Gamma Knife Irradiation Research Articles

Large cell neuroendocrine carcinoma of the gallbladder: long survival achieved by multimodal treatment

Large cell neuroendocrine carcinoma of the gall-bladder is a rare disease in which the prognosis worsens with size. We report a case of large cell neuroendocrine carcinoma of the gallbladder in a 64-year-old woman who presented with a right upper quadrant mass whose longest diameter was 11.5 cm; the mass was initially considered to be unresectable because of probable invasion to the main portal vein and biliary tract. The patient received multi-modal treatment, consisting of intraarterial chemotherapy, three-dimensional radiation therapy, right trisegmentectomy, and gamma-knife irradiation (for brain metastases). She has survived for 69 months since the initial diagnosis and has shown no signs of recurrence at 35 months after the last gamma-knife irradiation for brain metastases. This result suggests that multimodal treatment including surgery, chemotherapy, and radiation therapy achieved a good response and led to long survival.

A dosimetric evaluation of tissue equivalent phantom prepared using 270 Bloom gelatin for absorbed dose imaging in Gamma knife radiosurgery

Tissue equivalent gel phantoms have been widely studied in radiation therapy for both relative and reference dosimetry. A Fricke xylenol gel (FXG) spherical phantom was evaluated by means of magnetic resonance image method (MRI) to measure absorbed dose distribution resulted from gamma knife irradiation. The FXG phantom was prepared using 270 Bloom gelatin. The gelatin is a tissue equivalent material, of easy preparation, can be used to mold phantoms into different shapes and volumes, is commercially available and inexpensive. The results show that the Fricke gel phantom prepared with 270 Bloom gelatin satisfy the requirements to be used for the quality control in stereotactic radiosurgery using Gamma Knife technique and may constitute one more option of dosimeter in radiation therapy applications.

Gamma Knife relative dosimetry using VIP polymer gel and EBT radiochromic films

The VIP polymer gel–MRI method and EBT Gafchromic films were employed to obtain relative dosimetry results for the Gamma Knife (GK) radiation fields of 4 mm and 18 mm nominal diameter. Results are compared to the corresponding calculations of GammaPlan Treatment Planning System (TPS) in the form of 1D profiles and 2D distributions. Measured and planned relative dosimetry datasets are found in close agreement within experimental uncertainties. A corresponding agreement is shown for Dose Volume Histogram (DVH) results that are available only through the application of the polymer gel method.

GAMMA KNIFE RADIOSURGERY–INDUCED CAVERNOUS HEMANGIOMA

Abstract OBJECTIVE We report a rare case of gamma knife radiation–induced cavernous hemangioma. CLINICAL PRESENTATION A 35-year-old man underwent resection of a left vestibular schwannoma and gamma knife radiosurgery (maximal dose, 24 Gy; marginal dose, 12 Gy) for the residual schwannoma. Follow-up magnetic resonance images showed no tumor progression. Ten years later, he developed right hemihyperesthesia and mild hemiparesis. Magnetic resonance imaging revealed a size reduction at the resected tumor site and a newly developed lesion in the adjacent pons. No connection was observed between the new mass and the previous tumor. The T2-weighted image showed the new mass as heterogeneous and “popcorn-like” with a mixed signal intensity core and a hypointense hemosiderin rim. Two years after its appearance, the new lesion appeared hypointense on the T2-weighted image, with a hyperintense core on the T1-weighted image. These findings were compatible with cavernous hemangioma. INTERVENTION We diagnosed the new lesion as a radiation-induced cavernous hemangioma. Ten days after admission, symptoms improved without surgical intervention. CONCLUSION Gamma knife radiosurgery induced this rare case of cavernous hemangioma in an area that received a low dose of irradiation and was distant from the primary tumor. Because patients undergoing radiosurgery face the possibility, although small, that such neoplasms may occur, they should be followed for many years.

Experimental Analysis of Radiation Dose Distribution in Radiosurgery: I. Dose Hot Spot inside Target Volume

Introduction: Radiosurgery is currently performed with different systems of focused radiation providing different dose heterogeneities within the target volume. Here, we aimed to study histological consequences of different dose distributions inside the target area in an experimental model of Gamma Knife irradiation in the rat striatum. Material and Methods: Twelve rats were irradiated by Gamma Knife at the same volume in the right striatum; the same margin dose of 45 Gy was prescribed for all rats. Three different dose distributions inside the target volume were applied. Brain sections at the level of the target area were histologically analyzed 3 months after irradiation. Results: Of the 7 histopathological reactions found as a consequence of the irradiation, 6 of them were significantly related to the gradient of dose heterogeneity within the target volume. Conclusions: Dose distribution inside the target volume could influence the histological effects of radiosurgical irradiation on tissue included in the target. A high dose in the target volume is more likely to lead to the desired radiobiological result.

Treatment strategy of pituitary invasive prolactinomas

To discuss the treatment strategy of invasive prolactinomas (IPs) involving the cavernous sinus. Data from 80 patients with IPs treated in our institutions were reviewed retrospectively. The criteria utilized included: (1) invasion of the cavernous sinus by tumor, corresponding to Grade III-IV according to the classification of Knosp; (2) serum prolactin level > 9.1 nmol/L; (3) clinical signs of hyperprolactinemia and mass effect. Among the 80 patients who met the criteria: 21 patients received bromocriptine as primary treatment (Group A); 21 patients initially received bromocriptine and then accepted microsurgery or irradiation (Group B); 38 patients had initially undergone transcranial or transsphenoidal microsurgery and then received bromocriptine or adjuvant radiotherapy (Group C). Eleven patients underwent gamma knife radiotherapy. In 57 patients (12 cases of Group A, 16 cases of Group B, 29 cases of Group C), the tumors on MRI had almost completely disappeared after an average follow-up period of 62 months, and in the other 23 patients, residual tumor involved the cavernous sinus. Visual symptoms improved in 33 patients while deteriorated in 7 patients. Serum prolactin level of 52 patients had in normal range after treatment (10 cases of Group A, 11 cases of Group B, 31 cases of Group C) and 7 patients were more than 9.1 nmol/L. Nine patients had symptoms of hypopituitarism. For IPs, individualized treatment methods are advocated in which dopamine agonist medications are effective as first-line therapy. It is necessary to take dopamine agonist after operation and close observation is mandatory. Gamma knife surgery is an option to treat the residual tumor involving the cavernous sinus.

Oculopalatal tremor and severe late-onset cerebellar ataxia

Following four recurrent bleedings of a mesencephalic cavernoma within 10 years (figure 1A), a 62-year-old woman demonstrated left kinetic cerebellar syndrome. She then developed oculopalatal tremor (OPT) associated with bilateral inferior olive hyperintensity (figure 1B). Gamma knife radiation was performed, but she developed severe cerebellar ataxia. OPT secondary to brainstem strokes and …

SU‐GG‐T‐449: Peripheral Dose Investigation of a Corpus Collosotomy by Gamma Knife, Model C

Purpose: Corpus collosotomy by Gamma Knife Radiotherapy is a treatment for medically refractory epilepsy. Due to the long treatment duration (3–6 hours), the peripheral dose received by patients becomes a concern. In this study, peripheral doses for a posterior corpus collosotomy by Gamma Knife, Model C were investigated. Method and Materials: A Rando‐Phantom was used to measure the peripheral doses. Three types of dosimetry systems were used, which included ionization chambers, TLDs (TLD‐100 3×3×1mm chips), and OneDose™ MOSFET dosimeters. The dosimeters were placed on the surface of the Rando‐Phantom under 0.5 cm of build up at distances of 5.0, 17.5, 30.0, 42.5, 54.0, 70.0 and 84cm from the center of the treatment volume. Seven cylindrical ionization chambers with buildup caps were placed at the same distances, one chamber at each position. The leakage of the ionization chambers was measured before irradiation and recorded during treatment sessions. The phantom was irradiated using a clinical treatment plan for a posterior corpus collosotomy. The prescription dose was 130Gy (max dose), and the delivery dose was reduced to one third of the prescription dose for measurement purposes. The treatment time was 99.38 minutes. Results: The measured doses by TLD were 17.9, 9.9, 5.8, 2.9, 2.4, 1.5, and 1.1cGy for the seven positions respectively. The measured doses by ionization chambers were 16.9, 12.0, 5.2, 2.9, 2.8, 2.2, and 2.0cGy. The results obtained with the OneDose™ were not consistent due to the decay of the signal over the period of measurement. The doses measured by TLD and ionization chamber for the same position were averaged. The total doses to the measurement positions were 52.2, 33.0, 16.5, 8.7, 7.8, 5.7, and 4.8cGy, respectively, for the full prescription dose of 130Gy. Conclusion: The peripheral doses were significant, especially in the head and neck region.

SU‐GG‐T‐296: A Method for Removing An Artifact in Time‐Dependent Dose Rate Data Obtained with An Ionization Chamber

Purpose: To develop an algorithm to remove the RC‐like artifact with time‐dependent dose‐rate measurements using an ionization chamber and electrometer system. Method and Materials: A 0.07‐cc Farmer‐type ionization chamber, Capintec Model PR05‐P, was used for dose measurements. The electrometer was Standard Imaging MAX‐4000, which was connected to a laptop computer. Electrometer control software, a special version of the MAXcomm program, was used to sample the electric current readings every 100 msec. We formulated a rate equation for the number of electrons in the cavity by hypothesizing that the RC‐like artifact is caused by the finite time needed for electrons to recombine with ions in the cavity of the ionization chamber. The rate equation includes terms for the ionization, the loss of electrons due to two‐body recombination, and the loss of electrons due to the electrons flowing out from the chamber cavity to the electrometer. The unknown parameters in the equation were obtained by iteratively adjusting the values until we achieved the best fit of the corrected ionization current data with the ideal time‐dependent ionization current curve. For the parameter estimation, we used the data of one 100MU irradiation of a linac photon beam. Next, the correction algorithm with the estimated parameter values was applied to the time‐dependent dose‐rate data obtained for a test case of Gamma Knife irradiation. Results: By iteratively adjusting the values of the two parameters in the rate equation, we could recover the ideal rectangular shaped beam pulse of the linac photon beam. Using these parameters, the temporal variation of the ionization current for the Gamma Knife experiment was successfully corrected by removing the RC‐like artifact. Conclusion: The proposed method is capable to eliminate the artifact in the time‐dependent dose‐rate measurements.

Effects of gamma knife irradiation on the expression of NMDA receptor subunits in rat forebrain

To examine the effects of gamma knife surgery (GKS) on the expression of N-methel-D-asparate receptor (NMDAR) subunits in rat forebrain. Using stereotactic technique, we performed gamma knife irradiation on the left forebrain of 13 male Wistar rats with a maximum dose of 60 Gy. These animals were raised for 24h, 30 and 60 days before they were killed. Then immunohistochemistry was applied to detect the relative levels of NMDAR subunits (NR1, NR2A, and NR2B) in the target region. The expression of NR1 and NR2A but not NR2B increased significantly in the cortex 30 and 60 days after irradiation. However, no significant differences in the expression of these three subunits were detected in the caudate putamen at all time points. gamma knife irradiation induced the upregulation of NMDAR subunits, NR1, and NR2A, which might represent a possible mechanism underlying the therapeutic effects of gamma knife irradiation on many neurological diseases, including drug resistance epilepsy.

A case of gastric cancer with isolated brain metastasis successfully managed by gamma knife radiotherapy and chemotherapy

A case of gastric cancer with isolated brain metastasis successfully managed by gamma knife radiotherapy and chemotherapy

Development of a Stereotactic Device for Gamma Knife Irradiation of Small Animals

The authors developed a stereotactic device for irradiation of small animals with Leksell Gamma Knife(R) Model C. Development and verification procedures were described in this article. The device was designed to satisfy three requirements. The mechanical accuracy in positioning was to be managed within 0.5 mm. The strength of the device and structure were to be compromised to provide enough strength to hold a small animal during irradiation and to interfere the gamma ray beam as little as possible. The device was to be used in combination with the Leksell G-frame(R) and KOPF(R) rat adaptor. The irradiation point was determined by separate imaging sequences such as plain X-ray images. The absolute dose rate with the device in a Leksell Gamma Knife was 3.7% less than the value calculated from Leksell Gamma Plan(R). The dose distributions measured with GAFCHROMIC(R) MD-55 film corresponded to those of Leksell Gamma Plan(R) within acceptable range. The device was used in a series of rat experiments with a 4 mm helmet of Leksell Gamma Knife. A stereotactic device for irradiation of small animals with Leksell Gamma Knife Model C has been developed so that it fulfilled above requirements. Absorbed dose and dose distribution at the center of a Gamma Knife helmet are in acceptable ranges. The device provides enough accuracy for stereotactic irradiation with acceptable practicality.

CLINICAL RELEVANCE OF PRECIPITATING FACTORS IN PITUITARY APOPLEXY

The pathogenesis of pituitary apoplexy and the role of precipitating factors in pituitary apoplexy are poorly understood. Most of the published cases are in the form of case reports. We assessed the presumed precipitating factors in a series of patients treated surgically for pituitary apoplexy and reviewed the contemporary published literature. Thirty-eight consecutive patients with pituitary apoplexy were treated surgically by the Department of Neurosurgery at the University of Virginia, Charlottesville, VA, between January 1996 and March 2006. Their medical records were retrospectively reviewed. Contemporary published cases from 1990 to 2006 were also reviewed. Nine patients (24%) were identified as having precipitating factors for pituitary apoplexy. The factors identified were coronary artery surgery (two patients), other major surgery (two patients), pregnancy (two patients), gamma knife irradiation, anticoagulant therapy, and coagulopathy secondary to liver failure. The presentation, histology, and outcome were compared between those patients with a precipitating factor and those in whom none was identified. A review of the published literature showed that coronary artery surgery, pituitary stimulation, and coagulopathy were the most common precipitating factors. A minority of patients with pituitary apoplexy will have precipitating factors. The majority of patients with precipitating factors will have histopathology showing hemorrhagic infarction or hemorrhage. The most common precipitating factors are pituitary stimulation, surgery, particularly coronary artery surgery, and coagulopathy. Caution in doing endocrine investigation, surgery, or anticoagulation in patients with a known pituitary tumor is advised. Patients with no diagnosed pituitary tumor but with a known precipitating factor who have neuro-ophthalmological deterioration or endocrine failure should undergo prompt magnetic resonance image scans and endocrine investigation and endocrine replacement as indicated.

TU‐EE‐A1‐02: Whole Procedure Accuracy of Gamma Knife Radiosurgery of Large Tumors Via Multiple Isocenter Delivery

Purpose: Geometric accuracy of single‐isocenter Gamma Knife delivery has been well established to within 0.3 mm. The question frequently asked is the accuracy of the full‐procedure Gamma Knife treatments, particularly important for large tumors requiring multiple isocenter deliveries. In this study, we performed direct measurements to determine such accuracy. Method and Materials: An anthropomorphic head phantom with a central spherical target of 3.0 cm in diameter was employed for measurements. We placed the stereotactic frame on the phantom and followed identical imaging and treatment protocols for treatment planning and beam delivery. CT scans of varying slice thicknesses of 1 mm, 2 mm and 3 mm were acquired and used for treatment planning calculations. The phantom was irradiated using 16 isocenters delivered with Gamma Knife automatic patient positioning system (APS). Radiochromic films aligned with the center of the target were exposed. The isodose measurements were compared with the 3D dose calculations from the treatment planning system (Leksell GammaPlan Wizard 4C). Results: The overall agreements were found to be approximately 2 mm between the measurements and dose calculations. The agreement was slightly better (approximately 1.5 mm) for the peripheral isodose line (e.g., 50% of the maximum dose) but deteriorated significantly (2–4 mm) for low (e.g., 30% of the maximum dose) or high isodose lines (e.g., 80% of the maximum dose). The 2‐mm dose accuracy showed no dependence on the slice thickness of the CT studies. The 2mm overall accuracy is closely matched the dose grid box resolution of 1.8 mm that was needed to encompass the full target volume for calculations. Conclusion: Overall accuracy of Gamma Knife irradiation of a large target was found to be approximately 2 mm, regardless the slice thickness of acquired images. The dose grid resolution was likely the dominant factor contributing to this result.

A rare case of extraventricular neurocytoma

We report an unusual case of extraventricular (cerebral) neurocytoma with a long, 25-year history, and which appeared to transform to neuroblastoma. In 1978, an 18-year-old woman was treated for right frontal oligodendroglioma. Eighteen years later (in 1996), recurrence of tumor in the fourth ventricle was noted and was treated with gamma-knife radiotherapy. The tumor shrunk transiently, but 7 years later (in 2004), MRI study demonstrated a second recurrence and ventricular dissemination. Partial removal was performed, and histological examination revealed that tumor cells had round or oval nuclei with halos. Frequent mitoses and vascular proliferation were observed. The MIB-1 LI was 80%. Despite postoperative whole-brain radiotherapy to a total dose of 30 Gy, the tumor progressed, and she died at 4 months after the second surgery.

A 46-year-old woman with severe weakness following acute respiratory distress syndrome

A 46-year-old woman was seen for severe generalized weakness following acute respiratory distress syndrome. The patient had been reviewed earlier at Mayo Clinic in June 1998 for a new-onset generalized seizure and at that time was diagnosed with a glioblastoma multiforme of the left temporal lobe. She was treated with gross total resection of the tumor followed by radiation therapy and chemotherapy with carmustine. In April 1999, due to the progression of the tumor, she had a subtotal tumor resection and was started on irinotecan. In June 1999, there was further tumor growth and she was treated with gamma knife radiation therapy followed by four cycles of chemotherapy with paclitaxel and oral corticosteroids with an average daily dose of 2 mg per day of dexamethasone. In early December 1999, she became febrile with a presumed sinus infection. Shortly after that she was hospitalized at an outside institution for progressive dyspnea. An extensive workup that included V/Q lung scan, helical chest CT, echocardiogram, and a Doppler study of both lower limbs was unremarkable. She was noted to have a necrotic lesion of the left breast which grew Pseudomonas aeruginosa , and was started on IV piperacillin tazobactam. Blood cultures were negative. While hospitalized, she rapidly developed severely worsened dyspnea and required oxygen supplementation by a nonrebreather mask and was therefore transferred to Mayo Clinic. On initial evaluation, she was severely hypoxemic with 64% oxygen saturation and was transferred immediately to the medical intensive care unit for intubation and ventilatory support. She was diagnosed with adult respiratory distress syndrome. She was sedated with propofol and fentanyl and received inotropic support with dopamine. She continued to receive IV antibiotics, was started on 200 mg IV methylprednisolone per day, and was fed by a nasogastric tube. Her medications on evaluation in the medical intensive …

Inhibition of angiogenesis induced by cerebral arteriovenous malformations using Gamma Knife irradiation

The authors studied the effect of Gamma Knife irradiation on angiogenesis induced by cerebral arteriovenous malformation (AVM) tissues implanted in the corneas of rats. Ten AVM specimens obtained from tissue resections performed at Marmara University between 1998 and 2004 were used. A uniform amount of tissue was implanted into the micropocket between the two epithelial layers of the cornea. Gamma Knife irradiation was applied with dose prescriptions of 15 or 30 Gy to one cornea at 100% isodose. Dosing was adjusted so that the implanted cornea of one eye received 1.5 Gy when 15 Gy was applied to the other cornea. Similarly, one cornea received 3 Gy when 30 Gy was applied to the other cornea. Angiogenic activity was graded daily by biomicroscopic observations. Forty-eight other rats were used for microvessel counting and vascularendothelial growth factor (VEGF) staining portions of the experiment. Micropieces of the specimens were again used for corneal implantation. Rats from each group were killed on Days 5, 10, 15, and 20, and four corneas from each group were examined. Gamma Knife irradiation dose dependently decreased AVM-induced neovascularization in the rat cornea as determined by biomicroscopic grading of angiogenesis, microvessel count, and VEGF expression. The results suggest that Gamma Knife irradiation inhibits angiogenesis induced by AVM tissue in the cornea angiogenesis model. The data are not directly related to understanding how Gamma Knife irradiation occludes existing AVM vasculature, but to understanding why properly treated AVMs do not recur and do not show neovascularization after Gamma Knife irradiation.

Gamma Knife Radiosurgery Targeting Protocols for the Experiments with Small Animals

Background/Aims: Manipulation of brain functions via Gamma Knife (GK) irradiation would have numerous applications in clinical and experimental neurology. Methods: Alteration of brain functions in the unilaterally irradiated striatum was indexed through monitoring freely moving rat behaviors. Spontaneous activity and rotations on the apomorphine test, which can detect dopaminergic function imbalance, were indexed employing our behavior tracking system. The spatial distribution of necrotic lesions was explored using serial sections, and was assumed to represent the real foci of the GK target. Results: Distinct behavioral alterations corresponded to the precise locations of the lesions in various areas of the basal ganglia. Displacement of the irradiation sites in the anteromedial direction increased spontaneous activity, and posterolateral shift provoked circling behavior on the apomorphine test. Conclusion: Accurate positioning of the target is crucial for experimental GK irradiation locally focused on domains of a small brain such as that of the rat. Here, we propose a protocol for converting the ‘intended’ focus, based on brain map coordinates, to a ‘planned’ focus on the MR imaging coordinate system with the Régis-Valliccioni stereotactic frame.

Clinicopathologic findings in mesial temporal sclerosis treated with gamma knife radiotherapy

Mesial temporal sclerosis (MTS) is the most common cause of medically intractable temporal lobe epilepsy. Histologic findings include hippocampal atrophy with neuronal loss in the dentate, CA1, and CA3/CA4 regions with gliosis. The conventional treatment of patients with intractable epilepsy secondary to MTS has been surgical excision. Gamma knife radiotherapy (GKR) has recently been suggested as a less invasive alternative to surgery. To date, the histologic changes that occur in this setting after GKR have not been well described. The clinicopathologic features of 4 patients with MTS who received GKR and underwent subsequent surgical resection or autopsy were retrospectively reviewed. The study group is composed of 4 patients (3 women, 1 men) with ages 55, 48, 22, and 20 years, respectively, at the time of GKR. There were 2 patients who had a history of infantile febrile seizures, and 2 who had a central nervous infection during infancy. All 4 patients had a long-standing (13-36 years) history of temporal lobe seizures resistant to medical management. Imaging studies, electroencephalogram, and surgical specimens all confirmed the diagnosis of MTS. The oldest of the 4 patients died 1 month after receiving GKR, presumably because of post-gamma knife persistent seizure complications. The postmortem neuropathology on this patient was unremarkable for any radiation effect changes but showed evidence of MTS. The remaining 3 patients underwent surgical resection for persistent seizures at 18, 22, and 20 months, respectively, post-gamma knife. These 3 surgical specimens showed variable degrees of radiation effect changes in the temporal lobe, hippocampus, and amygdala, including chronic (lymphocytes and macrophages) perivascular inflammation (3/3), vascular sclerosis (3/3), foci of edema with necrosis (3/3; extensive in 2 patients), reactive astrocytosis (3/3), microglial proliferation (1/3), and microcalcifications (1/3). Patients with MTS who underwent GKR can develop typical radiation changes over time. Treatment of individuals with MTS via GKR may not always be adequate in controlling seizures. Radiation therapy effect may contribute to persistent seizures after GKR in some patients with MTS.

Expanded endonasal approach: a fully endoscopic completely transnasal resection of a skull base arteriovenous malformation

Vascular lesions with an intraosseus nidus involving the skull base are uncommon and challenging [Gianoli GJ, Amedee RG Vascular malformation of the sphenoid sinus. Ear Nose Throat J. 70:373-375;(1991), Malik GM, Mahmood A, Mehta BA Dural arteriovenous malformation of the skull base with intraosseous vascular nidus. Report of two cases. J. Neurosurg 81:620-623;(1994)]. We present a pediatric patient, with a life-threatening arteriovenous malformation (AVM) of the sphenoid sinus, clivus, and ventral skull base, who failed routine multimodality management of AVMs. An entirely transsphenoidal fully endoscopic resection was used to resect this ventral cranial base AVM with an intraosseus nidus located in the clivus. A 4-year-old female presented with recurrent, life-threatening hemorrhages from a clival and ventral skull base AVM of the entire clivus and ventral skull base. The patient had been temporized from the age of 2-4 years with multiple internal and external carotid arterial particulate and alcohol embolizations, including both external and internal carotid artery embolizations, intracranial ligation of the right internal carotid artery, and gamma knife irradiation. Despite these multiple interventions, the patient had persistent, life-threatening hemorrhages from arterial recanalization and recruitment requiring intubation, tracheostomy, and nasopharyngeal packing. The patient underwent a three-stage surgical intervention to resect the AVM. An open subfrontal approach, as the first procedure, provided minimal access to the feeding vessels and was therefore aborted. A two-stage image-guided fully endoscopic approach via a sublabial midface approach without external incisions was performed. Postoperative angiography revealed minimal residual shunting in the pharynx and cavernous sinus. The patient has been free of significant hemorrhages over the past three years. Technological advances in endoscopic surgery and image guidance are now allowing for purely endoscopic surgical treatment of previously unresectable lesions with acceptable morbidity. We report the successful and safe resection of a ventral cranial base AVM via a fully endoscopic approach. This paper reports the first AVM with a purely intraosseus nidus of the ventral skull base and demonstrates the ability to deal with complex ventral skull base lesions using a fully endoscopic transsphenoidal technique.