT) has been reported, which mimics clinical and radiological characteristics of OGS. Here, we report two rare cases of schwannoma-like tumor in the anterior cranial fossa that showed negative staining for Leu7, but positive staining for Schwann/2E, and discuss their origin. Two cases of mass lesions in the anterior cranial fossa in a 26-year-old man and a 24-year-old woman were successfully removed. Morphological examination of these tumors was compatible with a diagnosis of schwannoma. Immunohistochemically, both cases were negative for Leu7, yielding a diagnosis of OECT, but were positive for the schwannoma-specific marker, Schwann/2E. Immunohistochemical staining results in our two cases question the current assumption that OGS and OECT can be distinguished only by Leu7 staining pattern. In conclusion, the origins of OGS and OECT remain to be determined, and further studies in larger numbers of cases are needed to characterize these rare tumors in the anterior cranial fossa.

Characteristic of optic canal invasion in 31 consecutive cases with tuberculum sellae meningioma.

Optic canal invasion by tuberculum sellae meningiomas (TSMs) has been reported, but the characteristics of invasion remain unclear. This study was performed to clarify the incidence and characteristics of optic canal invasion by TSM and to determine whether optic canal invasion could be predicted preoperatively by magnetic resonance imaging (MRI). Between February 2002 and August 2014, 31 patients with TSM underwent tumor resection in our institute. In all cases, the optic canal was explored to identify any tumor invasion. We classified the characteristics of optic canal invasion from intraoperative findings. Invasion was classified into four types: type 1: no invasion; type 2: secondary invasion; type 3: partial wall invasion (two subtypes); and type 4: invasion into the supero-medial-inferior walls of the optic canal. Thirty of 31 cases showed optic canal invasion. Of these 30 cases, 9 (30 %) showed bilateral optic canal invasion. The most common finding was type 1 (23 sides). Among cases with optic canal invasion (39 sides), type 4 was the most common pattern (17 sides), followed by type 3-infero-medial (13 sides), type 2 (5 sides), and type 3-supero-medial (4 sides). Blinded prediction of tumor invasion was accurate in 61 % of cases, but characteristics of tumor invasion were undeterminable from preoperative MRI. In conclusion, optic canal invasion was frequently seen in our consecutive series of TSM, characteristics of which were unpredictable preoperatively. Neurosurgeons should be aware of the high incidence and variety of optic canal invasion in planning strategies for TSM treatment.

Aggressive surgery based on an anatomical subclassification of craniopharyngiomas.

OBJECTIVE Craniopharyngiomas remain a particularly formidable challenge in the neurosurgical field. Because these lesions involve the hypothalamus and ophthalmological systems, their resection is associated with either higher rates of mortality and recurrence or a lower rate of radical resection. The authors report the outcomes of aggressive surgeries based on an anatomical subclassification of craniopharyngiomas. METHODS Clinical and ophthalmological examinations, imaging studies, endocrinological studies, neuropsychological function, and surgical complications in all patients who had undergone microsurgical resection for craniopharyngioma at Osaka City University hospital between January 2000 and December 2014 were retrospectively reviewed through the medical records. Radical resections were planned in all of the patients. To help choose the correct surgical approach, craniopharyngiomas were classified based on tumor origin. The 4 possible groups included the intrasellar type, prechiasmatic type, retrochiasmatic type, and intra-third ventricle type. A multistage surgery was planned in some cases. RESULTS Seventy-two cases of craniopharyngioma were resected. Thirty-two patients (44.4%) had undergone previous surgical procedures at other institutions. Thirty-five cases (48.6%) were classified as retrochiasmatic, 19 (26.4%) as prechiasmatic, 12 (16.7%) as intra-third ventricle, and 6 (8.3%) as intrasellar. In 26 cases (36.1%), multistage surgery was required to complete the radical resection. Overall, 41 cases involved an orbitozygomatic approach; 21, a transpetrosal approach; 21, an interhemispheric approach; and 14, a transsphenoidal approach. In 3 cases, other approaches were applied. Gross-total resection was achieved in 43 patients (59.7%), near-total resection in 28 (38.9%), and partial resection in only 1 patient (1.4%). The mean follow-up period after resection was 4.7 years. Tumor recurrence or regrowth occurred in 15 (20.8%) of the 72 patients, with 14 of the 15 cases successfully controlled after additional resections and stereotactic radiosurgery. However, 1 patient died of uncontrollable tumor progression, and 2 patients died of unrelated diseases during the follow-up. Overall, disease in 69 (95.8%) of 72 patients was well controlled at the last follow-up. CONCLUSIONS Aggressive tumor resection is the authors' treatment policy for craniopharyngioma. Using an anatomical subclassification of craniopharyngioma to choose the most appropriate surgical approach is helpful in achieving that goal of aggressive resection.

Staged 'intentional' bridging vein ligation: a safe strategy in gaining wide access to skull base tumors.

BACKGROUND: The venous drainage of the temporal lobe, through bridging veins to the middle cranial fossa, is pivotal in determining the surgical corridor for skull base lesions. In dealing with select cases, where venous drainage was an obstacle in the surgical approach, we hypothesized that staged 'intentional' ligation of the dominant pathway of venous drainage would provide a safer and wider access to skull base tumors. We study the indications and safety of this surgical strategy in the management of skull base lesions. MATERIALS AND METHODS: From 1995 to 2012, 318 patients with skull base tumors were treated at our institute by the fronto-orbito-zygomatic (FOZ) or transpetrosal approaches, eight of whom we planned for staged 'intentional' bridging vein ligation. Seven patients underwent planned ligation of the bridging veins from the temporal lobe to the middle cranial fossa floor in the first stage, followed by definitive surgery through the desired skull base approach, in the second stage, while in one patient the strategy was abandoned. These patients were evaluated with respect to their clinical presentation, pre- and post-operative radiology including venogram, intra-operative findings and post-operative course. RESULTS: Seven patients, four males and three females, with ages ranging from 16 to 63 years, underwent staged 'intentional' bridging vein ligation. The diagnoses were recurrent craniopharyngioma in four, and petroclival meningioma, sphenopetroclival meningioma and spheno-orbital meningioma in one each. Six of these lesions were approached from the dominant (left) side, while one lesion was on the right side. Venograms done after the first-stage procedure showed obliteration of the dominant venous drainage with opening up of anastomotic venous channels in all patients. All patients tolerated the first-stage procedure well; only one patient showed asymptomatic mild temporal lobe edema on MRI, which resolved in 3 weeks. None of the patients had venous complications after definitive surgery. One patient with recurrent chordoma, who was planned for staged ligation, did not undergo ligation as, intra-operatively, the draining channel turned out to be a cortical vein, which could be mobilized without ligation. CONCLUSION: In an attempt to detether the temporal lobe, the disconnection of the bridging veins from the temporal lobe to the middle cranial fossa floor in the first stage may lead to re-direction of the venous outflow over time. This may allow skull base surgeons a better surgical corridor and ensure safety of venous structures during the definitive surgery.