Progressive High-frequency Hearing Loss Research Articles

Generation of an induced pluripotent stem cell line from a late-onset, progressive high frequency hearing loss patient due to mutation in CDH23

Cadherin 23 (CDH23) is one of the most common genes responsible for hereditary hearing loss; a mutation of CDH23 can cause a wide range of symptoms depending on the variant. In this study, an iPSC line was generated from a patient with late-onset, progressive high frequency hearing loss caused by c.[719C > T];[6085C > T]:p.[P240L];[R2029W] compound heterozygous variants of CDH23. The cells were confirmed to have a normal karyotype, express markers of pluripotency, and have tri-embryonic differentiation potential. This disease-specific iPSC line will further the construction of disease models and the elucidation of the pathophysiology of CDH23 mutations.

Altered Fhod3 expression involved in progressive high-frequency hearing loss via dysregulation of actin polymerization stoichiometry in the cuticular plate.

Age-related hearing loss (ARHL) is a common sensory impairment with complex underlying mechanisms. In our previous study, we performed a meta-analysis of genome-wide association studies (GWAS) in mice and identified a novel locus on chromosome 18 associated with ARHL specifically linked to a 32 kHz tone burst stimulus. Consequently, we investigated the role of Formin Homology 2 Domain Containing 3 (Fhod3), a newly discovered candidate gene for ARHL based on the GWAS results. We observed Fhod3 expression in auditory hair cells (HCs) primarily localized at the cuticular plate (CP). To understand the functional implications of Fhod3 in the cochlea, we generated Fhod3 overexpression mice (Pax2-Cre+/-; Fhod3Tg/+) (TG) and HC-specific conditional knockout mice (Atoh1-Cre+/-; Fhod3fl/fl) (KO). Audiological assessments in TG mice demonstrated progressive high-frequency hearing loss, characterized by predominant loss of outer hair cells, and a decreased phalloidin intensities of CP. Ultrastructural analysis revealed loss of the shortest row of stereocilia in the basal turn of the cochlea, and alterations in the cuticular plate surrounding stereocilia rootlets. Importantly, the hearing and HC phenotype in TG mice phenocopied that of the KO mice. These findings suggest that balanced expression of Fhod3 is critical for proper CP and stereocilia structure and function. Further investigation of Fhod3 related hearing impairment mechanisms may lend new insight towards the myriad mechanisms underlying ARHL, which in turn could facilitate the development of therapeutic strategies for ARHL.

Chronic Oral Selegiline Treatment Mitigates Age-Related Hearing Loss in BALB/c Mice.

Age-related hearing loss (ARHL), a sensorineural hearing loss of multifactorial origin, increases its prevalence in aging societies. Besides hearing aids and cochlear implants, there is no FDA approved efficient pharmacotherapy to either cure or prevent ARHL. We hypothesized that selegiline, an antiparkinsonian drug, could be a promising candidate for the treatment due to its complex neuroprotective, antioxidant, antiapoptotic, and dopaminergic neurotransmission enhancing effects. We monitored by repeated Auditory Brainstem Response (ABR) measurements the effect of chronic per os selegiline administration on the hearing function in BALB/c and DBA/2J mice, which strains exhibit moderate and rapid progressive high frequency hearing loss, respectively. The treatments were started at 1 month of age and lasted until almost a year and 5 months of age, respectively. In BALB/c mice, 4 mg/kg selegiline significantly mitigated the progression of ARHL at higher frequencies. Used in a wide dose range (0.15–45 mg/kg), selegiline had no effect in DBA/2J mice. Our results suggest that selegiline can partially preserve the hearing in certain forms of ARHL by alleviating its development. It might also be otoprotective in other mammals or humans.

Synaptojanin2 Mutation Causes Progressive High-frequency Hearing Loss in Mice.

Progressive hearing loss is very common in the human population but we know little about the underlying molecular mechanisms. Synaptojanin2 (Synj2) has been reported to be involved, as a mouse mutation led to a progressive increase in auditory thresholds with age. Synaptojanin2 is a phosphatidylinositol (PI) phosphatase that removes the five-position phosphates from phosphoinositides, such as PIP2 and PIP3, and is a key enzyme in clathrin-mediated endocytosis. To investigate the mechanisms underlying progressive hearing loss, we have studied a different mutation of mouse Synj2 to look for any evidence of involvement of vesicle trafficking particularly affecting the synapses of sensory hair cells. Auditory brainstem responses (ABR) developed normally at first but started to decline between 3 and 4 weeks of age in Synj2tm1b mutants. At 6 weeks old, some evidence of outer hair cell (OHC) stereocilia fusion and degeneration was observed, but this was only seen in the extreme basal turn so cannot explain the raised ABR thresholds that correspond to more apical regions of the cochlear duct. We found no evidence of any defect in inner hair cell (IHC) exocytosis or endocytosis using single hair cell recordings, nor any sign of hair cell synaptic abnormalities. Endocochlear potentials (EP) were normal. The mechanism underlying progressive hearing loss in these mutants remains elusive, but our findings of raised distortion product otoacoustic emission (DPOAE) thresholds and signs of OHC degeneration both suggest an OHC origin for the hearing loss. Synaptojanin2 is not required for normal development of hearing but it is important for its maintenance.

Essential nucleotide- and protein-dependent functions of Actb/β-actin

The highly similar cytoplasmic β- and γ-actins differ by only four functionally similar amino acids, yet previous in vitro and in vivo data suggest that they support unique functions due to striking phenotypic differences between Actb and Actg1 null mouse and cell models. To determine whether the four amino acid variances were responsible for the functional differences between cytoplasmic actins, we gene edited the endogenous mouse Actb locus to translate γ-actin protein. The resulting mice and primary embryonic fibroblasts completely lacked β-actin protein, but were viable and did not present with the most overt and severe cell and organismal phenotypes observed with gene knockout. Nonetheless, the edited mice exhibited progressive high-frequency hearing loss and degeneration of actin-based stereocilia as previously reported for hair cell-specific Actb knockout mice. Thus, β-actin protein is not required for general cellular functions, but is necessary to maintain auditory stereocilia.

Wbp2 is required for normal glutamatergic synapses in the cochlea and is crucial for hearing.

WBP2 encodes the WW domain-binding protein 2 that acts as a transcriptional coactivator for estrogen receptor α (ESR1) and progesterone receptor (PGR). We reported that the loss of Wbp2 expression leads to progressive high-frequency hearing loss in mouse, as well as in two deaf children, each carrying two different variants in the WBP2 gene. The earliest abnormality we detect in Wbp2-deficient mice is a primary defect at inner hair cell afferent synapses. This study defines a new gene involved in the molecular pathway linking hearing impairment to hormonal signalling and provides new therapeutic targets.

The LINC complex is essential for hearing

Hereditary hearing loss is the most common sensory deficit. We determined that progressive high-frequency hearing loss in 2 families of Iraqi Jewish ancestry was due to homozygosity for the protein truncating mutation SYNE4 c.228delAT. SYNE4, a gene not previously associated with hearing loss, encodes nesprin-4 (NESP4), an outer nuclear membrane (ONM) protein expressed in the hair cells of the inner ear. The truncated NESP4 encoded by the families' mutation did not localize to the ONM. NESP4 and SUN domain-containing protein 1 (SUN1), which localizes to the inner nuclear membrane (INM), are part of the linker of nucleoskeleton and cytoskeleton (LINC) complex in the nuclear envelope. Mice lacking either Nesp4 or Sun1 were evaluated for hair cell defects and hearing loss. In both Nesp4-/- and Sun1-/- mice, OHCs formed normally, but degenerated as hearing matured, leading to progressive hearing loss. The nuclei of OHCs from mutant mice failed to maintain their basal localization, potentially affecting cell motility and hence the response to sound. These results demonstrate that the LINC complex is essential for viability and normal morphology of OHCs and suggest that the position of the nucleus in sensory epithelial cells is critical for maintenance of normal hearing.

Nucleocytoplasmic connections and deafness

The linker of nucleoskeleton and cytoskeleton (LINC) complex connects the nuclear lamina to the cytoskeleton, in part to aid in nuclear positioning. Mutations in genes encoding LINC complex and lamina components cause a range of human diseases. In this issue of the JCI, Horn et al. report that mutations in the gene SYNE4 encoding the LINC complex protein nesprin-4 lead to progressive high-frequency hearing loss. Further, in mice deficient in nesprin-4 and Sun1, another LINC complex component, outer hair cells of the cochlea form normally during development, but die in the early postnatal weeks. These results link improper nuclear positioning specifically to the death of outer hair cells in the organ of Corti and ultimately to deafness.

A novel DSPPmutation causes dentinogenesis imperfecta type II in a large Mongolian family

BackgroundSeveral studies have shown that the clinical phenotypes of dentinogenesis imperfecta type II (DGI-II) may be caused by mutations in dentin sialophosphoprotein (DSPP). However, no previous studies have documented the clinical phenotype and genetic basis of DGI-II in a Mongolian family from China.MethodsWe identified a large five-generation Mongolian family from China with DGI-II, comprising 64 living family members of whom 22 were affected. Linkage analysis of five polymorphic markers flanking DSPP gene was used to genotype the families and to construct the haplotypes of these families. All five DSPP exons including the intron-exon boundaries were PCR-amplified and sequenced in 48 members of this large family.ResultsAll affected individuals showed discoloration and severe attrition of their teeth, with obliterated pulp chambers and without progressive high frequency hearing loss or skeletal abnormalities. No recombination was found at five polymorphic markers flanking DSPP in the family. Direct DNA sequencing identified a novel A→G transition mutation adjacent to the donor splicing site within intron 3 in all affected individuals but not in the unaffected family members and 50 unrelated Mongolian individuals.ConclusionThis study identified a novel mutation (IVS3+3A→G) in DSPP, which caused DGI-II in a large Mongolian family. This expands the spectrum of mutations leading to DGI-II.

Roles of Alternative Splicing in the Functional Properties of Inner Ear-specific KCNQ4 Channels

The function of the KCNQ4 channel in the auditory setting is crucial to hearing, underpinned by the finding that mutations of the channel result in an autosomal dominant form of nonsyndromic progressive high frequency hearing loss. The precise function of KCNQ4 in the inner ear has not been established. However, recently we demonstrated that there is differential expression among four splice variants of KCNQ4 (KCNQ4_v1-v4) along the tonotopic axis of the cochlea. Alternative splicing specifies the outcome of functional channels by modifying the amino acid sequences within the C terminus at a site designated as the membrane proximal region. We show that variations within the C terminus of splice variants produce profound differences in the voltage-dependent phenotype and functional expression of the channel. KCNQ4_v4 lacks exons 9-11, resulting in deletion of 54 amino acid residues adjacent to the S6 domain compared with KCNQ4_v1. Consequently, the voltage-dependent activation of KCNQ4_v4 is shifted leftward by approximately 20 mV, and the number of functional channels is increased severalfold compared with KCNQ4_v1. The properties of KCNQ4_v2 and KCNQ4_v3 fall between KCNQ4_v1 and KCNQ4_v4. Because of variations in the calmodulin binding domains of the splice variants, the channels are differentially modulated by calmodulin. Co-expression of these splice variants yielded current magnitudes suggesting that the channels are composed of heterotetramers. Indeed, a dominant negative mutant of KCNQ4_v1 cripples the currents of the entire KCNQ4 channel family. Furthermore, the dominant negative KCNQ4 mutant stifles the activity of KCNQ2-5, raising the possibility of a global disruption of KCNQ channel activity and the ensuing auditory phenotype.

Deafness in LIMP2‐deficient mice due to early loss of the potassium channel KCNQ1/KCNE1 in marginal cells of the stria vascularis

Our previous studies revealed a critical role of the lysosomal membrane protein LIMP2 in the regulation of membrane transport processes in the endocytic pathway. Here we show that LIMP2-deficient mice display a progressive high-frequency hearing loss and decreased otoacoustic emissions as early as 4 weeks of age. In temporal overlap to hearing impairment, fluorescence immunohistochemical studies revealed that the potassium channel KCNQ1 and its beta-subunit KCNE1 were almost completely lost in the luminal part of marginal cells in the stria vascularis, affecting first higher and later also lower frequency processing cochlear turns. Concomitant with this, the expression of megalin, a multiligand endocytic receptor, was reduced in luminal surfaces of marginal cells within the stria vascularis. KCNQ1/KCNE1 and megalin were also lost in the dark cells of the vestibular system. Although LIMP2 is normally expressed in all cells of the stria vascularis, in the organ of Corti and cochlear neurons, the lack of LIMP2 preferentially caused a loss of KCNQ1/KCNE1 and megalin, and structural changes were only seen months later, indicating that these proteins are highly sensitive to disturbances in the lysosomal pathway. The spatio-temporal correlation of the loss of KCNQ1/KCNE1 surface expression and loss of hearing thresholds supports the notion that the decline of functional KCNQ1/KCNE1 is likely to be the primary cause of the hearing loss. Our findings suggest an important role for LIMP2 in the control of the localization and the level of apically expressed membrane proteins such as KCNQ1, KCNE1 and megalin in the stria vascularis.

Differential Expression of KCNQ4 in Inner Hair Cells and Sensory Neurons Is the Basis of Progressive High-Frequency Hearing Loss

Human KCNQ4 mutations known as DFNA2 cause non-syndromic, autosomal-dominant, progressive high-frequency hearing loss in which the cellular and molecular basis is unclear. We provide immunofluorescence data showing that Kcnq4 expression in the adult cochlea has both longitudinal (base to apex) and radial (inner to outer hair cells) gradients. The most intense labeling is in outer hair cells at the apex and in inner hair cells as well as spiral ganglion neurons at the base. Spatiotemporal expression studies show increasing intensity of KCNQ4 protein labeling from postnatal day 21 (P21) to P120 mice that is most apparent in inner hair cells of the middle turn. We have identified four alternative splice variants of Kcnq4 in mice. The alternative use of exons 9-11 produces three transcript variants (v1-v3), whereas the fourth variant (v4) skips all three exons; all variants have the same amino acid sequence at the C termini. Both reverse transcription-PCR and quantitative PCR analyses demonstrate that these variants have differential expression patterns along the length of the mouse organ of Corti and spiral ganglion neurons. Our expression data suggest that the primary defect leading to high-frequency loss in DFNA2 patients may be attributable to high levels of the dysfunctional Kcnq4_v3 variant in the spiral ganglion and inner hair cells in the basal hook region. Progressive hearing loss associated with aging may result from an increasing mutational load expansion toward the apex in inner hair cells and spiral ganglion neurons.

Protective effects of α-tocopherol and tiopronin against cisplatin-induced ototoxicity

ObjectiveTo investigate the possible protective effects of α-tocopherol and tiopronin against cisplatin-induced cochlear damage. Cisplatin ototoxicity and nephrotoxicity seem to result from the inhibition of cochlear antioxidant defences, causing an increase in the amount of reactive oxygen species. Antioxidants, such as α-tocopherol and tiopronin, are able to suppress lipid peroxidation, thus attenuating tissue damage. Material and MethodsHartley albino guinea pigs were used. The animals were treated for 7 consecutive days with either (I) cisplatin alone, (II) cisplatin+α-tocopherol acetate, (III) cisplatin+tiopronin, (IV) cisplatin+α-tocopherol acetate+tiopronin, (V) α-tocopherol acetate alone or (VI) tiopronin alone. Changes in cochlear function were characterized by means of compound action potential threshold shifts. After the functional testing, tympanic bullae were removed and processed for morphological examination of the sensorineural epithelium. Renal function was evaluated by measuring serum blood urea nitrogen and creatinine levels. ResultsCisplatin induced progressive high-frequency hearing loss of 40–50 dB SPL. α-Tocopherol and tiopronin co-therapy significantly slowed the progression of hearing loss. Treatment with α-tocopherol acetate or tiopronin alone was less effective. Morphological observations showed an important loss of outer hair cells and degeneration of the organ of Corti in the basal and middle turns. Injection of both α-tocopherol and tiopronin reduced cochlear outer hair cell loss more than treatment with a single drug. Beneficial effects of α-tocopherol and tiopronin on cisplatin-induced nephrotoxicity were observed. Conclusion This study supports the hypothesis that α-tocopherol and tiopronin interfere with cisplatin-induced damage, and suggests that concurrent treatment with the two drugs can be useful in protecting against hearing loss.

α-Tocopherol protective effects on gentamicin ototoxicity: an experimental study

Gentamicin, acting as an iron chelator, activates membrane lipid peroxidation (MPL) and induces free radical formation, as observed in vitro and in vivo. Antioxidants, such as α-tocopherol, are able to suppress MLP, thus attenuating tissue damage. The present study was designed to investigate the possible protective effects of α-tocopherol on gentamicin ototoxicity. The study was carried out on albino guinea pigs (250–350 g). The animals were divided into four groups: group A (n = 4), injected with corn oil daily at a dose of 100 mg/kg body weight intramuscularly (IM); group B (n = 10), treated with corn oil at a dose of 100 mg/kg body weight and gentamicin base at a dose of 100 mg/kg body weight (IM); group C (n = 10), treated with gentamicin alone at a dose of 100 mg/kg body weight (IM); and group D (n 10), treated with gentamicin at the same dose plus α-tocopherol acetate at dose of 100 mg/kg body weight (IM). Electrocochleographic recordings were made from an implanted round-window electrode. All animals were treated for 14 days. The compound action potentials (CAPs) were measured at 2–16 kHz at days 0, 10, 14 and 18 after treatment. Changes in cochlear function were characterized as CAP threshold shifts. Morphological changes were analysed by scanning electron microscopy. Gentamicin induced progressive high-frequency hearing loss of 50–60 dB SPL. α-tocopherol co-therapy slowed the progression of hearing loss. The significant loss of outer hair cells (OHCs) in the cochlear basal turn in gentamicin-treated animals was not observed in the cochleas of animals protected with α-tocopherol. This study supports the hypothesis that α-tocopherol interferes with gentamicin-induced free radical formation, and suggests that this drug may be useful in protecting OHC function from aminoglycoside ototoxicity, thus reducing hearing loss.

Protective Effects of α-Tocopherol Against Gentamicin-induced Oto-vestibulo Toxicity: An Experimental Study

Objective—Free radicals are involved in gentamicin ototoxicity and vestibular dysfunction and it has been demonstrated that free radical scavengers, such as α-tocopherol, are able to inactive free radicals, attenuating tissue damage. This study was designed to investigate the possible protective effects of α-tocopherol against gentamicin-induced oto-vestibulo toxicity.Material and Methods—Adult albino guinea pigs were divided into four groups and were treated for 2 weeks as follows: Group A, controls; Group B, gentamicin plus corn oil; Group C, gentamicin only; and Group D, gentamicin plus α-tocopherol. To evaluate vestibular function, the animals underwent sinusoidal oscillations in the dark about their vertical and longitudinal axes to evoke horizontal and vertical vestibulo-ocular reflexes (VORs), respectively. Electrocochleographic recordings were performed using an implanted round window electrode. The compound action potentials (CAPs) at 2, 4, 8 and 16 kHz were measured every 5 days. Morphological changes were analysed by means of scanning electron microscopy.Results—Gentamicin induced a consistent reduction in VOR responses and a progressive high-frequency hearing loss of 50–60 dB sound pressure level. α-Tocopherol co-therapy slowed the progression of hearing loss and significantly attenuated the final threshold shifts. The impairment of vestibular function was reduced, as evidenced by an increased VOR gain. The massive loss of outer hair cells in the cochlear basal turn and of cristae ampullaris stereocilia in gentamicin-treated animals was not observed in the cochlea of animals protected with α-tocopherol.Conclusion—This study supports the hypothesis that α-tocopherol interferes with gentamicin-induced free radical formation, and suggests that this drug may be useful in preventing aminoglycoside oto-vestibulo toxicity.

Further evidence for a third deafness gene within the DFNA2 locus

DFNA2 is a complex locus. Two hearing loss genes have been identified at this site: GJB3, the gene that encodes the gap junction protein connexin 31, and KCNQ4, a voltage-gated potassium channel gene. A third gene has previously been postulated to explain the hearing loss in an Indonesian family linked to the region but devoid of mutation in either known gene (Van Hauwe et al. [1999: Nat Genet 21:263]). We have identified a large five-generation family with nonsyndromic, autosomal dominant progressive high-frequency hearing loss. The hearing impairment maps to 1p34, the site of the DFNA2 locus. Two-point linkage analysis of microsatellite markers spanning the locus resulted in a lod score of 6.6 at D1S391 at theta = 0. We have investigated both identified deafness genes in affected and unaffected family members and have not found any disease-causing mutations, suggesting that another hearing impairment gene resides at the DFNA2 locus.

Neural plasticity in the mouse inferior colliculus: relationship to hearing loss, augmented acoustic stimulation, and prepulse inhibition

C57BL/6J (C57) and DBA/2J (DBA) mice exhibit progressive high-frequency hearing loss. Extracellular recordings of responses of neurons in the inferior colliculus (IC) evoked by 70-dB SPL tones indicated that normal tonotopic organization was greatly disrupted in both strains: still-audible lower frequencies (4–12 kHz) evoked responses in a large percentage of recording sites in ventral tonotopic regions that normally respond strongly to high frequencies only. To relate the IC responses to an auditory behavior, prepulse inhibition (PPI) was measured using 70-dB tones as prepulses. As high-frequency hearing loss progressed in C57 mice, prepulses of 4–12 kHz elicited stronger PPI, and this was significantly correlated with changes in the percentage of IC recording sites responding to 70-dB tones (the neural pathway for PPI includes the IC). The analysis was extended to DBA mice that had been exposed to an augmented acoustic environment (AAE) – a procedure that improves PPI. In these mice, a higher percentage of IC recording sites responded to 70-dB tones, and this was correlated with improved PPI. The data suggest that responses of IC neurons reflect both hearing loss-induced plasticity and changes induced by exposure to an AAE, and these neural changes are correlated with the magnitude of PPI.

Moderate noise trauma in juvenile cats results in profound cortical topographic map changes in adulthood.

Cortical topographic map changes have been reported after profound drug-induced hearing loss in neonates, after progressive high-frequency hearing loss, and after mechanically induced lesions in the cochlea of adult animals. The present study demonstrates that exposure of 5-week-old kittens to a loud 6 kHz tone, producing mild to moderate high-frequency hearing loss, induces a profound reorganization of the frequency map in auditory cortex. In the reorganized cortical region, the frequency-tuning curves were of normal sharpness with near normal thresholds. Inhibitory tuning curve bandwidths were similar to those in control animals. Spontaneous activity in the reorganized part of the cortex was significantly increased. In contrast, the strength of the cross-correlation of the spontaneous activity of units recorded on different electrodes was the same in the normal and reorganized part. Minimum first-spike latency was significantly increased in trauma cats, largely for units at the dorsal side of the sampled region. Because most other neural response properties are normal in the reorganized part of cortex, sub-cortical topographic map changes are likely involved in producing the altered cortical topographic maps.

The BALB/c mouse as an animal model for progressive sensorineural hearing loss

To develop the BALB/c mouse strain as an animal model for the study of progressive sensorineural hearing loss, mice ranging in age from young adult through middle age were studied. Auditory brainstem response thresholds, histopathology [cytocochleograms for hair cells, the packing density of spiral ganglion cells (SGCs), the number of neurons and overall size of the anterior ventral cochlear nucleus (AVCN)], and behavioral paradigms (prepulse inhibition, fear-potentiated startle) were compared with previous data from C57BL/6J (C57) and DBA/2J (DBA) mouse strains. Progressive high frequency hearing loss in BALB/c mice was generally more rapid than C57 and slower than DBA (e.g. mean thresholds for 16 kHz: 10-month-old BALB/c mice=71 dB SPL; 55-day-old DBA mice=79 dB SPL; 12-month-old C57 mice=50 dB SPL). Like the other strains, BALB/c exhibited a progressive loss of hair cells and SGCs that was most severe in the cochlear base and least severe in the middle turns; however, BALB/c mice had relatively more SGC loss in the apex. Unlike C57 and DBA, no loss of neurons was observed in the AVCN following cochlear pathology (although AVCN volume was reduced). Like the other strains, successful fear conditioning was obtained with a 12 kHz conditioned stimulus. Prepulse inhibition showed that middle and low frequency tones (4–12 kHz) became more salient as high frequency hearing declined. Similar results had been previously obtained with C57 and DBA mice and were interpreted as reflecting hearing-loss-induced plasticity in the central auditory system.

Ear and hearing problems in 44 middle-aged women with Turner's syndrome

The present study has investigated ear and hearing problems in 44 women with Turner's syndrome (median age 45.5 years). Social hearing problems were common after the age of 40 and 27% were fitted with hearing aids. Audiograms revealed a hearing loss > 20 dB hearing level (HL) in 91% leading to clinically significant hearing problems in 60%. A distinct dip in the 1.5 kHz frequency range, with a mean value of 46 dB was found in 30 women. The occurrence of the dip was correlated to the karyotype. All women with the karyotype 45,X and 45,X/46,X,i(Xq) demonstrated this dip while in the 45,X/46,XX group it was found in 31%. No dips were found among 45,X/46,XY and 45,X/46,XX/47,XXX women. With increasing age a progressive high frequency hearing loss was added to the dip leading to severe hearing problems earlier in the Turner women than age-matched controls. This might be due to a genetic defect leading to premature ageing of their hearing organ. These data emphasize the importance of providing early information to Turner girls of their predisposition to hearing impairment. Patient awareness of importance of audiological evaluations and the benefit of hearing aids should be stressed.