Vestibular Function Tests: A number of tests used to determine if the brain or balance portion of the inner ear are causing dizziness.Vestibular Diseases: Pathological processes of the VESTIBULAR LABYRINTH which contains part of the balancing apparatus. Patients with vestibular diseases show instability and are at risk of frequent falls.Electronystagmography: Recording of nystagmus based on changes in the electrical field surrounding the eye produced by the difference in potential between the cornea and the retina.Vestibule, Labyrinth: An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony COCHLEA anteriorly, and SEMICIRCULAR CANALS posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the STAPES of the MIDDLE EAR.Caloric Tests: Elicitation of a rotatory nystagmus by stimulating the semicircular canals with water or air which is above or below body temperature. In warm caloric stimulation a rotatory nystagmus is developed toward the side of the stimulated ear; in cold, away from the stimulated side. Absence of nystagmus indicates the labyrinth is not functioning.Reflex, Vestibulo-Ocular: A reflex wherein impulses are conveyed from the cupulas of the SEMICIRCULAR CANALS and from the OTOLITHIC MEMBRANE of the SACCULE AND UTRICLE via the VESTIBULAR NUCLEI of the BRAIN STEM and the median longitudinal fasciculus to the OCULOMOTOR NERVE nuclei. It functions to maintain a stable retinal image during head rotation by generating appropriate compensatory EYE MOVEMENTS.Semicircular Canals: Three long canals (anterior, posterior, and lateral) of the bony labyrinth. They are set at right angles to each other and are situated posterosuperior to the vestibule of the bony labyrinth (VESTIBULAR LABYRINTH). The semicircular canals have five openings into the vestibule with one shared by the anterior and the posterior canals. Within the canals are the SEMICIRCULAR DUCTS.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)Otolithic Membrane: A gelatinous membrane overlying the acoustic maculae of SACCULE AND UTRICLE. It contains minute crystalline particles (otoliths) of CALCIUM CARBONATE and protein on its outer surface. In response to head movement, the otoliths shift causing distortion of the vestibular hair cells which transduce nerve signals to the BRAIN for interpretation of equilibrium.Labyrinth Diseases: Pathological processes of the inner ear (LABYRINTH) which contains the essential apparatus of hearing (COCHLEA) and balance (SEMICIRCULAR CANALS).Nystagmus, Pathologic: Involuntary movements of the eye that are divided into two types, jerk and pendular. Jerk nystagmus has a slow phase in one direction followed by a corrective fast phase in the opposite direction, and is usually caused by central or peripheral vestibular dysfunction. Pendular nystagmus features oscillations that are of equal velocity in both directions and this condition is often associated with visual loss early in life. (Adams et al., Principles of Neurology, 6th ed, p272)Nystagmus, Physiologic: Involuntary rhythmical movements of the eyes in the normal person. These can be naturally occurring as in end-position (end-point, end-stage, or deviational) nystagmus or induced by the optokinetic drum (NYSTAGMUS, OPTOKINETIC), caloric test, or a rotating chair.Liver Function Tests: Blood tests that are used to evaluate how well a patient's liver is working and also to help diagnose liver conditions.Vestibular Neuronitis: Idiopathic inflammation of the VESTIBULAR NERVE, characterized clinically by the acute or subacute onset of VERTIGO; NAUSEA; and imbalance. The COCHLEAR NERVE is typically spared and HEARING LOSS and TINNITUS do not usually occur. Symptoms usually resolve over a period of days to weeks. (Adams et al., Principles of Neurology, 6th ed, p304)Dizziness: An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness.Acoustic Maculae: The sensory areas on the vertical wall of the saccule and in the floor of the utricle. The hair cells in the maculae are innervated by fibers of the VESTIBULAR NERVE.Stereocilia: Mechanosensing organelles of hair cells which respond to fluid motion or fluid pressure changes. They have various functions in many different animals, but are primarily used in hearing.Vestibular Evoked Myogenic Potentials: Recorded electrical responses from muscles, especially the neck muscles or muscles around the eyes, following stimulation of the EAR VESTIBULE.Respiratory Function Tests: Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc.Hair Cells, Vestibular: Sensory cells in the acoustic maculae with their apical STEREOCILIA embedded in a gelatinous OTOLITHIC MEMBRANE. These hair cells are stimulated by the movement of otolithic membrane, and impulses are transmitted via the VESTIBULAR NERVE to the BRAIN STEM. Hair cells in the saccule and those in the utricle sense linear acceleration in vertical and horizontal directions, respectively.Vestibular Nerve: The vestibular part of the 8th cranial nerve (VESTIBULOCOCHLEAR NERVE). The vestibular nerve fibers arise from neurons of Scarpa's ganglion and project peripherally to vestibular hair cells and centrally to the VESTIBULAR NUCLEI of the BRAIN STEM. These fibers mediate the sense of balance and head position.Usher Syndromes: Autosomal recessive hereditary disorders characterized by congenital SENSORINEURAL HEARING LOSS and RETINITIS PIGMENTOSA. Genetically and symptomatically heterogeneous, clinical classes include type I, type II, and type III. Their severity, age of onset of retinitis pigmentosa and the degree of vestibular dysfunction are variable.