1/13. Sudden bilateral hearing loss and sporadic mitochondrial dna deletion.Several studies have indicated that a number of different mitochondrial dna (mtDNA) mutations may be responsible for human pathologies. Sensorineural hearing loss (SNHL) may be associated with known syndromes (syndromal SNHL) or represent the only manifestation of mitochondrial damage (non-syndromal hearing loss). Moreover, mtDNA alterations may be responsible for aminoglycoside-induced deafness. We describe a patient harbouring a single sporadic mtDNA deletion, who presented with sudden adult-onset bilateral, although non-simultaneous SNHL, that was partially responsive to corticosteroids. Increased values of rest, and exercise, blood lactic acid were decisive for diagnosis, prompting muscle biopsy that revealed the mtDNA deletion. The case underscores the importance of investigating a mitochondrial disease in cases of SNHL of unknown origin and points out the importance of an increased blood level of lactic acid as a screening test.- - - - - - - - - - ranking = 1keywords = acid (Clic here for more details about this article) |
2/13. Listeners who prefer monaural to binaural hearing aids.Four patients who preferred monaural as compared with binaural amplification were evaluated. For these patients, audiometric data, recognition performance on a dichotic digit task, and monaural and binaural hearing aid performance using four amplification strategies (National Acoustic laboratories-Revised, a speech in noise algorithm, multiple-microphone arrays, and frequency modulated [FM]) are described.The results of dichotic testing using a one-, two-, and three-pair dichotic digit task in free- and directed-recall conditions indicated a left-ear deficit for all subjects that could not be explained by peripheral auditory findings or by a cognitive-based deficit. The results of soundfield testing using a speech in multitalker babble paradigm indicated that when listening in noise, there was little difference between aided and unaided word-recognition performance, suggesting that the binaural hearing aids originally fit for each patient were not providing substantial benefit when listening in a competing babble background. Word-recognition performance when aided monaurally in the right ear was superior to performance when aided monaurally in the left ear and when aided binaurally. The only successful binaural amplification strategy was the FM system. The results indicate that listeners with an auditory-based deficit in dichotic listening may function better with a monaural hearing aid fitting or with an assistive listening device such as an FM system. The findings also suggest that a test of dichotic listening is an important component in the evaluation of patients being considered for amplification.- - - - - - - - - - ranking = 71579.164219174keywords = amplification (Clic here for more details about this article) |
3/13. Multisystem disorder associated with a missense mutation in the mitochondrial cytochrome b gene.Mitochondrial cytochrome b mutations have been reported to have a homogenous phenotype of pure exercise intolerance. We describe a novel mutation in the cytochrome b gene of mitochondrial dna (A15579G) associated with a selective decrease of muscle complex III activity in a patient who, besides severe exercise intolerance, also has multisystem manifestations (deafness, mental retardation, retinitis pigmentosa, cataract, growth retardation, epilepsy). The point mutation is heteroplasmic in muscle (88%) and leukocytes (15%), and changes a highly conserved tyrosine to cysteine at amino acid position 278.- - - - - - - - - - ranking = 0.5keywords = acid (Clic here for more details about this article) |
4/13. Bilateral pheochromocytomas and congenital anomalies associated with a de novo germline mutation in the von Hippel-Lindau gene.A 12-year-old boy presented with severe hypertension, congenital microcephaly, severe hearing loss, developmental delay, cryptorchidism, and bilateral pheochromocytomas, without the phenotypic features of multiple endocrine neoplasia type II syndromes (MEN-2). sequence analysis of the polymerase chain reaction (PCR)-amplified gnomic dna identified a missense mutation at nucleotide 451 of the von Hippel-Lindau (VHL) gene (A451G) that changes a codon for serine (AGT) to one for glycine (GGT) at amino acid position 80 (S80G). The sequence dna analysis of the parents did not show a mutation in the VHL gene that was previously identified in their affected son. The observed constellation of microcephaly, deafness, cryptorchidism, developmental delay, hypertension, and bilateral pheochromocytoma in association with a VHL mutation A451G in a patient with negative family history has not previously been described in the literature. knowledge that VHL mutation plays a critical role in sporadic pheochromocytoma should aid in the future diagnosis and treatment of this tumor. genetic testing in known pheochromocytoma families is indicated to identify genetically abnormal subjects that carry the MEN-2, VHL, and glomus tumor gene mutations.- - - - - - - - - - ranking = 0.5keywords = acid (Clic here for more details about this article) |
5/13. Bilateral amplification for the elderly: are two aids better than one?This paper reviews the advantages and disadvantages of bilateral amplification as opposed to unilateral hearing use for older persons with bilateral symmetric hearing loss. Binaural advantages, such as improved localization and speech recognition in noise, are presented as they pertain to the older population. In addition, contraindications, such as binaural interference, increased costs, cosmetic concerns, decreased manipulation skills, and additional hearing aid management issues, are discussed. A case study is provided in which unilateral hearing aid fitting was more beneficial to a patient than two hearing aids. It is concluded that bilateral amplification should be attempted for all elderly patients with symmetric hearing loss, unless a contraindication is suspected.- - - - - - - - - - ranking = 107368.74632876keywords = amplification (Clic here for more details about this article) |
6/13. biotinidase deficiency: the importance of adequate follow-up for an inconclusive newborn screening result.biotinidase deficiency is an inherited metabolic disorder characterized by inability to recycle protein-bound biotin. It usually presents with ataxia and seizures, though atypical presentations have also been described. We report a 15-month-old boy with profound biotinidase deficiency who presented with laryngeal stridor and subsequently developed severe ataxia and lactic acidosis. Subsequently, it was discovered that the patient's newborn screening test for biotinidase activity had been inconclusive, but confirmatory testing had not been done. brain magnetic resonance imaging showed multiple white matter non-enhancing T2 hyperintensities, which largely resolved following 6 months of biotin therapy; however, there was residual deafness and mental retardation. CONCLUSION: An argument is made for universal newborn screening in biotinidase deficiency and improved mechanisms for follow-up of positive screens, because delay in diagnosis results in irreversible morbidity, newborn screening is cost effective, and early therapy prevents the neurologic sequelae.- - - - - - - - - - ranking = 0.5keywords = acid (Clic here for more details about this article) |
7/13. cochlear implantation in a patient with profound hearing loss with the A1555G mitochondrial dna mutation and no history of aminoglycoside exposure.The A1555G mitochondrial deoxyribonucleic acid (mtDNA) point mutation has classically been associated with sensorineural hearing loss in patients following aminoglycoside exposure. More recently, the mutation has been implicated in sensorineural hearing loss in patients without previous aminoglycoside use. In addition, cochlear implantation has been shown to be effective in the group of patients with prior aminoglycoside exposure but, to date, no case of cochlear implantation in a patient with the A1555G mutation and no prior exposure to aminoglycosides has been explicitly described in the literature. We report the case of an 80-year-old woman with the A1555G mtDNA mutation, a 35-year history of bilateral progressive hearing loss and no history of aminoglycoside exposure who underwent successful implantation of a Nucleus 24 Contour device at our institution. Post-operatively, the patient exhibited marked improvement in tests of auditory performance. We conclude that cochlear implantation can be an effective method to restore some sense of hearing in patients with the A1555G mtDNA mutation and sensorineural hearing loss.- - - - - - - - - - ranking = 0.5keywords = acid (Clic here for more details about this article) |
8/13. melas syndrome involving a mother and two children.Three familial cases of MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke) have been reported. We describe a family with four normal sons and an affected mother, son, and daughter. Although mitochondrial inheritance has been proposed, autosomal and X-linked dominant patterns are also possible. This family also illustrates the variability of expression of MELAS. The proband has the full syndrome, while the mother and daughter manifested less severe findings. All three did not develop symptoms until adulthood.- - - - - - - - - - ranking = 0.5keywords = acid (Clic here for more details about this article) |
9/13. Multichannel syllabic compression for severely impaired listeners.Two listeners with congenital hearing losses characterized by flat audiograms and dynamic ranges of 18-33 dB were tested with three compression systems and one (reference) linear amplification system. The compression systems placed progressively larger amounts of speech energy within the listener's residual dynamic range, by raising to audibility and compressing 25, 50, and 90 percent of the short-term input amplitude distribution in each of 16 frequency bands. The comparison linear system was defined by adjusting six octave-wide bands of speech to comfortable levels. System performance was evaluated with nonsence CVC syllables presented at a constant input level and spoken by two talkers. Extensive training was provided to ensure stable performance. The results were notably speaker-dependent, with compression consistently providing better performance for one speaker, linear amplification for the other. Averaged over speakers, however, there was no net advantage for any of the compression systems for any listener. The use of high compression ratios and large input ranges tended to degrade perception of initial consonants and vowels. Under some conditions, however, final consonant scores were higher with compression than with linear amplification. Compression generally enhanced the distinction between stops and fricatives, but degraded spectral-concentration and relative-intensity cues required to identify place of articulation.- - - - - - - - - - ranking = 53684.37316438keywords = amplification (Clic here for more details about this article) |
10/13. Long-term recovery and no recovery from the auditory deprivation effect with binaural amplification: six cases.Six subjects who developed individually significant auditory deprivation effects associated with monaural amplification were tracked for 6.2 to 15.1 years from the time of their initial hearing aid fitting. Each subject received binaural hearing aids after the auditory deprivation effect became apparent and used binaural amplification for at least 4 years. The findings corroborate and expand upon existing case reports. Several general configurations of recovery and no recovery following the introduction of binaural amplification were identified: (1) cases in which auditory deprivation effects developed within about 2 years and recovered completely within about 2 years of binaural use; (2) cases with significant but incomplete recovery; and (3) cases in which the auditory deprivation effect took several years to develop and did not recover following several years of binaural amplification. Clinical implications of the results are proposed.- - - - - - - - - - ranking = 143158.32843835keywords = amplification (Clic here for more details about this article) |
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