OBJECTIVE: Endoscopes have been commonly used in transsphenoidal surgery to treat pituitary tumors, to compensate for the narrow surgical field. Although many navigation systems have been introduced for neurosurgical procedures, there have been few reports of navigation systems for endoscopic operations. This report presents our recently developed, endoscopic, augmented reality (AR) navigation system. METHODS: The technology is based on the principles of AR environment technology. The system consisted of a rigid endoscope with light-emitting diodes, an optical tracking system, and a controller. The operation of the optical tracking system was based on two sets of infrared light-emitting diodes, which measured the position and orientation of the endoscope relative to the patient's head. We used the system during endonasal transsphenoidal operations to treat pituitary tumors in 12 recent cases. RESULTS: Anatomic, “real,” three-dimensional, virtual images of the tumor and nearby anatomic structures (including the internal carotid arteries, sphenoid sinuses, and optic nerves) were superimposed on real- time endoscopic live images. The system also indicated the positions and directions of the endoscope and the endoscopic beam in three-dimensional magnetic resonance imaging or computed tomographic planes. Furthermore, the colors of the wire-frame images of the tumor changed according to the distance between the tip of the endoscope and the tumor. These features were superior to those of conventional navigation systems, which are available only for operating microscopes. CONCLUSION: The endoscopic AR navigation system allows surgeons to perform accurate, safe, endoscope-assisted operations to treat pituitary tumors; it is particularly useful for reoperations, in which midline landmarks may be absent. We consider the AR navigation system to be a promising tool for safe, minimally invasive, endonasal, transsphenoidal surgery to treat pituitary tumors.

Recent advances in endoscopic surgery have developed an endonasal route suitable for pituitary surgery. The main goal of this article is to evaluate benefits of our endoscope-assisted endonasal trans-sphenoidal microsurgery for pituitary tumors in 215 consecutive cases. The pathological classifications of the 215 cases are as follows: 163 pituitary adenomas, 23 Rathke's cleft cysts, 17 craniopharyngiomas, and 12 others. The patients were surgically treated via the endonasal trans-sphenoidal approach using an operating microscope as the primary instrument for tumor resection. Endoscopes were used to complement the operating microscope in visualization. We compared the new approach to the sublabial trans-sphenoidal approach (197 cases) with respect to endocrinological outcomes and surgical complications. Our endonasal trans-sphenoidal approach was beneficial in eliminating the complications of lip numbness, which was often observed in patients undergoing sublabial surgery, and nasal septal perforation. In addition, endocrinological outcome comparable to those in the sublabial group was achieved in the endonasal group. We consider that the endoscope, which allows visualization of areas not seen with the operating microscope, should be used actively in conjunction with the operating microscope that provides three-dimensional visualization and is timesaving. Our surgical method for pituitary tumors provides good results with minimal invasion, by exploiting the advantages of a microscope and an endoscope.

Cerebral hyperperfusion syndrome is a major complication after carotid endarterectomy (CEA). We investigated whether our strategy of minimizing intraoperative cerebral ischemia and strict postoperative blood pressure control under continuous sedation prevented postoperative hyperperfusion. Eighty consecutive patients undergoing CEA were studied. A shunt was used in all patients during CEA. All patients were managed postoperatively under continuous sedation for as long as 48 hours on the basis of the regional cerebral blood flow (rCBF) measured immediately after CEA. Postoperative hyperperfusion was assessed, on the basis of the cerebral blood flow study under sedation (propofol) after CEA, either as a greater than 30% increase in rCBF compared with the contralateral side, or a greater than 100% increase in the corrected rCBF (calculated from percentage reduction of the contralateral rCBF induced by propofol) compared with preoperative values. No patient developed cerebral hyperperfusion syndrome. Postoperative hyperperfusion was found at very low rates (2.5% in the middle cerebral artery territory and 1.3% in the anterior cerebral artery territory by definition 1, and 0% in both territories by definition 2). Ratios of regional oxygen saturation after internal carotid artery clamping to preclamp baseline values were greater than 0.9 in 78 of 80 patients, indicating very mild intraoperative cerebral ischemia. Parameters related to cerebral ischemia during CEA, such as regional oxygen saturation, internal carotid artery cross-clamping duration, and stump pressure (index), did not affect the incidence of postoperative hyperperfusion. The present study suggests that minimizing intraoperative cerebral ischemia using a shunt, followed by strict postoperative blood pressure control under continuous sedation, can prevent post-CEA hyperperfusion.