The sellar region and paranasal sinuses constitute the anatomical sections of the skull base in which pathological entities warrant interdisciplinary management. Processes originating in the paranasal sinuses can reach and involve the skull base in and around the sella, sometimes not respecting the natural dural boundary. On the other hand, lesions involving the sellar block, such as pituitary adenomas and meningiomas, can also extend downwards into the paranasal sinuses. The orbit and cavernous sinus may be subject to involvement and infiltration by both paranasal and sellar pathology. The advancement and new achievements of modern diagnostic procedures, such as high-resolution CT, three-dimensional reconstruc­ tion, MRI, and MRI angiography, as well as the detailed selective angiographic protocols and endovascular techniques, have increased the possibilities for surgical management of this type of pathology with extra- and intracranial involvement. Long-standing and intense inter­ disciplinary work has led to sophisticated operative approaches which for benign tumors allow total excision with preservation of structures and function, and for some malignant lesions permit an en bloc resec­ tion via a combined intracranial-extracranial approach. This volume reflects the work and scientific exchange which took place during the IV International Congress of the Skull Base Study Group, held in Hanover. Leading authorities in the basic sciences including anatomy joined with diagnosticians, clinicians, and surgeons from different fields to evaluate the state of the art of this topic in skull base surgery.