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MRI of the inner ear: comparison of axial T2-weighted, three-dimensional turbo spin-echo images, maximum-intensity projections, and volume rendering.

RATIONALE AND OBJECTIVES: To compare the ability of axial T2-weighted, three-dimensional, turbo spin-echo (3D TSE) images, targeted maximum-intensity projections (MIPs), and 3D volume reconstructions to depict anatomic details of the labyrinth. METHODS: In 24 volunteers, 3D TSE images were obtained. MIPs and 3D volume reconstructions were performed from the acquired data. All images were evaluated by three radiologists independently regarding the visualization of the different anatomic structures. RESULTS: In the axial slices, most anatomic details were visible in comparison with observations by the other modalities. The 2.5 windings of the cochlea were best depicted on the MIPs. Volume reconstructions rendered excellent spatial information regarding the vestibule and semicircular canals and were the only technique that demonstrated all three ampullae in all cases. CONCLUSIONS: Axial TSE images, MIPs, and 3D volume reconstructions are complementary modalities that provide different information. Our results suggest that improved diagnostic information can be obtained by applying these volume visualization reconstruction techniques.

Adult↗

Inner ear abnormalities in a Kcnq1 (Kvlqt1) knockout mouse: a model of Jervell and Lange-Nielsen syndrome.

HYPOTHESIS: Mice lacking functional KCNQ1 (previously known as KvLQT1) channels exhibit functional and structural abnormalities that indicate disturbed production of endolymph. BACKGROUND: Congenital deafness associated with cardiac conduction abnormalities (Jervell and Lange-Nielsen syndrome) is associated with dysfunctional KCNQ1/KCNE1 channel complex. This potassium channel plays a critical role in the production and homeostasis of endolymph by the stria vascularis. A preliminary report documented severe abnormalities of the scala media and vestibular compartments of a single mouse lacking functional KCNQ1 alleles. METHODS: Hearing thresholds were measured in three Kcnq1 knockout mice, two heterozygous mice, and one wild-type mouse by auditory brainstem response recordings using clicks, after which the temporal bones were removed. After fixation and dehydration, the ears were embedded in araldite, sectioned at 20-microm thickness, stained with toluidine blue on glass slides, and examined with the light microscope. RESULTS: Kcnq1 knockout mice were deaf and demonstrated circling behavior. They exhibited a marked atrophy of the stria vascularis, contraction of the endolymphatic compartments, and collapse and adhesion of surrounding membranes. There was a complete degeneration of the organ of Corti and an associated degeneration of the spiral ganglion. CONCLUSION: Kcnq1 knockout mice exhibit histopathologic findings that are comparable to those reported in human temporal bone cases of Jervell and Lange-Nielsen syndrome, and provide further evidence that KCNQ1 channel dysfunction can lead to congenital deafness in this syndrome.

Animals↗

Inner ear decompression sickness and mal de debarquement.

OBJECTIVE: To present a case series of vestibular symptoms appearing after combined sailing and diving activity, and to discuss the differential diagnosis and the workup algorithm. STUDY DESIGN: Case series. SETTING: Tertiary referral center. PATIENTS: Three patients aged 25 to 31 years suffering from unsteadiness and movement sensations after sailing and scuba diving. INTERVENTIONS: Neurotologic evaluation and recompression therapy in a hyperbaric chamber. MAIN OUTCOME MEASURES: The increasing popularity of marine sports and leisure activities has resulted in the exposure of a growing number of people to unique abnormalities not encountered under terrestrial conditions. The otolaryngologist who is involved in the care of these patients is required to diagnose and treat diving-related sinus and ear injuries such as barotrauma and decompression sickness, and also to be familiar with sailing-related disorientation syndromes such as seasickness and mal de debarquement. Treatment modalities for the various abnormalities differ significantly, and early commencement of treatment is often crucial for a successful outcome. CONCLUSION: Whenever doubt exists, recompression treatment must be instituted as soon as possible because of the potential for severe sequelae if the patient is left untreated, and because the risks involved in this therapy are minimal.

Adult↗

Cochlear potentials of the pigeon inner ear recorded with microelectrodes.

The CM-intensity function (i.e. the relation between the amplitude of the cochlear potential (CM) and the sound pressure level) of the avian ear has previously been shown to deviate from the mammalian ear with respect to the slope of the linear part of the function. The lower slope values found in the perilymphatic space of the avian ear have been interpreted to indicate a damping influence of the tegmentum vasculosum on the mechanical vibration of the basilar membrane. In this study the CM-intensity function has been examined on either side of the tegmentum vasculosum of the pigeon ear using microelectrode technique. The slope of the linear part of the CM-intensity function in scala vestibuli was found to be a function of the sound frequency approaching unity at higher frequencies. In ductus cochlearis the slope of the linear part of the CM-intensity function was close to unity at most frequencies except the best frequency for the electrode position. At this frequency (3-4 kHz) the slope value was low. These findings from the ductus cochlearis are similar to findings in scala media of the mammalian ear. Thus the influence of tegmentum vasculosum on CM in scala vestibuli may be due to passive electrical properties of the tissue and not to the mechanical vibration of the basilar membrane.

Action Potentials↗