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The inner ear is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:
The sense of balance or equilibrioception is the perception of balance and spatial orientation. It helps prevent humans and nonhuman animals from falling over when standing or moving. Equilibrioception is the result of a number of sensory systems working together; the eyes, the inner ears, and the body's sense of where it is in space (proprioception) ideally need to be intact.
The semicircular canals are three semicircular interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the lateral, anterior and posterior semicircular canals. They are the part of the bony labyrinth, a periosteum-lined cavity on the petrous part of the temporal bone filled with perilymph.
The vestibulo-ocular reflex (VOR) is a reflex that acts to stabilize gaze during head movement, with eye movement due to activation of the vestibular system, it is also known as the Cervico-ocular reflex. The reflex acts to stabilize images on the retinas of the eye during head movement. Gaze is held steadily on a location by producing eye movements in the direction opposite that of head movement. For example, when the head moves to the right, the eyes move to the left, meaning the image a person sees stays the same even though the head has turned. Since slight head movement is present all the time, VOR is necessary for stabilizing vision: people with an impaired reflex find it difficult to read using print, because the eyes do not stabilise during small head tremors, and also because damage to reflex can cause nystagmus.
The utricle and saccule are the two otolith organs in the vertebrate inner ear. The word utricle comes from Latin uter 'leather bag'. The utricle and saccule are part of the balancing system in the vestibule of the bony labyrinth. They use small stones and a viscous fluid to stimulate hair cells to detect motion and orientation. The utricle detects linear accelerations and head-tilts in the horizontal plane.
The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear in most mammals.
Spatial disorientation is the inability to determine position or relative motion, commonly occurring during periods of challenging visibility, since vision is the dominant sense for orientation. The auditory system, vestibular system, and proprioceptive system collectively work to coordinate movement with balance, and can also create illusory nonvisual sensations, resulting in spatial disorientation in the absence of strong visual cues.
Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, characterized by a spinning sensation upon changes in the position of the head. This can occur with turning in bed or changing position. Each episode of vertigo typically lasts less than one minute. Nausea is commonly associated. BPPV is one of the most common causes of vertigo.
Electronystagmography (ENG) is a diagnostic test to record involuntary movements of the eye caused by a condition known as nystagmus. It can also be used to diagnose the cause of vertigo, dizziness or balance dysfunction by testing the vestibular system. Electronystagmography is used to assess voluntary and involuntary eye movements. It evaluates the cochlear nerve and the oculomotor nerve. The ENG can be used to determine the origin of various eye and ear disorders.
Vertigo is a condition in which a person has the sensation that they are moving, or that objects around them are moving, when they are not. Often it feels like a spinning or swaying movement. It may be associated with nausea, vomiting, perspiration, or difficulties walking. It is typically worse when the head is moved. Vertigo is the most common type of dizziness.
The vestibular nerve is one of the two branches of the vestibulocochlear nerve. In humans the vestibular nerve transmits sensory information from vestibular hair cells located in the two otolith organs and the three semicircular canals via the vestibular ganglion of Scarpa. Information from the otolith organs reflects gravity and linear accelerations of the head. Information from the semicircular canals reflects rotational movement of the head. Both are necessary for the sensation of body position and gaze stability in relation to a moving environment.
In medicine, the caloric reflex test is a test of the vestibulo-ocular reflex that involves irrigating cold or warm water or air into the external auditory canal. This method was developed by Robert Bárány, who won a Nobel prize in 1914 for this discovery.
The ampullary cupula, or cupula, is a structure in the vestibular system, providing the sense of spatial orientation.
The otolithic membrane is a fibrous structure located in the vestibular system of the inner ear. It plays a critical role in the brain's interpretation of equilibrium. The membrane serves to determine if the body or the head is tilted, in addition to the linear acceleration of the body. The linear acceleration could be in the horizontal direction as in a moving car or vertical acceleration such as that felt when an elevator moves up or down.
The Dix–Hallpike or Nylén–Bárány test is a diagnostic maneuver from the group of rotation tests used to identify benign paroxysmal positional vertigo (BPPV).
The Epley maneuver or repositioning maneuver is a maneuver used by medical professionals to treat one common cause of vertigo, benign paroxysmal positional vertigo (BPPV) of the posterior or anterior canals of the ear. The maneuver works by allowing free-floating particles, displaced otoconia, from the affected semicircular canal to be relocated by using gravity, back into the utricle, where they can no longer stimulate the cupula, therefore relieving the patient of bothersome vertigo. The maneuver was developed by the physician John M. Epley, and was first described in 1980.
Nystagmus is a condition of involuntary eye movement. People can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision.
The righting reflex, also known as the labyrinthine righting reflex, or the Cervico-collic reflex; is a reflex that corrects the orientation of the body when it is taken out of its normal upright position. It is initiated by the vestibular system, which detects that the body is not erect and causes the head to move back into position as the rest of the body follows. The perception of head movement involves the body sensing linear acceleration or the force of gravity through the otoliths, and angular acceleration through the semicircular canals. The reflex uses a combination of visual system inputs, vestibular inputs, and somatosensory inputs to make postural adjustments when the body becomes displaced from its normal vertical position. These inputs are used to create what is called an efference copy. This means that the brain makes comparisons in the cerebellum between expected posture and perceived posture, and corrects for the difference. The reflex takes 6 or 7 weeks to perfect, but can be affected by various types of balance disorders.
Field sobriety tests (FSTs), also referred to as standardized field sobriety tests (SFSTs), are a battery of tests used by police officers to determine if a person suspected of impaired driving is intoxicated with alcohol or other drugs. FSTs are primarily used in the United States, to meet "probable cause for arrest" requirements, necessary to sustain an alcohol-impaired driving conviction based on a chemical blood alcohol test.
Vestibular rehabilitation (VR), also known as vestibular rehabilitation therapy (VRT), is a specialized form of physical therapy used to treat vestibular disorders or symptoms, characterized by dizziness, vertigo, imbalance, posture, and vision. These primary symptoms can result in secondary symptoms such as nausea, fatigue, and difficulty concentrating. Symptoms of vestibular dysfunction can significantly decrease quality of life, introducing mental-emotional issues such as anxiety and depression, and greatly impair an individual, causing them to become more sedentary. Decreased mobility can result in weaker muscles, less flexible joints, and worsened stamina, as well as decreased social and occupational activity. Vestibular rehabilitation therapy can be used in conjunction with cognitive behavioral therapy in order to reduce anxiety and depression resulting from a change in lifestyle.
References
- ↑ K. E. Money; W. S. Myles (8 February 1974). "Heavy water nystagmus and effects of alcohol". Nature. 247 (5440): 404–405. Bibcode:1974Natur.247..404M. doi:10.1038/247404a0. PMID 4544739. S2CID 4166559.
- ↑ Karch, Steven B. (2007). Forensic Issues in Alcohol Testing. Boca Raton: CRC Press. ISBN 978-1-4200-5445-3.
- ↑ Klinik des Gleichgewichts - Prof. Dr. med. Stefan Hegemann
- ↑ Ahr, C. Jonathan (1975). The Relationship Between Positional Alcohol Nystagmus and Accuracy of Estimation of Blood Alcohol. University at Greensboro.
- ↑ Klinik des Gleichgewichts - Prof. Dr. med. Stefan Hegemann
- ↑ Fregly AR, Bergstedt M, Graybiel A (1968). "Relationships between blood alcohol, positional alcohol nystagmus and postural equilibrium". Q J Stud Alcohol. 28 (1): 11–21. doi:10.15288/qjsa.1967.28.011. PMID 5339889.
- ↑ Advanced DUI Investigation: A Training and Reference Manual, Daniel J. Haggin, Charles C Thomas (Publisher), 2005, pg. 144.