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Endolymphatic Sac: The blind pouch at the end of the endolymphatic duct. It is a storage reservoir for excess ENDOLYMPH, formed by the blood vessels in the membranous labyrinth.Ear Neoplasms: Tumors or cancer of any part of the hearing and equilibrium system of the body (the EXTERNAL EAR, the MIDDLE EAR, and the INNER EAR).Endolymphatic Duct: The part of the membranous labyrinth that traverses the bony vestibular aqueduct and emerges through the bone of posterior cranial fossa (CRANIAL FOSSA, POSTERIOR) where it expands into a blind pouch called the endolymphatic sac.Endolymph: The lymph fluid found in the membranous labyrinth of the ear. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Vestibular Aqueduct: A small bony canal linking the vestibule of the inner ear to the posterior part of the internal surface of the petrous TEMPORAL BONE. It transmits the endolymphatic duct and two small blood vessels.Meniere Disease: A disease of the inner ear (LABYRINTH) that is characterized by fluctuating SENSORINEURAL HEARING LOSS; TINNITUS; episodic VERTIGO; and aural fullness. It is the most common form of endolymphatic hydrops.Labyrinthitis: Inflammation of the inner ear (LABYRINTH).Endolymphatic Hydrops: An accumulation of ENDOLYMPH in the inner ear (LABYRINTH) leading to buildup of pressure and distortion of intralabyrinthine structures, such as COCHLEA and SEMICIRCULAR CANALS. It is characterized by SENSORINEURAL HEARING LOSS; TINNITUS; and sometimes VERTIGO.von Hippel-Lindau Disease: An autosomal dominant disorder caused by mutations in a tumor suppressor gene. This syndrome is characterized by abnormal growth of small blood vessels leading to a host of neoplasms. They include HEMANGIOBLASTOMA in the RETINA; CEREBELLUM; and SPINAL CORD; PHEOCHROMOCYTOMA; pancreatic tumors; and renal cell carcinoma (see CARCINOMA, RENAL CELL). Common clinical signs include HYPERTENSION and neurological dysfunctions.Cerebellopontine Angle: Junction between the cerebellum and the pons.Temporal Bone: Either of a pair of compound bones forming the lateral (left and right) surfaces and base of the skull which contains the organs of hearing. It is a large bone formed by the fusion of parts: the squamous (the flattened anterior-superior part), the tympanic (the curved anterior-inferior part), the mastoid (the irregular posterior portion), and the petrous (the part at the base of the skull).Skull Neoplasms: Neoplasms of the bony part of the skull.Adenocarcinoma, Papillary: An adenocarcinoma containing finger-like processes of vascular connective tissue covered by neoplastic epithelium, projecting into cysts or the cavity of glands or follicles. It occurs most frequently in the ovary and thyroid gland. (Stedman, 25th ed)Ear, Inner: The essential part of the hearing organ consists of two labyrinthine compartments: the bony labyrinthine and the membranous labyrinth. The bony labyrinth is a complex of three interconnecting cavities or spaces (COCHLEA; VESTIBULAR LABYRINTH; and SEMICIRCULAR CANALS) in the TEMPORAL BONE. Within the bony labyrinth lies the membranous labyrinth which is a complex of sacs and tubules (COCHLEAR DUCT; SACCULE AND UTRICLE; and SEMICIRCULAR DUCTS) forming a continuous space enclosed by EPITHELIUM and connective tissue. These spaces are filled with LABYRINTHINE FLUIDS of various compositions.Yolk Sac: The first of four extra-embryonic membranes to form during EMBRYOGENESIS. In REPTILES and BIRDS, it arises from endoderm and mesoderm to incorporate the EGG YOLK into the DIGESTIVE TRACT for nourishing the embryo. In placental MAMMALS, its nutritional function is vestigial; however, it is the source of INTESTINAL MUCOSA; BLOOD CELLS; and GERM CELLS. It is sometimes called the vitelline sac, which should not be confused with the VITELLINE MEMBRANE of the egg.Vertigo: An illusion of movement, either of the external world revolving around the individual or of the individual revolving in space. Vertigo may be associated with disorders of the inner ear (EAR, INNER); VESTIBULAR NERVE; BRAINSTEM; or CEREBRAL CORTEX. Lesions in the TEMPORAL LOBE and PARIETAL LOBE may be associated with FOCAL SEIZURES that may feature vertigo as an ictal manifestation. (From Adams et al., Principles of Neurology, 6th ed, pp300-1)Anion Transport Proteins: Membrane proteins whose primary function is to facilitate the transport of negatively charged molecules (anions) across a biological membrane.Cerebellar Neoplasms: Primary or metastatic neoplasms of the CEREBELLUM. Tumors in this location frequently present with ATAXIA or signs of INTRACRANIAL HYPERTENSION due to obstruction of the fourth ventricle. Common primary cerebellar tumors include fibrillary ASTROCYTOMA and cerebellar HEMANGIOBLASTOMA. The cerebellum is a relatively common site for tumor metastases from the lung, breast, and other distant organs. (From Okazaki & Scheithauer, Atlas of Neuropathology, 1988, p86 and p141)