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Objective: Although endoscopic perforation of the septum pellucidum in obstruction of the foramen of Monro is well known, detailed reports on endoscopic septostomy, including surgical technique and results are lacking in the literature., Methods: All intracranial endoscopic procedures performed between February 1993 and March 2008 were evaluated. All patients with blockage of the foramen of Monro that was treated with endoscopic septostomy were analyzed and prospectively followed. Particular attention was given to indications, approach, surgical technique, complications, and results., Results: Thirty-two endoscopic septostomies were performed in 30 patients (17 male patients, 13 female patients; mean age, 31 years; age range, 4 months-68 years). Cerebrospinal fluid circulation was obstructed by tumor (16 cases), multiloculated cystic hydrocephalus (8 cases, including 2 revisions), septum pellucidum cysts (3 cases), membranous or inflammatory isolated lateral ventricles (3 cases), and giant aneurysms (2 cases). Simultaneously with septostomy, 13 endoscopic tumor procedures, 9 endoscopic third ventriculostomies, and 9 other endoscopic procedures were performed. The mean surgical time was 80 minutes (range, 45-135 minutes). There were 4 asymptomatic complications (13%), 5 transient complications (16%), and no permanent complications. Postoperatively, 26 patients (87%) improved. Two revisions had to be performed. The mean follow-up period was 16 months (range, 1-93 months)., Conclusion: On the basis of the results, long-standing cerebrospinal fluid circulation restoration can be achieved with endoscopic septostomy. Endoscopic septostomy is a safe and reliable endoscopic technique that should be considered more frequently for the restoration of cerebrospinal fluid circulation in the treatment of blockage of the foramen of Monro.

Objective: Dysembryoplastic neuroepithelial tumor (DNT)-like neoplasms of the septum pellucidum are extremely rare. In this article, we report the familial occurrence of these neoplasms., Clinical Presentation: We report two cases of such neoplasms: Patient 1, a 42-year-old woman, and Patient 2, the 20-year-old nephew of Patient 1. Patient 1 experienced headache and worsening dizziness; Patient 2 experienced headache and worsening dizziness and also had partial seizures. In both cases, magnetic resonance imaging (MRI) revealed an intraventricular tumor adjacent to the septum pellucidum. Both tumors appeared as a hypointense region on T1-weighted MRI, and both appeared as a hyperintense region on T2-weighted MRI without gadolinium enhancement. Interestingly, both tumors had a high apparent diffusion coefficient., Intervention: Both tumors were subtotally removed and had common histological findings, such as alveolar structures with oligodendroglia-like cells and "specific glioneuronal element." These findings are consistent with a dysembryoplastic neuroepithelial tumor-like neoplasm. After tumor removal, the symptoms disappeared. The postoperative course was uneventful, and the patients did not require adjuvant therapy. MRI showed no regrowth of residual tumors at 4 years (Patient 1) and 2 years (Patient 2) postoperatively., Conclusion: The familial occurrence of this rare tumor suggests that both of these cases arose from a common germline mutation. Identification of this rare tumor in this rare location is important to avoid unnecessary adjuvant therapy. A markedly high apparent diffusion coefficient and histological findings of specific glioneuronal element can facilitate the differential diagnosis of dysembryoplastic neuroepithelial tumor-like neoplasms. Genetic study of affected patients in this family may provide clues to its molecular pathogenesis.

Objective: Cysts of the septum pellucidum (CSPs) may become symptomatic because of obstruction of cerebrospinal fluid flow, resulting in increased intracranial pressure and hydrocephalus requiring surgical intervention. Endoscopic fenestration may be the most effective and least invasive technique to treat this pathological condition., Clinical Presentation: An 11-year-old boy sought treatment for frequent episodes of severe headache. On examination, he had papilledema. There was evidence on magnetic resonance imaging scans of a space-occupying CSP with obstructive hydrocephalus., Intervention: The endoscopic technique of fenestration of both lateral walls of an enlarged CSP via a left frontal approach under ultrasound guidance using a rigid endoscope was successful. After surgery, the patient became asymptomatic, his papilledema resolved, and magnetic resonance imaging scans demonstrated collapse of the walls of the CSP toward the midline., Conclusion: Neuroendoscopic fenestration should be strongly considered as the treatment of choice for symptomatic CSPs. This procedure alone can lead to complete resolution of clinical symptoms and hydrocephalus, can reduce the size of the CSP, and can obviate the need for an implantable cerebrospinal fluid shunt.

Objective: Ten rare cases of symptomatic septum pellucidum cysts in patients who underwent endoscopic fenestration are described. The approaches and techniques used in the management of these cysts and the endoscopic surgical indications are discussed., Clinical Presentation: In the past 5 years, 10 patients (age range, 3-60 yr) with symptomatic septum pellucidum cysts underwent neuroendoscopic fenestration. The most common symptom was intermittent headache (seven patients) accompanied by dizziness, vomiting, and epileptic seizures. Two patients presented with epileptic seizures. One patient presented with abnormally increased head circumference. Magnetic resonance imaging scans of 10 patients showed septum pellucidum cysts, two with hydrocephalus, and two with pituitary microadenoma., Intervention: All 10 patients underwent endoscopic fenestration with a rigid endoscope via a frontal approach. Eight cases were performed freehand. Two cases were assisted by a frameless neuronavigation system. Postoperatively, the mass effect of the cysts and the symptoms resolved immediately, and computed tomographic or magnetic resonance imaging scans showed significant decrease in the cyst size and no recurrence during follow-up. Ventricular sizes in the two patients with hydrocephalus were normal., Conclusion: Neuroendoscopic pellucidotomy could be an effective, safe, and convenient therapeutic method for symptomatic septum pellucidum cysts. This approach might provide communication between the cyst and the ventricular system, thus avoiding shunting or craniotomy. We consider that it is appropriate to use the rigid endoscope via the frontal approach. It is helpful to fill the ventricles with lactated Ringer's solution and leave an external drain after surgery.

Objective and Importance: We describe two patients with symptomatic septum pellucidum cysts managed by endoscopic fenestration. In each case, tissue from the cyst wall was studied to define the origin of the cyst wall and fluid., Clinical Presentation: The patients, a 6-year-old boy and a 42-year-old man, each presented with headaches and a syncopal episode. Imaging studies demonstrated large septum pellucidum cysts with obstruction of the foramina of Monro., Intervention: The patients underwent endoscopic transventricular cyst fenestration with a 4-mm steerable fiberscope. The fenestrations were created to allow communication with the right and left lateral ventricles. In one patient, adhesions between the cyst wall and the foramen of Monro were lysed with endoscopic monopolar cautery. Tissue from the cyst walls was removed for examination by electron microscopy. Postoperatively, the headaches and syncopal episodes resolved in both patients., Conclusion: Endoscopic fenestration of symptomatic septum pellucidum cysts produces immediate relief of the mass effect of the cyst and resolution of associated symptoms. Cannulation of the lateral ventricle before cyst fenestration prevents inadvertent injury to the fornices, thalamus, internal capsule, caudate nucleus, and septal and thalamostriate veins. The endoscopic approach allows the surgeon to ensure communication within the ventricular system, thus avoiding placement of a shunt. Preliminary ultrastructural analysis indicates that the cyst walls derive from the septum pellucidum rather than the choroid plexus or arachnoid. The cellular machinery necessary for fluid secretion was identified in some specimens.

Objective: The ability to visualize median-sagittal brain structures by magnetic resonance imaging improves planning for surgery to treat lesions of the third ventricle. The most appropriate path to the third ventricle is the transcallosal approach. The present study was undertaken to describe the surgical anatomy and landmarks encountered during this approach., Methods: The transcallosal-interforniceal approach was undertaken in 30 formalin-fixed brains using an operating microscope. The surface landmarks for the approach pathway were the two points, P5 and P7, located 5 and 7 cm anterior to the central sulcus, respectively. Using these two points on the cortical surface as references, a variety of measurements were made to provide quantitative information about distances between brain structures that are encountered during the surgical approach. Measurements that were made include the following: 1) the distance between P5 and the cingulate sulcus, 2) the distance between the cingulate sulcus and the corpus callosum, 3) the height of the corpus callosum, 4) the distance between the anterior commissure and the foramen of Monro, and 5) the distance between the lower margin of the corpus callosum and the fornix., Results: Mean values for these key measurements were as follows: 1) 23.96 mm (range, 15.0-32.0 mm); 2) 13.50 mm (range, 8.0-20.0 mm) with reference to P5 and 12.73 mm (range, 16.0-18.0 mm) with reference to P7; 3) 6.12 mm (range, 4.0-8.0 mm) with reference to P5 and 6.60 mm (range, 4.0-9.0 mm) with reference to P7; 4) 4.96 mm (range, 2.5-10.0 mm), independent of P5 and P7; and 5) 8.46 mm (range, 3.0-16.0 mm) with reference to P5 and 11.04 mm (range, 6.0-22.0 mm) with reference to P7., Conclusion: The detailed quantitative information obtained in this study about the interforniceal approach permitted definition of surgical approach pathways that preserve important anatomic structures, such as the motor strip, genu of the corpus callosum, fornical commissure (hippocampal commissure), anterior commissure, and fornical columns. The approach through this surgical corridor can easily be planned and performed in individual cases using median-sagittal magnetic resonance imaging scans.

A 63-year-old man was admitted to our hospital because of loss of memory, disorientation, nausea, and urinary incontinence. Cerebral computed tomographic and magnetic resonance imaging scans revealed a tumor with intratumoral hemorrhage affecting the corpus callosum and the septum pellucidum. A partial resection of the tumor was performed, but the patient died the next day from an episode of bleeding. Postmortem examination revealed a highly vascularized subependymoma with acute bleeding in the tumor and in the surrounding brain parenchyma. The importance of considering a highly vascularized subependymoma is noted when a tumor related to the ventricular system is diagnosed.

The clinical and histopathological features of 19 patients with tumors involving the septum pellucidum are presented. These tumors predominantly affected young adults, and the clinical manifestations were usually the results of raised intracranial pressure related to obstructive hydrocephalus, mental abnormality, epileptic seizures, or a combination of these. Seventeen of the tumors grew mainly in the lateral and third ventricles, and the other 2 grew both into the lateral ventricle and the cerebral parenchyma. The direction of cellular differentiation of the tumor cells varied from patient to patient and consisted of 8 neurocytomas, 1 mature neuronal tumor with ganglionic and small round neuronal cells, 3 subependymomas, 3 subependymal giant cell astrocytomas, 2 pilocytic astrocytomas, 1 malignant astrocytoma, and 1 teratoma with embryonal carcinoma. These tumors were considered to have arisen from the multipotential cells in the subependymal plate or germ cell rests in the lateral ventricular wall, especially in the septum pellucidum. Because of the relatively inert biological behavior and histological features of most of these tumors, we favor the malformative theory of their origin. Either total or an extensive excision of the tumors in this series, which had developed mainly in the ventricular system, provided long-term survival in many cases.

A "caval-septal" hematoma shown by computed tomography has been described in cases of ruptured aneurysms arising from the anterior communicating artery. This term seems to imply that the hematoma is confined to the cavum septi pellucidi. This common findings almost always represents a hematoma in the anterior interhemispheric fissure.

The oligodendroglioma is an infrequent cerebral tumor of glial ancestry. It is even rarer when primarily arising within the confines of the ventricles and particularly if originating from the septum pellucidum. A 22-year-old man harboring a primary oligodendroglioma of the septum pellucidum was successfully treated by intraventricular tumor removal through a left transcortical-transventricular approach, using microsurgical technique. A brief review of relevant data about both intraventricular oligodendrogliomas and tumors of the septum pellucidum is presented.