Review Journals: Vol 9, Issue 7

1. CPA Vascular Loop and Unilateral SNHL

This interesting study from Scotland (Gorrie, Warren, de La Garza et al, Otology & Neurotology 31(1): January 2010) examined the correlation between vascular loop in the cereellopontine angle and unilateral hearing loss, and observe no correlation, except in subset where the loop is between Facial nerve and vestibular nerve.

Abstract

Objective: This study was a retrospective analysis of patients who had received magnetic resonance imaging scans of the internal auditory canal (IAC) to evaluate unexplained asymmetric hearing loss. The study aimed to correlate structural features of vascular loops formed by the anterior inferior cerebellar artery (AICA) within the cerebellopontine angle and IAC  with asymmetric hearing loss.

Study Design: High-resolution thin-section T2 fast spin echo magnetic resonance imaging scans of 58 patients with asymmetric sensorineural hearing loss were obtained; the structure of the AICA was graded on both sides using 2 scoring systems. The grading senior head and neck radiologist was blinded to the clinical history. The first scoring system used was the Chavda classification, which is based on the anatomic location of the AICA loop. This system identified 92 loops within the cerebellopontine angle; 22 loops extending less than halfway into the IAC and 2 loops extending more than halfway into the IAC. A second classification system was used simultaneously to describe the extent of contact between the AICA loop and the vestibulocochlear nerve. The second system identified 24 loops that were not in contact with the nerve, 60 in which the loop was running adjacent to the nerve but not displacing it; 12 loops were identified that were displacing the vestibulocochlear nerve, and 24 loops were identified running between the facial and the vestibulocochlear nerve. Four loops were classified as both displacing the vestibulocochlear nerve and running between the facial and vestibulocochlear nerves. Tinnitus was present in addition to hearing loss. In 48 of the 58 patients, the statistical analysis was repeated for these patients.

Results: No statistically significant association was found between loops classified by the Chavda system and hearing loss. No statistically significant association was present between loops that made no contact with the nerve, ran adjacent to the nerve, or displaced the nerve. A statistically significant association was found between loops that ran between the facial and vestibulocochlear nerve and hearing loss, with a p value of 0.0162. The subset who had tinnitus in addition to hearing loss had similar results, with the only significant association being found between loops running between the facial nerve and the vestibulocochlear nerve, and a p value of 0.0433 was obtained.

Conclusion: A correlation between vascular loops and hearing loss did not exist in the majority of the patients in this study. The subset of patients that had a vessel between the facial and vestibular cochlear nerves deserve further investigation

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2. Update on Morphology of Incudo-mallear joint Development

This human temporal bone study from Spain (Cisnero Gimeno AI et al, Acta Oto-Laryngologica, Volume 129, Issue 12 December 2009 , pages 1380 – 1387) focused on the ontogeny and development of the incudo-mallear (I-M) joint using histological sections of human embryo and fetuses from 9mm to newborn, and concluded that human I-M joint is fully developed at birth.

Abstract

Conclusion: At the time of birth, the incudo-mallear joint is completely developed. Objective. To study the development of the incudo-mallear joint in human embryos and fetuses. Materials and methods. In all, 46 temporal bones with ages between 9 mm and newborns were studied. The preparations were cut in a series and dyed using Martins’ trichrome technique. Results. The incudo-mallear joint acquires the characteristics of a saddle joint at 10 weeks of development. The cartilage that covers the articular surfaces is formed by different strata that develop successively: the superficial stratum at 14 weeks, the transitional between 15 and 19 weeks, and the radial from 20 weeks. The subchondral bone develops between weeks 25 and 28 by the mechanisms of apposition and extension of the periosteal and endosteal bones, but it is not until week 30 that it completely covers the articular surfaces, consisting of bone fascicles whereby the lines of force will be transmitted. The articular capsule is formed as from the inter-zone. The surface zone develops the capsular ligament, and the internal surface develops the synovial membrane. Even though it is not consistent, the primordium of the meniscus is seen at 18 weeks.

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3. Subjective Visual Vertical (SVV)

This seminar from Tenesse, USA (Akin FW & Murnanae OD, Semin Hear 2009;30:281–286) is aimed at clinicians with the objective of imparting the knowledge of subjective visual vertical in vestibular function assessment, as well as compare and contrast the methods of stimulating the otolith functions during the SVV testing

Abstract

The otoliths are vestibular organs that act as gravito-inertial force sensors and contribute to the perception of spatial orientation (earth verticality). The subjective visual vertical (SVV) is a psychophysical measure of the angle between perceptual vertical and true (gravitational) vertical. The otoliths contribute to the estimation of the physical vertical orientation, and individuals with normal vestibular function align the SVV within 2 degrees of true vertical (0 degrees).

ImpairedSVVhas been documented in patientswith unilateral vestibular disorders. Most research has focused on measuring the static SVV (head upright and stationary); however, more recently, methods have been developed to measure the SVV during stimulation of the otolith organs using on-axis yaw rotation (bilateral centrifugation), off-axis eccentric rotation (unilateral centrifugation), or head tilt for tests of bilateral or unilateral otolith function. The SVV test may be a useful method to assess utricular function in patients complaining of dizziness and/or imbalance and identify stages of recovery for otolith involvement.

KEYWORDS: Vestibular, otolith organs, utricle, subjective visual vertical Learning

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SHORT PUT

“…With these thoughts in mind, I question the ways in which scientific material is distributed today. In an era in which information evolves daily and travels instantaneously, why do we continue to invite authors to contribute to a textbook that is published months to years after the contributions are prepared? How can we improve the process by which scientific data collected are distributed publicly? Why perpetuate a system of scientific funding that encourages already having completed the experiments proposed in the grant application, thereby prolonging the period between data analysis and distribution? Clearly we need to reevaluate our methods of scientific communication in the digital age in which information can be distributed in seconds, rather than months…”

Charles J. Limb, MD: Moving at the Speed of Sound: Scientific Innovation in Auditory ResearchTrends in Amplification, Volume 13 Number 3,September 2009 147-148