S urgical approaches to the pituitary gland have undergone numerous refinements over the last 100 years. Successful application of the transseptal transsphenoidal approach to the pituitary gland was first described by Hermann Schloffer in 1906. This procedure became the most commonly used approach for resection of pituitary adenomas and is associated with a low rate of morbidity.29 In 1910, Hirsch described a direct endonasal approach to the sphenoid sinus and to the sella, but this technique included resection of the middle turbinate and parts of the nasal septum.19 Halstead published the sublabial gingival approach in the same year.17 In the 1960s and after introduction of the operating microscope, Hardy combined lateral fluoroscopy with microsurgical techniques. This significantly improved magnification and illumination, reduced the risk of brain injury, und increased abbreviatioNs ACTH = adrenocorticotrophic hormone; ENT = ear, nose, and throat; FSH = follicle-stimulating hormone; GH = growth hormone; IGF-1 = insulin-like growth factor-1; LH = luteinizing hormone; TSH = thyroid-stimulating hormone. obJective Over the past 2 decades, endoscopy has become an integral part of the surgical repertoire for skull base procedures. The present clinical evaluation and cadaver study compare binostril and mononostril endoscopic transnasal approaches and the surgical techniques involved. methods Forty patients with pituitary adenomas were treated with either binostril or mononostril endoscopic surgery. Neurosurgical, endocrinological, ophthalmological, and neuroradiological examinations were performed. Ten cadaver specimens were prepared, and surgical aspects of the preparation and neuroradiological examination were documented. results In the clinical evaluation, 0° optics were optimal in the nasal and sphenoidal phase of surgery for both techniques. For detection of tumor remnants, 30° optics were superior. The binostril approach was significantly more time consuming than the mononostril technique. The nasal retractor limited maneuverability of instruments during mononostril approaches in 5 of 20 patients. Endocrinological pituitary function, control of excessive hormone secretion, ophthalmological outcome, residual tumor, and rates of adverse events, such as CSF leaks and diabetes insipidus, were similar in both groups. In the cadaver study, there was no significant difference in the time required for dissection via the binostril or mononostril technique. The panoramic view was superior in the binostril group; this was due to the possibility of wider opening of the sella in the craniocaudal and horizontal directions, but the need for removal of more of the nasal septum was disadvantageous. coNclusioNs Because of maneuverability of instruments and a wider view in the sphenoid sinus, the binostril technique is superior for resection of large tumors with parasellar and suprasellar expansion and tumors requiring extended approaches. The mononostril technique is preferable for tumors with limited extension in the intra- and...