Ménière's disease is a disorder that can affect both equilibrium and audition in a variety of ways. Damage to structures near the two nuclei can result in deficits to one or both systems.īalance or hearing deficits may be the result of damage to the middle or inner ear structures. Deficits in one or both systems could occur from damage that encompasses structures close to both. Though they are part of distinct sensory systems, the vestibular nuclei and the cochlear nuclei are close neighbors with adjacent inputs. They both emerge from the inner ear, pass through the internal auditory meatus, and synapse in nuclei of the superior medulla. The sensory nerves from these two structures travel side-by-side as the vestibulocochlear nerve, though they are really separate divisions. The cochlea is responsible for transducing sound waves into a neural signal. The vestibule is the portion for equilibrium, composed of the utricle, saccule, and the three semicircular canals.
Within the petrous region of the temporal bone is the bony labyrinth of the inner ear. Problems with balance, such as vertigo, and deficits in hearing may both point to problems with the inner ear. Though the two senses are not directly related, anatomy is mirrored in the two systems. The vestibulocochlear nerve (CN VIII) carries both equilibrium and auditory sensations from the inner ear to the medulla. Those fibers are conveying peripheral visual information to the opposite side of the brain, so the patient will experience “tunnel vision”-meaning that only the central visual field will be perceived. If the pituitary gland develops a tumor, it can press against the fibers crossing in the chiasm. The pituitary gland is located in the sella turcica of the sphenoid bone within the cranial floor, placing it immediately inferior to the optic chiasm.
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