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Background There is little information on long-term outcomes after salvage treatment by either surgery or stereotactic radiosurgery (SRS) for patients with recurrent/residual nonfunctioning pituitary adenomas (NFPAs). Objective To reappraise the efficacy and safety of SRS for patients with NFPAs touching/compressing the optic apparatus (OA). Methods We studied 27 patients (14 females, 13 males; mean age: 61 [range, 19-85] yr) who underwent SRS between 1998 and 2008 for NFPAs with such condition. The median tumor volume was 4.9 (range, 1.8-50.8) cc. To avoid excess irradiation to the OA, the lower part of the tumor was covered with a 50% or a 60% isodose gradient, ie 49% to 98% (mean, 84%; median, 88%) of the entire tumor received the selected doses. Median doses at the tumor periphery/OA were 7.6/11.0 (interquartile range [IQR], 5.8-9.1/10.1-11.8) Gy. Results Seven patients (26%) were confirmed to be deceased due to unrelated diseases at a median post-SRS period of 149 (IQR, 83-158) mo. Follow-up magnetic resonance imaging (MRI) showed tumor growth in 2 patients (7%) at the 11th and 134th post-SRS month; the former underwent surgery and the other SRS. Excluding these 2 patients, the latest follow-up MRI examinations, performed 13 to 238 (median: 168, IQR: 120-180) mo after SRS, showed no size changes in 5 (19%) and shrinkage in 20 (74%) patients. Cumulative incidences of tumor growth control were 96.3% and 91.8% at the 120th and 180th post-SRS month. None of our patients developed subjective symptoms suggesting SRS-induced optic neuropathy or endocrinological impairment. Conclusion In patients with NFPAs touching/compressing the OA, SRS achieves good long-term results.

Background The supraorbital keyhole approach has been used in anterior skull base tumor and aneurysm surgery. However, there are debates regarding the safety and limitations of this kind of approach. Objective To determine the feasibility and potential benefits of surgical robotic technology in minimally invasive neurosurgery. Methods Two fresh cadaver heads were studied with the da Vinci Surgical System with 0° and 30° stereoscopic endoscopes to visualize neuroanatomy. The ability of the system to suture and place clips under the keyhole approach was tested. Results The da Vinci Surgical System was used throughout the supraorbital transeyebrow keyhole approach. With the use of standard microdissection techniques, the optic nerve, optic chiasm, carotid artery, and third cranial nerve were visualized. The sylvian fissure was then exposed from the proximal sylvian membrane to the distal M1 segment. With the EndoWrist microforceps, suturing can be achieved smoothly to close a defect created on the M2 artery. Although the benefits in adjusting clips during aneurysm surgery could be provided by an articulating applier, a proper robotic applier is not currently available. Conclusion The minimally invasive supraorbital keyhole surgery can be achieved with the da Vinci Surgical System in cadaver models. This system provides neurosurgeons with broader vision and articulable instruments, which standard microsurgical systems do not provide. Further studies are necessary to evaluate the safety and benefits of using the da Vinci Surgical System in minimally invasive neurosurgery.

Background Various surgical approaches for the removal of tuberculum sellae meningiomas (TSMs) have previously been described. Objective To assess the reliability and safety of the lateral supraorbital (LSO) approach to remove TSMs. Methods We identified all TSM patients operated on at the Department of Neurosurgery at Helsinki University Central Hospital, Finland, by the senior author (J.H.) using the LSO approach between September 1997 and August 2010. We retrospectively analyzed the clinical data, radiological findings, surgical treatment, histology, and outcome of patients and discuss the operative technique. Results Apparent complete tumor removal was achieved in 45 patients (87%). Of 42 patients, preexisting visual deficit improved in 22, remained the same in 13, and worsened in 7, and de novo visual deficit occurred in 1 patient. At 3 months post-discharge, 47 patients (90%) had a good recovery, 4 (8%) were moderately disabled, and 1 (2%) died 40 days after surgery of unexplained cardiac arrest. Seven patients (13%) had minimal residual tumors, 2 of which required reoperation. During the median follow-up of 59 months (range, 1-133 months), tumor recurred in 1 of the patients who had undergone a second operation. Conclusion TSMs of all sizes can be removed via the LSO approach with minimal morbidity and mortality. Low-power or no coagulation is recommended near the optic nerves and the optic chiasm to preserve their vascular support from the internal carotid artery perforators. Our results are comparable to those obtained using more extensive and time-consuming approaches. We recommend the LSO approach to remove TSMs.

BACKGROUND: Rathke cleft cysts (RCCs), benign remnants of the Rathke pouch typically arising in the sella, sometimes have suprasellar extension. Purely suprasellar RCCs are rarely reported. OBJECTIVE: To compare the presentations, surgical outcomes, and pathology of purely suprasellar RCCs and sellar-based RCCs. METHODS: We retrospectively reviewed records, magnetic resonance images, laboratory results, and pathology of 151 RCC patients surgically managed at our institution from 1989 to 2009. The RCCs were classified as purely sellar (type I, n = 76), sellar with suprasellar extension (type II, n = 56), or purely suprasellar (type III, n = 19). RESULTS: The RCCs with a suprasellar component (types II and III) more commonly presented with visual dysfunction (P

Background and importance We present a rare case of a patient with intrasellar salivary gland-like pleomorphic adenoma and review the 2 previously reported cases of the clinical entity to identify their common clinical features. Clinical presentation A 56-year-old Asian man visited our hospital with a chief complaint of visual disturbance caused by brain tumor that filled up the sella turcica with suprasellar extension. The patient underwent craniotomy via a left pterional approach, and the subdural, intracranial portion of the tumor was totally removed, with every artery and nerve preserved. Pathological diagnosis of the tumor was intrasellar salivary gland-like pleomorphic adenoma. Three years after the operation, the patient remains free from tumor recurrence. Conclusion Tumors in all 3 reported cases of intrasellar salivary gland-like pleomorphic adenoma, including the present case, showed suprasellar extension and compressed optic chiasm that resulted in visual disturbance of the patients. A calcified region inside the tumor on computed tomographic scanning was also a common finding. Differential diagnosis of intrasellar salivary gland-like pleomorphic adenomas should be considered in patients with calcified intrasellar tumors with suprasellar extension. The clinical entity seems to show good prognosis if surgically removed.

Objective To determine the limiting dose to the optic apparatus in single-fraction irradiation in patients with craniopharyngioma treated with gamma knife radiosurgery (GKRS). Methods One hundred patients with 109 craniopharyngiomas treated with GKRS were evaluated with a median follow-up period of 68 months. Tumor volume varied from 0.1 to 36.0 (median, 3.3) cm. Marginal doses varied from 10 to 18 (median, 11.4) Gy. Maximum dose to any part of the optic apparatus varied from 2 to 18 (median, 10) Gy. Results The actuarial 5- and 10-year overall rates of survival of tumor progression after GKRS were 93% and 88%, respectively. Similarly, the actuarial 5- and 10-year progression-free survival rates were 62% and 52%, respectively. Among 94 patients in whom visual function was evaluable after GKRS, only 3 patients developed radiation-induced optic neuropathy, indicating an overall Kaplan-Meier radiation-induced optic neuropathy rate of 5%. Of these patients, 2 received 15 Gy or greater to the optic apparatus. Another patient who received 8 Gy or less had undergone previous fractionated radiation therapy with a biologically effective dose of 60 Gy. Conclusion The optic apparatus seems to be more tolerant of irradiation than previously thought. Careful dose planning is essential, particularly in patients who underwent prior external beam radiation therapy.

Item does not contain fulltext We present an overview of the history, development, technological advancements, current application, and future trends of cranial endoscopy. Neuroendoscopy provides a safe and effective management modality for the treatment of a variety of intracranial disorders, either tumoral or non-tumoral, congenital, developmental, and degenerative, and its knowledge, indications, and limits are fundamental for the armamentarium of the modern neurosurgeon.

OBJECTIVE: The purpose of this study was to identify biological markers that may be involved in the adhesiveness of craniopharyngiomas to optical chiasms and/or pituitary stalks. METHODS: We determined the complete pattern of integrin expression in three craniopharyngiomas by means of a complementary deoxyribonucleic acid microarray. We quantitatively determined the levels of immunohistochemical expression of the different integrins in a series of 37 cases and the pattern of immunohistochemical expression of 10 extracellular matrix components (acting as integrin ligands) in 7 optical chiasms and 11 pituitary stalks. We also quantitatively (computer-assisted microscopy) determined the levels of immunohistochemical expression of galectin-1, -3, -4, -7, and -8 in 50 adamantinomatous craniopharyngiomas. RESULTS: The present study shows that at both the ribonucleic acid and protein levels, adamantinomatous craniopharyngiomas express the alpha2, alpha6, alpha(v), beta1, beta5, and beta8 integrin subunits, whereas optical chiasms and pituitary stalks express vitronectin, thrombospondin, and various forms of collagens. CONCLUSION: Our data suggest that at least part of the adhesiveness of craniopharyngiomas to the surrounding tissue, such as optical chiasms and pituitary stalks, could be explained by the interactions between alpha(2beta1) integrin expressed by craniopharyngiomas and collagens on the one hand, and vitronectin expressed by the surrounding tissue on the other hand. In addition, a Cox regression analysis has revealed that the levels of galectin-4 contribute significant information toward the delay in recurrence independently of surgical status.

Objective To disclose the relationships of primarily supradiaphragmatic craniopharyngiomas with the third ventricular floor (3rdVF) by means of preoperative magnetic resonance imaging (MRI) and thus to select the surgical approach avoiding the hypothalamic structures. Methods MRI findings in 76 consecutive patients with craniopharyngiomas operated on between June 1991 and December 2002 were interpreted on the basis of the results of the authors' own previous microanatomic studies. The assumed tumor-3rdVF relationships were then correlated with the operative findings. MRI features characteristic for different topographical relationships were analyzed in 44 patients (18 children, 26 adults) with exclusively supradiaphragmatic tumors. Results In 14 of 15 patients with the tumor located below the 3rdVF (suprasellar extraventricular craniopharyngioma), the anterior communicating artery was displaced upward and indirectly indicated the position of the chiasm between the prechiasmatic and the retrochiasmatic tumor portions. Hydrocephalus was absent in 14 patients, including those with giant tumors. The anterior part of the third ventricular cavity was found in front of the level of the foramina of Monro in 6 patients. All 28 tumors growing partially inside and partially outside the third ventricular cavity (intraventricular and extraventricular craniopharyngioma) were retrochiasmatic. They caused severe or moderate hydrocephalus in 20 patients and mild hydrocephalus in 2. One purely intraventricular tumor caused severe hydrocephalus. Conclusion The position of the optic chiasm and the size of the lateral ventricles on preoperative MRI enable us to determine the position of the 3rdVF or its remnants in relation to the supradiaphragmatic craniopharyngiomas and to select the proper surgical approach allowing exposure of the tumor while avoiding the hypothalamic structures.

OBJECTIVE: To analyze the indications and techniques pertinent to the treatment of cranial nerve (CN) cavernous malformations (CMs). METHODS: CN CMs are lesions isolated to the CNs. CMs affecting the optic nerve (CN II), oculomotor nerve (CN III), facial/vestibulocochlear complex (CN VII and CN VIII), and hypoglossal nerve (CN XII) have been described. The records for six patients were reviewed with respect to lesion location, symptoms, surgical approach, and therapeutic considerations. This is the largest series of CMs isolated to CNs reported to date. RESULTS: Three female patients and three male patients (age range, 28-76 yr; mean age, 41 yr) presented with six CN lesions; four lesions involved the optic chiasm and two involved CN VII and CN VIII. The patients with chiasmatic lesions presented with acute visual deterioration. Both patients with CN VII/CN VIII lesions exhibited acute hearing loss. The level of deterioration suggested CM hemorrhage. Orbitozygomatic craniotomies were performed for chiasmatic lesions, and retrosigmoid craniotomies were performed for cerebellopontine angle lesions. All patients experienced symptom improvement after surgery. One chiasmatic lesion recurred after 2 years and required resection. CONCLUSION: CN CMs present with site-specific symptoms and require complex surgical techniques for resection. These lesions are frequently symptomatic, because of the eloquence of the tissue of origin. Therefore, all CN CMs should be resected. Subtotal resection uniformly results in disease and symptom recurrence. CN CMs can be resected safely, with preservation of CN function.

OBJECTIVE AND IMPORTANCE: Suprasellar meningiomas typically cause bitemporal hemianopsia by direct compression of the chiasm, its blood supply, or both. We report another mechanism for visual loss in suprasellar meningiomas, whereby compression by the suprajacent vascular complex is the offending agent. CLINICAL PRESENTATION: A 78-year-old woman with a suprasellar meningioma was diagnosed incidentally. During the follow-up period, she developed an inferior homonymous wedge defect consistent with superior compression, without any detectable radiological progression. It was decided to resect her tumor. INTERVENTION: The patient underwent a fronto-orbital approach for tumoral excision. Intraoperatively, a groove by the anterior cerebral artery complex was found along the superior surface of the chiasm. Postoperatively, the patient's visual deficit resolved. CONCLUSION: This case illustrates an unusual visual field deficit associated with a suprasellar meningioma. It also emphasizes the importance of frequent and careful visual field monitoring, which can precede radiological and symptomatic progression.

OBJECTIVE The subarachnoid space consists of a number of distinct subarachnoid cisterns. They are separated from each other by trabecular walls, one of which is Liliequist's membrane. The aim of this study was to investigate the anatomic characteristics of Liliequist's membrane. METHODS The study used a combined approach, consisting of the modified E12 sheet plastination method for 3 adult cadavers and gross anatomic dissection for 35 cadavers, 2 of which were further examined using scanning electron microscopy. RESULTS The results from this study indicate that 1) Liliequist's membrane is an avascular fold of the arachnoid mater that lacks openings and spreads out laterally, being in direct continuity with the arachnoid mater covering the tentorium; 2) the carotid-chiasmatic walls, which separate the chiasmatic cistern and carotid cisterns and had been considered to be parts of Liliequist's membrane, are vascular and incomplete trabecular walls and should not be considered parts of Liliequist's membrane; and, 3) as a fold of the arachnoid mater, Liliequist's membrane is not directly attached to the temporal lobes and oculomotor nerves. CONCLUSION Liliequist's membrane is a double-layer fold of the arachnoid mater and has anatomic characteristics different from those of arachnoid trabecular walls.

OBJECTIVE Sellar and suprasellar arachnoid cysts may be asymptomatic or may cause headache, optic nerve compression, endocrine dysfunction, or hydrocephalus. We propose a minimally invasive treatment strategy when intervention is indicated. METHODS Four patients with sellar and suprasellar arachnoid cysts presented with headache, visual compromise, and endocrine dysfunction. Two of the four patients previously had undergone unsuccessful surgical intervention. The imaging studies of two patients were diagnostic of an arachnoid cyst. RESULTS All four patients underwent stereotactic intracavitary radiation with cyst regression and symptomatic improvement. In each patient, the optic chiasm was decompressed successfully. There were no complications from the procedure. CONCLUSION Stereotactic intracavitary irradiation of arachnoid cysts proved to be safe and effective. The procedure obviated the need for open cyst fenestration or shunting.

OBJECTIVE Published morphometric data supporting the microsurgical advantages of anterior clinoidectomy are scant. The goal of this study was to quantify, with direct measurements, the improved exposure of the optic nerve, internal carotid artery (ICA), and opticocarotid triangle (OCT) after extradural removal of the anterior clinoid process. METHODS Ten formalin-fixed adult cadaver heads were dissected bilaterally, and measurements were made both before and after anterior clinoidectomy. Twenty sets of pre- and post-anterior clinoidectomy measurements were collected, consisting of: 1) optic nerve length from the optic chiasm to the optic canal (pre) and to the anulus of Zinn (post); 2) ICA length from the ICA bifurcation to the distal limit of the anterior clinoid process (pre) and to the ICA distal dural ring (post); 3) OCT width, the widest in situ distance between the optic nerve and the ICA (pre) and the analogous measurement with allowable retraction on the mobilized ICA and optic nerve (post); and 4) OCT length from the point where the A1 segment crosses the optic chiasm to the optic canal (pre) and to the anulus of Zinn (post). RESULTS The right and left combined mean values +/- standard error of the mean before and after removal of the anterior clinoid process, respectively, were: optic nerve length, 10.28 +/- 2.30 mm and 22.83 +/- 2.54 mm; ICA length, 10.48 +/- 2.39 mm and 14.78 +/- 3.02 mm; OCT width, 3.93 +/- 1.16 mm and 12.95 +/- 2.61 mm; and OCT length, 10.38 +/- 2.84 mm and 23.55 +/- 2.79 mm. CONCLUSION Anterior clinoidectomy can provide a twofold increase in exposure of the optic nerve length and the OCT length, as well as a three- to fourfold increase in the maximum OCT width. This dramatically improves surgical exposure in the suprasellar and periclinoid regions.

OBJECTIVE: The purpose of this study was to investigate the magnetic resonance features of the postoperative sella with fast spin echo (FSE) T2-weighted high-resolution imaging and to evaluate the benefits of the sequence using a follow-up magnetic resonance imaging protocol after transsphenoidal surgery. METHODS: Coronal spin echo (SE) T1-weighted and FSE T2-weighted images were prospectively obtained in 24 patients after surgery for pituitary adenomas. We observed the signals and the contour of normal structures, fluid collection, implanted materials, and mass lesions, including granulation tissue and adenoma. RESULTS: The pituitary gland was delineated in 51 of 59 FSE T2-weighted images, 90.2% of which presented clear boundaries. Whereas the gland was detected in 49 of 58 SE T1-weighted images, only 20.4% showed the boundaries. A mass lesion was identified in each of 12 patients with good resolution on FSE T2-weighted images. SE T1-weighted images detected mass lesions in 7 of 12 patients without distinctive boundaries. Contrast enhancement had little advantage in clarifying the boundaries between normal and abnormal structures. For the detection of mass lesions in the sella, the kappa values for interobserver agreement were 0.8 for FSE T2-weighted images and 0.25 for SE T1-weighted images. CONCLUSION: FSE T2-weighted imaging is a reliable method with which to assess the sella with sufficient resolution after transsphenoidal surgery. The combination of unenhanced SE T1-weighted and FSE T2-weighted images may reduce the use of contrast material after pituitary surgery.

OBJECTIVE AND IMPORTANCE: The posterior pituitary lobe is rarely the site of symptomatic primary tumors. The most common lesions arising from the neurohypophysis and the pituitary stalk seem to be granular cell tumors (GCTs), of which only 42 symptomatic cases have been reported. Here we present an unusually well-documented case of a GCT, which has implications for the differential diagnosis of sellar masses. CLINICAL PRESENTATION: A 75-year-old woman presented with decreased visual acuity, visual field loss, and a 2-year history of progressive vertigo and headaches. Neuroradiological studies showed a supra- and intrasellar, 25 x 20-mm mass, containing calcifications, that compressed the optic chiasm and extended into the third ventricle. INTERVENTION: The tumor was subtotally resected through a transsphenoidal approach. The tumor was tough and vascular and could not be suctioned. Histological examination revealed a typical GCT. The postoperative course was uneventful. Residual tumor was treated with fractionated radiation therapy. Ophthalmological testing 10 months after surgery showed a slight improvement in the visual symptoms. CONCLUSION: Tumor calcifications in computed tomographic scans do not exclude a GCT. The diagnosis requires histological confirmation. Surgical removal by the transsphenoidal approach is the therapy of choice, as for other sellar tumors. Radiation therapy may be advisable after subtotal resection. Our literature review suggests the possibility of gender-related tumor biology in GCTs.

Objective To improve the safety and efficacy of transsphenoidal pituitary adenoma surgery, we investigated transsphenoidal intraoperative color Doppler ultrasonography using a biplane transducer system. Methods We studied 23 patients with pituitary adenomas (18 patients with macroadenomas and 5 patients with microadenomas) who underwent transsphenoidal surgery. The Hitachi EUB555 color Doppler ultrasound system (Hitachi Medical, Tokyo, Japan) was used with a pediatric biplane transesophageal echo cardiography probe (EUP-ES533, 7.5 MHz, biplane phased array sector probe, 9.8-mm tip). The probe was inserted into the saline-filled sphenoid sinus after the sellar floor was opened. Intra- and suprasellar images were obtained just before dural incision and after the tumor removal was thought to have been accomplished. Results In all patients, the tumor was depicted as a slightly hyperechoic mass, as compared with the cerebrum. Using color Doppler imaging, major cerebral arteries were depicted clearly in 74% of patients. The pituitary glands, pituitary stalks, and optic chiasms were observed in patients with small adenomas, but not when large adenomas were present. Cavernous sinus invasion, concomitant aneurysm, and residual tumor were clearly visualized. In patients with large adenomas, the end point of surgery was decided when there was an ultrasonographically demonstrated collapsed tumor capsule, subcapsular total vacancy, and reappearance of the optic chiasm. Conclusion Trans-sellar color Doppler ultrasonography seems to be a useful intraoperative guiding system that may improve the safety and efficacy of transsphenoidal surgery.

Objective Magnetic resonance imaging and computed tomography provide good anatomic detail of suprasellar tumors in pediatric patients but are not able to predict histology in many cases. Proton magnetic resonance spectroscopy provides metabolic data that may add to diagnostic specificity. We preoperatively performed localized proton magnetic resonance spectroscopy on pediatric patients with suprasellar tumors and correlated the results with the histological findings. Cyst fluid obtained from patients with craniopharyngiomas was studied with high-resolution magnetic resonance spectroscopy to better understand the in vivo data. Methods Nineteen patients aged 1 to 21 years underwent spectroscopy. Surgical pathological samples were obtained from 14 patients. In each of five patients, the presence of a solid chiasmatic mass in addition to clinical evidence of neurofibromatosis Type I allowed the presumptive diagnosis of chiasmatic astrocytoma. Thus, the study population included 6 patients with craniopharyngiomas, 10 with chiasmatic/hypothalamic astrocytomas, and 3 with pituitary adenomas. The data obtained were compared with those of healthy brain from age-matched participants. Results Spectroscopy was specific for the diagnosis. All craniopharyngiomas showed a dominant peak at 1 to 2 ppm, consistent with lactate or lipids, with trace amounts of other metabolites. This was confirmed using high-resolution spectroscopy. Chiasmatic gliomas showed a profile of choline, N-acetylaspartate, and creatine, and the choline:N-acetylaspartate ratio was 2.6 +/- 1.3, compared with 0.7 +/- 0.3 for samples of healthy brain (t test, P = 0.0003). Pituitary adenomas showed only a choline peak or no metabolites at all. Conclusion Proton spectroscopy may be helpful in supplementing standard imaging for the preoperative diagnosis of three types of suprasellar tumors that are common in pediatric patients.

Background Suprasellar meningiomas often invade the optic canals (OCs). The feasibility of removing these tumors through a minimal-access endonasal route has been demonstrated, but the importance, safety, and timing of OC exploration and decompression are not well described. Objective To create a simple decision-tree algorithm for OC exploration and decompression in the endonasal endoscopic surgery for planum sphenoidale and tuberculum sella meningiomas. Methods We identified a consecutive series of 8 planum sphenoidale and tuberculum sella meningiomas resected endonasally. "Late" OC exploration and decompression was performed in 4 of 8 patients. The extent of resection, visual outcome, and complications were recorded. Results Five patients had OC invasion on magnetic resonance imaging. Endoscopic inspection did not reveal additional OC invasion. The OC was opened bilaterally in 2 patients and unilaterally in 2 patients. Gross total resection was achieved in 6 of 7 patients in whom it was the goal. Vision improved in 3 patients (3 of 3 OCs opened) and was stable in 4 (1 of 4 OCs opened). In 1 patient, the bitemporal hemianopsia improved, but there was unilateral deterioration (no OC invasion) because the tumor was extremely adherent to 1 optic nerve. After an average follow-up of 20.9 months, all patients had an Glasgow Outcome Scale score of 5, and there were no cerebrospinal fluid leaks. Conclusion Exploration and decompression of the OC are feasible, safe, and important to optimize visual outcome and to minimize recurrence in planum sphenoidale and tuberculum sella meningiomas resected endonasally. It may not be important to open the canal early during surgery because tumor debulking can be performed without manipulating the optic nerves. Early decompression, however, is technically feasible.

Two men undergoing transsphenoidal exploration for pituitary adenoma were found to have lymphocytic hypophysitis. Both presented with frontal headaches, lethargy, and diminished libido. Laboratory investigations showed markedly depressed serum testosterone, and magnetic resonance imaging demonstrated pituitary enlargement, with optic chiasm involvement. Intraoperatively, the dura was adherent to the pituitary in each case. The resected glands were effaced by a dense lymphoplasmacytic infiltrate and fibrosis, without granulomas. Nonspecific peripheral enhancement on imaging suggested a diagnosis other than adenoma, but more experience with peripheral enhancement in lymphocytic hypophysitis is needed. The diagnosis was histological and required surgical intervention. Long-term pituitary replacement therapy is usually required.

BACKGROUND: Several minimally invasive modifications of the standard pterional approach have been proposed recently. The lateral supraorbital approach is one of these modifications. OBJECTIVE: To provide a qualitative and quantitative anatomic comparison of the surgical exposure and the operability afforded by the standard pterional approach and the lateral supraorbital approach. METHODS: Eight pterional approaches and 8 lateral supraorbital approaches were used in 8 fresh human cadaver heads. One qualitative and 2 quantitative tools were used to assess the surgical exposure. RESULTS: Qualitatively, the lateral supraorbital approach has the advantages of reduced trauma to the temporalis muscle and exposure that is comparable to that provided by the standard pterional approach to the sellar and suprasellar regions. This approach offers limited exposure of the interpeduncular fossa compared with the pterional one. Quantitatively, the pterional approach provides a greater surgical volume than the lateral supraorbital approach (32.90 mL vs 23.60 mL with P < .05). Also, the pterional approach provides a greater associated surgical operability than the lateral supraorbital approach (exposure score of 66 and 53, respectively). However, the lateral supraorbital approach offers an equivalent access to the anterior communicating artery complex, optic nerve, optic chiasm, and sellar area (the exposure scores were 19 for both approaches). CONCLUSION: From an anatomic point of view, both approaches provide similar exposure to the sellar, suprasellar, and anterior communicating artery areas. The pterional approach provides better exposure of the retrosellar area. The ability to operate in the retrosellar area, as judged by our model, was higher with the pterional than with the lateral supraorbital approach.

Low-grade astrocytomas of the midline of the brain can be difficult to manage because of their location. To evaluate treatment and outcome, we performed a retrospective study of children with midline low-grade astrocytomas admitted to The Hospital for Sick Children between 1976 and 1991. Eighty-eight children with biopsy-proven low-grade astrocytomas were identified. Forty-three tumors occurred in the optic pathways or hypothalamus, 13 in the thalamus, 7 in the pineal region, 14 in the midbrain, and 11 in the medulla. Patient follow-up ranged from 6 months to 15 years, with a mean of 4 years, 9 months. Overall outcome was related to the extent of resection, histological type, and location. Partial resections were often associated with involution of the tumor. Response to radiation was variable, and serious sequelae were observed. Thirty-three patients experienced recurrence, often with a good response to subsequent surgery; however, 12 of these patients died. The probability of survival was calculated to be 96% at 1 year, 91% at 5, and 80% at 10 years. Our study suggests that resection should be considered in all patients, both at presentation and recurrence.

Background and importance Langerhans cell histiocytosis (LCH) is an uncommon disease, usually affecting the cranium and peripheral bones. We present a rare case of isolated optic chiasm involvement by LCH to highlight the importance of considering LCH in the differential diagnosis of optic chiasm lesions. Clinical presentation A 71-year-old woman presented with a 6-week history of worsening peripheral vision, headaches, weakness, cold sensitivity, and fatigue. She was found to have dense bitemporal hemianopsia. Magnetic resonance imaging revealed a 2-cm lesion, contrast enhancing on T1 and bright on T2 signal, involving the optic chiasm but not the pituitary gland. Preoperative considerations included optic nerve glioma, choristoma of the stalk, sarcoid, hypothalamic glioma, and Langerhans cell histiocytosis. The patient underwent a right subfrontal craniotomy for biopsy of the lesion. The optic chiasm was grossly enlarged with no tissue external to the chiasm. A midline incision was made in the lamina terminalis, and multiple biopsies were taken of firm fibrous material. Histologically, the tumor was characteristic for LCH and included a mixture of histiocytes with features of Langerhans cells, eosinophils, small lymphocytes, macrophages, neutrophils, and plasma cells. Conclusion LCH is a rare disease, generally affecting bone, skin, lymph nodes, and in more severe cases, visceral organs. LCH involving the optic pathways is a rare condition that should be included in the differential for adults with mass lesions involving the orbit, eye, optic nerve, or chiasm. Future clinical and basic science research is needed to better understand LCH, its molecular origin, and its growth pattern.

Lymphocytic hypophysitis (adenohypophysitis) is a rare lymphocytic infiltration of the pituitary gland that usually occurs during pregnancy. Because of its rarity, it has seldom been diagnosed preoperatively, and no trials of therapeutic treatment have been reported to date. We describe a 29-year-old woman with a pituitary mass and visual-field defects during pregnancy. The patient's pituitary profile revealed an abnormal thyroid axis and relatively low prolactin for her stage of pregnancy. This finding suggested adenohypophysitis, and the patient was given a trial course of dexamethasone. The progression of the visual-field defects, however, indicated that the steroids, both in dosage and duration, were not effective. Thus, the patient underwent a partial hypophysectomy for decompression. The pathology report confirmed adenohypophysitis, and steroids were continued for the remainder of the pregnancy, with slow resolution of the visual-field defects to normal. This report is the first case of adenohypophysitis where the diagnosis was suspected preoperatively, and a trial course of steroids was given. The steroids at the dosage and duration used were not effective. Further evaluation of the use of steroids in this disease is warranted.

OBJECTIVE Radiation therapy is recommended for pituitary tumors that are refractory to surgical and medical therapies. The efficacy of single-fraction radiosurgery is established for these lesions, but lesions within 3 mm of the optic pathway cannot be safely treated with doses higher than 8 to 10 Gy. We hypothesized that the optic nerve will tolerate 5 consecutive daily radiosurgery fractions of 500 cGy with effective tumor control. METHODS We reviewed our first 20 patients with recurrent or residual pituitary adenomas within 3 mm of the optic chiasm treated with the CyberKnife radiosurgery system (Accuray, Inc., Sunnyvale, CA). Tumors were treated with a mean coverage of 97 +/- 2.2% (range, 89.8-99.7%), a mean conformity index of 1.3 +/- 0.2 (range, 1.1-1.6), and a mean treatment isodose line of 74.5 +/- 6.6% (range, 60-86%). The primary end point was an interim analysis of visual preservation, and secondary end points were radiographic and endocrinological tumor control. RESULTS The mean follow-up period for visual field testing was 26.6 +/- 10.5 months (range, 10.6-41 months). The vision of all 14 patients with intact preoperative vision remained intact. Of the 5 patients with impaired vision, 2 remained stable, and 3 improved. No patient's vision deteriorated. The mean radiographic follow-up was 29.3 +/- 8.6 months (range, 10.2-40.5 months). On magnetic resonance imaging, 12 tumors were stable, 8 were smaller, and none enlarged. CONCLUSION This preliminary study establishes that the optic nerve and chiasm tolerate CyberKnife hypofractionated radiosurgery of 5 x 500 cGy to perichiasmatic pituitary adenomas. Early data suggest that this dosing paradigm may achieve satisfactory radiographic and endocrinological tumor control for these challenging lesions, but longer follow-up is necessary to confirm these results.

A 26-year-old woman was treated for a prolactin secreting pituitary adenoma by surgery and radiotherapy (5860 rads). Fourteen months later, she developed right hemiparesis and dysarthria. A T1-weighted magnetic resonance imaging scan using gadolinium contrast showed a small, enhanced lesion in the upper pons. Seven months later, she had a sudden onset of loss of vision, and radiation optic neuropathy was diagnosed. A T1-weighted magnetic resonance imaging scan showed widespread gadolinium-enhanced lesions in the optic chiasm, optic tract, and hypothalamus. Magnetic resonance imaging is indispensable for the early diagnosis of radiation necrosis, which is not visualized by radiography or computed tomography.

Angiographically occult vascular malformations of the optic nerve and chiasm are extremely rare. Before the advent of magnetic resonance imaging (MRI), it was difficult to diagnose these lesions preoperatively. We report MRI scan findings of optic chiasm cavernous angiomas in two patients with chiasmal syndrome. MRI was useful in localizing the vascular malformation and delineating its characteristics, especially chronic hemorrhage. One patient underwent biopsy of the lesion. The other patient underwent complete microsurgical resection of the malformation with the carbon dioxide laser with preservation of vision. Occult vascular malformations of the optic nerve and chiasm may be a more common cause of visual deterioration than previously recognized. The MRI scan is the imaging modality of choice for diagnosing and following these lesions. In certain patients, these vascular malformations may be amenable to complete surgical removal with stabilization or improvement of visual function.

We describe a case of ganglioglioma of the optic chiasm and tract in a 33-year-old man. Review of the literature discloses only seven cases of tumors of the anterior visual pathway that meet the histological criteria for such neoplasms. A detailed histological description of our case and a review of the literature is provided.

OBJECTIVE: To assess the extent to which the transsphenoidal speculum can be safely opened at the face of and within the sphenoid sinus without risking damage to the optic nerves in the optic canals and at the orbital apex and the nerves coursing adjacent the walls of the sphenoid sinus. METHODS: The distance was measured between the optic nerves at the level of the anterior wall of the sphenoid sinus and 0.5 and 1.0 cm within the sinus. In addition, the distance between the middle turbinates and the contralateral optic canals was assessed because this turbinate is the largest structure blocking access to the sphenoid sinus in the transsphenoidal approach and tends to force the speculum away from the midline and toward the optic nerve in the contralateral side of the approach. RESULTS: Opening the transsphenoidal speculum at the anterior wall of the sphenoid sinus beyond 2.5 centimeters carries some risk of damaging the optic nerves and this distance narrows when the speculum opening is positioned inside the sphenoid sinus. Displacement of the speculum to one side by the middle turbinate places the speculum near the contralateral optic nerve and may be associated with optic nerve injury with lesser degrees of speculum opening. CONCLUSIONS: Careful attention should be directed to avoiding excessive opening of the transsphenoidal speculum at the anterior face of the sphenoid or within the sphenoid sinus.

OBJECTIVE: We present a quantitative comparison of radiosurgery treatments for cavernous sinus tumors using the Leksell gamma knife Model U versus the Model C with automatic positioning system (APS) (Elekta instruments, Norcross, GA). METHODS: At our medical center from August 1994 through May 2000, the Model U was used to treat 96 patients (37 men [39%] and 59 women [61%]; median age, 54.5 yr) with benign cavernous sinus turners: 43 meningiomas (45%), 48 pituitary tumors (50%), and 5 others (5%). From June 2000 through April 2002, the Model Ct with APS treated 45 patients (20 men [44%] and 25 women [56%]; median age, 51.4 yr) with 15 meningiomas (33%), 29 pituitary tumors (65%), and 1 schwannoma (2%). The two groups had similar treater tumor volumes (Model U mean, 4.3 cm 3 ; Model C mean, 4.2 cm 3 ), equivalent tumor distance prom critical structures (optic nerve, chiasm, and pons), comparable distributions in Sekhar tumor grades, and the same median prescribed dose of 15 Gy to the 50% isodose line at the tumor periphery. All planning and treatments were performed by the same radiosurgery team to minimize dosage to adjacent critical tissues and to optimize conformity index. RESULTS: Analysis of multiple treatment parameters showed that the Model C plans were superior. Model C treatments had an improved conformity index (Model U mean, 1.7; Model C mean, 1.6; P < 0.02) and a lower underdosed tumor volume (Model U mean, 0.4 cm 3 ; Model C mean, 0.1 cm 3 ; P < 0.004). The total treated volume and the excess treated volume were similar. The Model C group had a reduction in optic chiasm dose (Model C mean dose, 3.8 Gy; Model U mean dose, 5.3 Gy; P

OBJECTIVE: The limited radiation tolerance of the optic nerves and the optic chiasm makes it a challenge to treat immediately adjacent lesions with radiosurgery. Staged or hypofractionaled radiosurgery has the virtue of combining the accuracy and conformality of radiosurgery with the normal tissue sparing benefits of fractionation. We describe a consecurtive series of patients with meningiomas and pituitary adenomas abutting the anterior visual pathways who were treated with staged, image-guided radiosurgery. METHODS. Thirty-four patients with either meningiomas (20 patients) or pituitary adenoma (14 patients) within 2 mm of the optic apparatus were treated. Several patients had previously been treated with conventional fractionated radiotherapy (5 patients) or subtotal surgical resection (23 patients). Radiosurgery was delivered in two to five stages to a cumulative average marginal dose of 20.2 Gy. Visual testing and clinical examinations were performed before treatment and at follow-up intervals beginning at 6 months after treatment. RESULTS: The mean follow-up period was 29 months (range, 15-62 mo). Pre- and posttreatment vision was unchanged in 20 patients, improved in 10, and worser in 3. One patient died during follow-up as a result of an unrelated cardiac event. Visual loss was accompanied by tumor progression in two cases. In a third patient with a multiply recurrent adrenocorticotropic hormone-secreting pituitary adenoma, injury to one otpic nerve occurred after both a prior course of radiotherapy and three separate sessions of radiosurgery. CONCLUSION: Staged radiosurgery resulted in high rates of tumor control and preservation of visul function. Ninety-one percent of patient retained their presurgical vision. Staged radiosurgery may be a safe and effective alternative to either surgery or fractionated radiotherapy for selected lesions adjacent to the optica apparatus.

Objective and importance Although it is well known that large or giant internal carotid artery-ophthalmic artery aneurysms can cause visual deficits, penetration and schism of the optic nerve by an aneurysm are very rare. Clinical presentation A 48-year-old man presented with an acute onset of right visual deterioration after an episode of severe headache. Magnetic resonance imaging demonstrated penetration of the right optic nerve by an intracranial aneurysm. Cerebral angiography revealed an internal carotid artery-ophthalmic artery aneurysm of 12 x 7 mm. The aneurysm was directed superomedially and appeared to have a "waist" within the penetration. Intervention Intraoperatively, we observed that part of the aneurysm wall was visible through the optic nerve fibers at the junction with the optic chiasm. Conclusion Although there was no direct evidence of subarachnoid hemorrhage on imaging scans or with operative exploration, we think that the patient must have experienced sentinel hemorrhaging, leading to visual deterioration. We describe the case in detail and review the world literature.

OBJECTIVE We report a case in which fractionated gamma knife radiosurgery was used to treat a metastatic melanoma lesion. The tumor demonstrated a rapid response to radiosurgery with an observable reduction in tumor volume between the second and third treatments, requiring a favorable modification in the third fractionated treatment. CLINICAL PRESENTATION A 61-year-old woman presented with a frontal floor metastatic melanoma lesion that was located adjacent to the optic apparatus. INTERVENTION Gamma knife radiosurgery was administered in three fractionated treatments of 6.5 Gy to the 50% isodose line in each case. Repeat imaging for the purpose of planning demonstrated that tumor volume at the time of the third treatment, 9 days following the first treatment, had decreased by 31%, resulting in a 21% decrease in the dose administered to the optic chiasm. CONCLUSION A case of metastatic melanoma treated with fractionated GKRS is presented, in which a significant reduction in tumor volume was noted 9 days following the initial treatment. This case provides insight into the rate with which malignant neoplasms may respond to intermediate-dose hypofractionated GKRS, and lends support to the concept of "adaptive radiosurgery" as a means of optimizing radiation to an evolving target while minimizing collateral radiation to surrounding structures.

OBJECTIVE This study was undertaken to define more accurately the feasibility and indications of the contralateral pterional approach to ophthalmic segment aneurysms of the internal carotid artery (ICA). METHODS Between 1995 and 1999, 46 patients with ophthalmic segment aneurysms of the ICA were surgically treated in our institution. Eleven of the 46 aneurysms were operated using the contralateral pterional approach. All aneurysms were successfully clipped without complications; three patients required bone resection around the aneurysm neck. We studied the 11 patients who were treated with the contralateral approach by defining six parameters to assess the feasibility of the approach and to predict the necessity for bone resection: 1) Parameter A, the distance between the anterior aspect of the optic chiasm and the limbus sphenoidale; 2) Parameter B, the distance between the bilateral optic nerves at the entrance to the optic canal; 3) Parameter C, the interrelation of the optic nerve and the ICA, expressed as a/b in which a is the length from the midline to the optic nerve and b is the length from the midline to the ICA; 4) Parameter D, the size of the aneurysm neck; 5) Parameter E, the direction of the aneurysm from the ICA wall on the anteroposterior angiogram; and 6) Parameter F, the distance from the medial side of the estimated distal dural ring to the proximal aneurysm neck on the lateral angiogram. RESULTS Parameters A to F were 8.8 mm (range, 5.4–11.1 mm), 14.5 mm (range, 10.4–22.2 mm), 0.9 mm (range, 0.6–1.3 mm), and 3.0 mm (range, 2.3–4.7 mm), 5 to 160 degrees, and 1.3 mm (range, 0.3–2.4 mm), respectively. All patients had excellent operative outcomes without visual dysfunction. Three patients required drilling of the bone around the optic canal on the craniotomy side; bone drilling was not required when Parameter E was between 30 and 160 degrees and Parameter F was more than 1 mm. CONCLUSION Parameters A to D are important for assessing the feasibility of the contralateral approach to ICA-ophthalmic segment aneurysms, and Parameters E and F are most useful for calculating the difficulty of this approach.

OBJECTIVE: Rosette-forming glioneuronal tumor is a rare, rather recently described tumor featuring a highly distinctive, biphasic histological pattern, including a cytologically uniform neuronal component of Homer-Wright type pseudorosettes and an accompanying astrocytic element resembling pilocytic astrocytoma. Its occurrence in the posterior fossa and association with the fourth ventricle is stereotypical and a feature of all reported cases. CLINICAL PRESENTATION: In this article, we describe the first rosette-forming glioneuronal tumor arising outside this site, a histologically classic example involving the anterior visual pathway and associated with neurofibromatosis type 1. INTERVENTION: Genetic (fluorescent in situ hybridization) studies demonstrated no large deletion in either normal or neoplastic tissue, indicating that the genetic abnormality underlying neurofibromatosis type 1 in this patient is likely a very small deletion or point mutation. CONCLUSION: The relation of the tumor to the underlying neurofibromatosis type 1 cannot be assessed.

OBJECTIVE Hydrogel-coated coils (MicroVention, Inc., Aliso Viejo, CA) for endovascular aneurysm treatment offer the theoretical advantages of increased volumetric occlusion, thrombus stabilization, and improved neointimal healing. Reports of local inflammation and hydrocephalus after coiling of unruptured aneurysms have raised questions about the safety profile or appropriate usage of these new devices. CLINICAL PRESENTATION Two patients with large ophthalmic aneurysms underwent elective endovascular coiling with HydroCoils. Three to 4 weeks later, they developed profound, progressive bilateral visual loss. Magnetic resonance imaging scans demonstrated extensive enhancement of the coil ball, surrounding brain parenchyma, and optic chiasm, with perianeurysmal edema. INTERVENTION Dexamethasone produced impressive but temporary improvement in vision in one patient; the other experienced only minor improvement. One patient also developed hydrocephalus; ventriculoperitoneal shunting reduced ventricular size but had no effect on vision. Follow-up imaging demonstrated persistent enhancement of the coil ball, as well as recurrence and extension of the abnormal signal in the parenchyma and along the optic tract. CONCLUSION Both patients have been left with no functional vision in the eye ipsilateral to the aneurysm and have experienced marked visual field loss and reduced acuity in the contralateral eye. Ongoing international studies will provide more information on the rate of inflammatory complications. The biological mechanisms underlying the phenomenon also require investigation. Meanwhile, we caution against using HydroCoils in situations in which worsened mass effect or local inflammation would have highly deleterious consequences, such as in large aneurysms adjacent to the visual pathways or the brainstem.

Objective The vicinity of carotid-ophthalmic aneurysms to the roof of the cavernous sinus, to the anterior clinoid process, and to the optic nerve or the optic chiasm requires well-defined surgical techniques. Although microsurgical techniques with ipsilateral direct approaches to these aneurysms have been described in detail, studies about contralateral strategies for the microsurgical treatment of carotid-ophthalmic aneurysms are rare and are mainly confined to case reports. The aim of this study is to describe how to decide on the ipsilateral and contralateral microsurgical approaches to such aneurysms and to demonstrate the surgical techniques for the ipsilateral and contralateral exposure of carotid-ophthalmic aneurysms. Methods In a series of 51 patients with 58 aneurysms of the ophthalmic segment of the internal carotid artery, nine patients with 10 aneurysms (4 large aneurysms, 6 small aneurysms) were treated via a contralateral microsurgical approach after careful preoperative planning. Preoperative planning was based on the analysis of clinical and radiographic data, including cranial computed tomography, magnetic resonance imaging, magnetic resonance angiography, and conventional cerebral angiography. Results The postoperative results were good in 38 (75%) of the patients, fair in 2 (4%), and poor in 3 (6%); 8 (15%) of the patients died after surgery. The postoperative follow-up was 4 months to 10 years. Postoperatively, 15 of 19 patients with uni- or bilateral visual deficits or visual field defects improved, 3 of the 19 patients experienced postoperative impairment of visual function, and 1 of the 19 patients had an unchanged visual field deficit. Visual impairment or unchanged visual function was observed in patients who underwent ipsilateral approaches, which was possibly caused by inappropriate intraoperative retraction of the optic nerve or chiasm. In all patients presenting with preoperative visual deficits who were treated via contralateral approaches, visual function improved in the postoperative course. Conclusion Giant carotid-ophthalmic aneurysms that are eligible for surgical treatment as well as small and large aneurysms dislocating the optic nerve or the chiasm superomedially or medially should be approached via ipsilateral craniotomies. It is recommended that small and large aneurysms of the carotid-ophthalmic segment originating medially, superomedially, or superiorly, displacing the optic nerve or the chiasm superiorly, superolaterally, or laterally, be approached via contralateral craniotomies.

The anatomy of Liliequist's membrane was studied in seven adult human cadavers by a technique that preserves the cisternal shape, stains arachnoid membranes violet, and fills the arteries with red gelatin. Our findings suggest the following about Liliequist's membrane: it is located between the interpeduncular cistern posteriorly, the carotid cisterns anterolaterally, and the chiasmatic cistern anteromedially; it is attached laterally to the mesial surface of the temporal lobe above the tentorial edge; it lies posterior to the infundibulum; and it presents a free edge between the optic tract and the temporal uncus.

Malformations of the diaphragma sellae may permit transdiaphragmatic cerebrospinal fluid pulsations that lead to expansion of the sella turcica. The purpose of this report is to describe an intrasellar arachnoid cyst observed during surgery being filled by the action of an apparent one-way valve.

Angiographically occult vascular malformations of the optic nerve and chiasm are extremely rare. Before the advent of magnetic resonance imaging (MRI), it was difficult to diagnose these lesions preoperatively. We report MRI scan findings of optic chiasm cavernous angiomas in two patients with chiasmal syndrome. MRI was useful in localizing the vascular malformation and delineating its characteristics, especially chronic hemorrhage. One patient underwent biopsy of the lesion. The other patient underwent complete microsurgical resection of the malformation with the carbon dioxide laser with preservation of vision. Occult vascular malformations of the optic nerve and chiasm may be a more common cause of visual deterioration than previously recognized. The MRI scan is the imaging modality of choice for diagnosing and following these lesions. In certain patients, these vascular malformations may be amenable to complete surgical removal with stabilization or improvement of visual function.

Eleven patients who experienced significant loss of vision after transsphenoidal surgery are reported on. The mechanisms involved in these visual complications include direct injury or devascularization of the optic apparatus, fracture of the orbit, postoperative hematoma, cerebral vasospasm, and prolapse of the optic chiasm into an empty sella. Factors that may increase the risk of visual complications include the presence of a pituitary macroadenoma, previous visual impairment, a “bottleneck” or dumbbell-shaped tumor, previous surgery and/or radiation therapy, and, possibly, use of a lumbar subarachnoid catheter during operation. A practical approach to the management and avoidance of these complications is presented.

We describe a case of ganglioglioma of the optic chiasm and tract in a 33-year-old man. Review of the literature discloses only seven cases of tumors of the anterior visual pathway that meet the histological criteria for such neoplasms. A detailed histological description of our case and a review of the literature is provided.

OBJECTIVE AND IMPORTANCE Chiasmal apoplexy, defined as hemorrhage into the optic chiasm, generally is caused by an intrachiasmal vascular malformation. We report the first case of chiasmal apoplexy due to hemorrhage from a pituitary macroadenoma into the optic chiasm. CLINICAL PRESENTATION A 52-year-old man presented with headache, sudden and severe deterioration of visual acuity in the left eye, and a bitemporal visual field deficit. Magnetic resonance imaging revealed a large intra- and suprasellar homogeneously enhancing mass, which elevated a markedly thickened optic chiasm. After emergent transsphenoidal resection of the pituitary adenoma, vision did not improve. INTERVENTION A pterional craniotomy was subsequently performed, during which a hematoma was found and evacuated from within the substance of the left optic nerve and chiasm. The hematoma cavity was found to communicate with the sella through a defect in the diaphragm. Vision improved dramatically after the operation. CONCLUSION Chiasmal apoplexy resulting from pituitary adenoma should be distinguished from pituitary apoplexy, particularly because it requires a different surgical treatment. Clinical and radiographic features that may help distinguish the two are discussed.

Interest in the anatomy of the proximal segment of the intracranial internal carotid artery has been kindled by the recognition that there are multiple potential sites of aneurysm formation in this region. These various aneurysm locations have characteristic hemodynamic and clinical features as well as surgical considerations. Recently recognized as a distinct clinical and anatomical entity are aneurysms that are hemodynamically related to the superior hypophyseal artery. Although aneurysms arising in proximity to the superior hypophyseal artery are not rare, the anatomy of this vessel arising from the medial or posteromedial aspect of the proximal internal carotid artery is poorly understood. We performed a cadaveric microsurgical anatomical study of 20 internal carotid arteries between the ophthalmic and posterior communicating arteries to develop a better understanding of the anatomical relationships of the superior hypophyseal artery. There were an average of 1.8 superior hypophyseal arteries arising from each carotid artery with an average diameter of 0.22 mm. The origin of the superior hypophyseal arteries was within 5 mm of the ophthalmic artery origin in 85% of the specimens. There were two distinct patterns of superior hypophyseal artery anatomy. In 42%, a large, dominant superior hypophyseal artery branched like a candelabra with smaller branches to the pituitary stalk, optic nerve, and chiasm. The average diameter of the larger branches was 0.3 mm. In the absence of a large dominant branch, two or three medial vessels were found. In one specimen, an incidental aneurysm was discovered at the origin of the superior hypophyseal artery on the medial aspect of the internal carotid artery at the origin of a large candelabra-like branch.(ABSTRACT TRUNCATED AT 250 WORDS)

A pilocytic astrocytoma of the optic nerve, chiasm, hypothalamus, or third ventricle is a relatively common tumor of childhood. This case report illustrates such a tumor, originating from this location, which is unusual because of the association with two very large cystic extensions into the middle cranial fossa and into the third ventricle. The massive size and extent of this tumor and cysts was demonstrated on a magnetic resonance imaging (MRI) scan, with gadolinium enhancement. This case illustrates a novel macroscopic appearance for a pilocytic glioma of the anterior third ventricle. The purpose of this report is to alert clinicians to the varied morphology this tumor may present as we apply increasingly our improved radiological, operative, and histopathological techniques. (Neurosurgery 26:133-137, 1990)