Hierarchical structure from motion optical flow algorithms to harvest three-dimensional features from two-dimensional neuro-endoscopic images.

Technical advances have led to an increase in the use of the endoscope in neurosurgery in recent years, particularly for intraventricular procedures and pituitary and anterior skull base surgery. Recently stereoscopic three-dimensional (3D) endoscopes have become available and may over time replace traditional two-dimensional (2D) imagery. An alternative strategy would be to use computer software algorithms to give monocular 2D endoscopes 3D capabilities. In this study our objective was to recover depth information from 2D endoscopic images using optical flow techniques. Digital images were recorded using a 2D endoscope and a hierarchical structure from motion algorithm was applied to the motion of the endoscope in order to calculate depth information for the generation of 3D anatomical structure. We demonstrate that 3D data can be recovered from 2D endoscopic images taken during endoventricular surgery where there is a mix of rapid camera motion and periods where the camera is nearly stationary. These algorithms may have the potential to give 3D visualization capabilities to 2D endoscopic hardware.

Transventricular fenestration of the lamina terminalis: the value of a flexible endoscope: technical note.

BACKGROUND: Recently, the authors demonstrated the technical feasibility of a transventricular translaminar terminalis ventriculostomy with a rigid endoscope. A major problem with this technique remains the contusion of the fornix at the foramen of Monro. Here, the authors evaluated alternative approaches and techniques, including the use of a flexible endoscope. MATERIAL AND METHODS: Feasibility of two approaches-anterior and posterior of the coronal suture-was evaluated on magnetic resonance images and in cadaveric brains. Two different trajectories were selected. Lamina terminalis (LT) fenestration was performed with a rigid and a flexible endoscope using two approaches in 10 fixed cadaver brains. RESULTS: Using the posterior approach 2 cm behind the coronal suture with the two endoscopes caused moderate to severe damage to foramen and fornix. Using the standard approach (Kocher point) with the flexible endoscope avoided damage of these structures. After completion of the anatomical investigation, the authors successfully performed a transventricular fenestration of the LT with the flexible endoscope in one clinical case. CONCLUSION: Rigid scopes provide brilliant optics and safe manipulation with the instruments. However, with the rigid scope, a transventricular opening of the LT is only possible with acceptance of structural damage to the foramen of Monro and the fornix. In contrast, opening of the LT via a transventricular route with preservation of the anatomical structures can be achieved with a flexible steerable endoscope even via a standard burr hole. Thus, if a standard third ventriculostomy is not feasible, endoscopic opening of the LT might represent an alternative, particularly with a flexible scope in experienced hands.

Use of a micromanipulator system (NeuRobot) in endoscopic neurosurgery.

NeuRobot, a micromanipulator system with a rigid neuroendoscope and three micromanipulators, was developed for less invasive and telecontrolled neurosurgery. This system can be used to perform sophisticated surgical procedures through a small, 10-mm-diameter, window. The present study was performed to evaluate the feasibility of using NeuRobot in neuroendoscopy. Four different intraventricular neurosurgical procedures were simulated in three fixed cadaver heads using NeuRobot: (1) fenestration of the floor of the third ventricle; (2) fenestration of the septum pellucidum; (3) biopsy of the thalamus; and (4) biopsy of the choroid plexus of the lateral ventricle. Each procedure required less than 2 min, and all procedures were performed accurately. After these surgical simulations, a third ventriculostomy was carried out safely and adequately in a patient with obstructive hydrocephalus due to a midbrain venous angioma. Our results confirmed that NeuRobot is applicable to lesions in which conventional endoscopic neurosurgery is indicated. Furthermore, NeuRobot can perform more complex surgical procedures than a conventional neuroendoscope because of its maneuverability and stability. NeuRobot will become a useful neurosurgical tool for dealing with lesions that are difficult to treat by conventional neuroendoscopic surgery.

Anterior interhemispheric approach for 100 tumors in and around the anterior third ventricle.

OBJECTIVE: We report our experience with anterior interhemispheric approach for tumors in and around the anterior third ventricle, including surgical technique, instrumentation, pre- and postoperative hormonal disturbances, and resection rate. METHODS: One hundred patients with 46 craniopharyngiomas, 12 hypothalamic gliomas, 12 meningiomas, 6 hypothalamic hamartomas, and 24 other lesions were operated on using an anterior interhemispheric approach with or without opening of the lamina terminalis. This surgical approach involves no frontal sinus opening; a narrow (approximately 15-20 mm in width) access between the bridging veins, which is sufficient to remove the tumor totally; and sparing of the anterior communicating artery. Specially designed long bipolar forceps and scissors are necessary for this approach, and concomitant use of angled instruments (endoscope, aspirator, and microforceps) is required frequently. The postsurgical follow-up period varied from 4 months to 18 years. RESULTS: Total removal of the neoplasm was accomplished in 37 of 46 patients with craniopharyngiomas (80.4%), whereas subtotal resection was performed in hypothalamic gliomas. No significant differences in pre- and postoperative hormonal disturbances were observed in 37 craniopharyngiomas and 10 hypothalamic gliomas. There was no operative mortality. Visual acuity was preserved or improved in 68 of 75 patients assessed. The Karnofsky Performance Scale score did not deteriorate in 72 of 75 patients tested. CONCLUSION: The minimally invasive anterior interhemispheric approach, with or without opening of the lamina terminalis, is useful for removal of tumors in and around the anterior third ventricle, such as craniopharyngiomas and hypothalamic gliomas.

A simplified endoscopic third ventriculostomy under local anesthesia.

The aim of this study is the analysis of our experience with awake endoscopic third ventriculostomy (ETVS) in hydrocephalic patients. From September 1994 to December 2001, 24 neuroendoscopic procedures were performed under local anesthesia. Local infiltration was administered using a bupivacaine and lidocaine mixture. Analgesics were titrated to the effect. A free-hand technique with a flexible endoscope was adopted in 24 patients with primitive and secondary (neoplastic) hydrocephalus. ETVS was performed successfully in all cases. No procedure needed to be discontinued due to seizures, bleeding or agitation. Dural incision/coagulation and Fogarty dilatation proved to be the most painful maneuvers requiring, sometimes, supplemental analgesic administration. No intraoperative complications were observed; however, two asymptomatic trajectory hematomas were incidentally discovered two and three days after the operation, respectively. Awake ETVS is a valuable alternative procedure that can be adopted in adult cooperative patients, provided that the procedure is done in an essential and fast way with the free-hand technique, by means of a flexible endoscope, and with the assistance of an anesthesiologist.