The relationship between electrolyte balance and cochlear disturbances in cases of renal failure

The multifaceted links between hearing loss and chronic kidney disease

Hearing loss affects nearly 1.6 billion people and is the third-leading cause of disability worldwide. Chronic kidney disease (CKD) is also a common condition that is associated with adverse clinical outcomes and high health-care costs. From a developmental perspective, the structures responsible for hearing have a common morphogenetic origin with the kidney, and genetic abnormalities that cause familial forms of hearing loss can also lead to kidney disease. On a cellular level, normal kidney and cochlea function both depend on cilial activities at the apical surface, and kidney tubular cells and sensory epithelial cells of the inner ear use similar transport mechanisms to modify luminal fluid. The two organs also share the same collagen IV basement membrane network. Thus, strong developmental and physiological links exist between hearing and kidney function. These theoretical considerations are supported by epidemiological data demonstrating that CKD is associated with a graded and independent excess risk of sensorineural hearing loss. In addition to developmental and physiological links between kidney and cochlear function, hearing loss in patients with CKD may be driven by specific medications or treatments, including haemodialysis. The associations between these two common conditions are not commonly appreciated, yet have important implications for research and clinical practice.

Investigating Hearing Function in Pediatric Patients with Renal Dysfunction: In Pursuit of Preventive Audiology Outcomes

Chronic kidney is being increasingly recognized as a global health problem with effects that have implications for both mortality and morbidity; with hearing loss being one of the effects that has an impact on quality of life. This study aimed to describe hearing function in a group of children with chronic renal dysfunction receiving treatment in an academic hospital in Johannesburg, South Africa. One hundred children between the ages 5 and 18 years (mean age 11.68) were included in the study. A cross-sectional, descriptive, quantitative research design was employed. All participants underwent a case history interview and an audiological examination which included otoscopy, immittance testing, pure tone audiometry including extended high frequency testing up to 16 kHz as well as diagnostic distortion product otoacoustic emission testing. A medical record review was also done. Both descriptive and inferential statistics were used to analyze the collected data. Results revealed that there was a high prevalence of hearing loss in this group. The most common hearing loss was a low and high to ultrahigh frequency mild sensorineural hearing loss. No relationship between the severity of hearing loss and the severity of renal dysfunction, or the duration of renal dysfunction and the duration of treatment was found. However, a relationship between the severity of hearing loss and certain treatments was found. These were v hemodialysis and the use of ototoxic medication such as loop diuretics, tuberculosis medication, and antimalarial medication. Current findings highlight the importance of extended high frequency audiometry as well as diagnostic distortion product otoacoustic emission testing for early detection of hearing impairment, in pursuit of preventive audiology outcomes, in ototoxic monitoring in this population.

The association between reduced kidney function and hearing loss: a cross-sectional study

Background

The relationship between kidney function and hearing loss has long been recognized, but evidence of this association mostly comes from small observational studies or other populations. The aim of this study is to explore the association between reduced kidney function and hearing loss in a large population-based study among the middle-aged and elderly Chinese.

Methods

Data collected from the Chinese Health and Retirement Longitudinal Study (CHARLS) in 2015 were used for analysis. A cross-sectional study was conducted among 12,508 participants aged 45 years and older. Hearing loss, the outcome of this study, was defined according to interviewees’ responses to three survey questions related to hearing in the CHARLS. Estimated glomerular filtration rate (eGFR) was employed to assess kidney function, and participants were classified into three categories based on eGFR: ≥90, 60–89 and < 60 mL/min/1.73 m². Multivariable logistic regression was employed to adjust for potential confounders, including demographics, health-related behaviors, and cardiovascular risk factors.

Results

The overall prevalence of self-reported hearing loss in the study population was 23.6%. Compared with participants with eGFR ≥90 mL/min/1.73 m², participants with eGFR of 60–89 mL/min/1.73 m² (odds ratio [OR]: 1.11, 95% confidence interval [CI]: 1.00–1.23) and eGFR < 60 mL/min/1.73 m² (OR: 1.25, 95% CI: 1.04–1.49) showed increased risk of hearing loss after adjusting for potential confounders.

Conclusions

Reduced kidney function is independently associated with hearing loss. Testing for hearing should be included in the integrated management of patients with chronic kidney disease.

Audiovestibular functions in chronic kidney disease in relation to haemodialysis

Background

Several studies have reported that the audiovestibular system is affected in patients with chronic kidney disease.

Objective

This study aimed to investigate how the audiovestibular system is affected in patients with various stages of chronic kidney disease.

Methods

Sixty participants were divided into three groups: group 1 – controls; group 2 – chronic kidney disease patients receiving conservative treatment; and group 3 – chronic kidney disease patients undergoing regular haemodialysis. Assessments included: standard and high-frequency audiometry and otoacoustic emissions testing, oculomotor tests, and combined vestibular-evoked myogenic potentials testing.

Results

Fifty per cent of group 2 and 60 per cent of group 3 had bilateral sensorineural hearing loss. High-frequency pure tone audiometry showed reduced detectability and higher thresholds at 12 kHz and 16 kHz in patients than in controls. Otoacoustic emissions, tracking, optokinetic and combined vestibular-evoked myogenic potential tests showed abnormal results in chronic kidney disease cases.

Conclusion

Both the auditory and vestibular pathways are affected in different stages of chronic kidney disease. High-frequency pure tone audiometry, otoacoustic emissions and combined vestibular-evoked myogenic potentials could be performed routinely in patients with chronic kidney disease, regardless of the disease stage.

Cochlear implantation in a patient with combined renal and liver transplantation

OBJECTIVE AND IMPORTANCE

Patients who have undergone solid organ transplantation and continuing immunosuppressant medication are at a higher risk of wound problems and infections following cochlear implantation. This risk is theoretically even further increased in multi-organ transplant recipients due to the increased doses of immunosuppressive medications that these patients are administered.

CLINICAL PRESENTATION AND INTERVENTION

Here, we present the first reported case of successful cochlear implantation in a patient who had previously undergone successful combined liver and kidney transplant. She had no significant complications from the surgery and had good audiological outcomes 3 months post-operatively.

CONCLUSION

As we continue our advances in the use of cochlear implant technology, our report adds to the growing evidence of its benefits in transplant recipients. However, there are important pre- and peri-operative considerations in this group of patients which can improve safety and outcome.

Achados audiológicos em pacientes submetidos ao transplante renal

OBJETIVO: Investigar o comportamento auditivo de pacientes com insuficiência renal crônica submetidos ao transplante renal. MÉTODOS: Foram avaliados 30 pacientes, 10 do gênero feminino e 20 do gênero masculino, na faixa etária de 13 a 26 anos (média de idade 16,97 anos). Os sujeitos foram submetidos a anamnese, avaliação otorrinolaringológica, avaliação audiológica convencional e de altas frequências, medidas de imitância acústica e avaliação do processamento auditivo central. Para os resultados da audiometria de altas frequências foi utilizado um grupo controle. RESULTADOS: Os sujeitos não apresentaram queixas auditivas na anamnese. Os resultados da audiometria convencional demonstraram predomínio da normalidade; na audiometria de altas frequências, os pacientes apresentaram resultados piores do que os sujeitos do grupo controle. Na imitanciometria houve predomínio de curva tipo A bilateral. Na avaliação do processamento auditivo central, 14 sujeitos (46,67%) apresentaram resultados alterados no Staggered Spondaic Word Test (SSW). Houve diferença significativa entre a variável idade e o resultado da audiometria tonal limiar: quanto maior a idade, menor a sensibilidade auditiva nos limiares de 250 Hz a 8 kHz. Houve relação entre o tipo de doador (cadáver ou vivo) e o resultado do teste SSW: os índices de resultados alterados foram maiores quando o doador era cadáver, em comparação com casos de doador vivo. CONCLUSÃO: Houve alterações na avaliação audiológica convencional e de altas frequências e no processamento auditivo central de sujeitos com insuficiência renal crônica submetidos ao transplante renal, sugerindo a necessidade de orientação à equipe envolvida quanto aos cuidados, prevenção e identificação precoce de acometimentos audiológicos.

Hearing loss in patients of chronic renal failure: a study of 100 cases

The purpose of our study was to determine the incidence of hearing loss and to describe the hearing impairment and the possible contributing factors, responsible for sensori neural hearing loss in chronic renal failure (CRF) patients. This was a prospective study carried out on 50 cases of CRF attending otorhinolaryngological services for hearing disturbance and on 50 healthy volunteers for control study, having the same inclusion criteria except (does not suffering with CRF) having normal renal function tests. These volunteers attended the ENT OPD, for oto-rhino-laryngological services but not for hearing problems. 14 (28%) out of 50 cases of CRF had sensori neural hearing loss of moderate to severe degree in the high frequency range which was bilateral and symmetrical, while in control group the incidence of sensorineural hearing loss was only 6%.

Severe to profound hearing loss in patients with progressed Alport's syndrome

CONCLUSION

The concept of hearing loss severity must be redefined, as there is a clear need for more active hearing management in Alport's syndrome patients with severe and profound hearing loss.

OBJECTIVES

Sensorineural hearing loss (SNHL) caused by Alport's syndrome generally does not exceed 60-70 dB, because a cochlear lesion is responsible for this hearing loss. Careful management of renal function improves the prognosis and the longevity of Alport's syndrome patients; it is useful to reassess SNHL caused by Alport's syndrome.

PATIENTS AND METHODS

Thirty-two patients with Alport's syndrome were analyzed retrospectively. Pure tone audiograms (PTAs), speech audiograms, and transiently evoked otoacoustic emissions (TEOAEs) were performed. Hearing loss severity was compared to duration of disease and severity of renal dysfunction. We also evaluated the correlation between OAEs and PTAs according to the hypothesis that evoked OAEs would be abnormal even in early stage SNHL in Alport's syndrome.

RESULTS

The level of hearing was positively correlated with disease duration. The hearing of the end-stage renal disease (ESRD) group, whose hearing threshold could exceed 70 dB, was worse than that of the non-ESRD group. OAEs were found in patients with normal hearing and mild hearing loss and had no significant early detection value.

The hearing status in 12 female and 15 male Japanese Fabry patients

OBJECTIVE

Fabry disease (FD) is an x-linked inherited disease that causes a lack of a lysosomal enzyme, alpha-galactosidaseA, leading to cellular accumulation of glycosphingolipids of the whole body. This accumulation in the inner ear causes hearing loss also. However, FD is rare, and the frequency is lower in females than in males. Thus, there have been few comparative studies between women and men for hearing loss in FD. Accordingly, we examined the hearing status of both male and female FD patients and elucidated the similarities and differences. We also analyzed for correlations between the hearing status and renal and heart disorders.

METHODS

12 women and 15 men were studied by means of pure tone audiometry, the relationships between the hearing status and the renal and cardiac functions.

RESULTS

The audiogram type was the flat type in a majority of both women and men, followed by the high type and low type, while the U-shaped type was rare. Examination of the thresholds average showed abnormality in one woman and four men. Comparison to threshold for each age bracket of normal subjects showed abnormality in three women and nine men. No correlations were found between the hearing loss and either the renal or cardiac function. All the patients with renal dysfunction had abnormal hearing.

CONCLUSIONS

The frequency of hearing loss in FD was higher in men than in women. Also, there may be some relationship between renal function and hearing loss in FD.

Cochlear Function in Chronic Kidney Disease and Renal Transplantation: A Longitudinal Study

Hearing loss on pure-tone and brainstem-evoked response audiometry is well documented in chronic kidney disease patients, but there are only scant data in renal allograft recipients. The aim of this study was to evaluate cochlear function on pure-tone and brainstem-evoked response audiometry among patients of chronic kidney disease to document changes after renal transplantation. The study included 20 healthy controls and 40 patients: 10 each at stage 3 and 4 and 20 with stage 5 chronic kidney disease. Patients with known causes for hearing loss were not included. Patients with stage 5 chronic kidney disease were reevaluated 1 year after renal transplantation. Compared with healthy controls, chronic kidney disease patients showed a highly significant bilateral sensorineural hearing loss at all frequencies of 0.25 to 8.0 kHz, which was more marked in higher frequencies. A highly significant delay in the latencies of waves I, III, and V and interpeak latencies of I to III and I to V was also noted on brainstem-evoked response audiometry. Compared with their pretransplant values, there was a significant improvement in the delay in absolute latencies of I, III, and V among renal allograft recipients. There was no correlation of audiometry findings with gender, degree of renal failure, and serum sodium. Hearing loss was seen in 70% of stage 3 and 4 chronic kidney disease and 60% in stage 5. The intensity of hearing loss was variable. In conclusion, chronic kidney disease patients shows definitive audiologic dysfunction with some improvement in hearing and wave latencies after successful renal transplantation.

Potential Ototoxicity of Aluminum in Hemodialysis Patients

OBJECTIVES/HYPOTHESIS

Aluminum (Al) is a neurotoxin in both human and animal models. Al accumulation is usually observed in patients with end-stage renal disease (ESRD). To clarify whether Al also exhibits toxic effects on the specified neural organ of inner ear, we recruited hemodialysis (HD) patients to investigate the effect of serum Al level on the auditory physiology.

STUDY DESIGN

Forty patients in maintenance HD as well as 40 age-matched healthy subjects without hearing complaints were enrolled. The auditory function tests, including pure-tone audiometry (PTA), distortion-product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR) were performed in all subjects. The serum Al levels determined within 3 months of auditory tests were used for analysis.

RESULTS

High-frequency hearing impairment was the predominant auditory dysfunction in HD patients who showed worse high-tone hearing level on PTA and diminished amplitudes of DPOAEs at 3 K and 4 K as compared with the controls (P < .001). Age was a significant factor determining the auditory dysfunction in both HD patients and control subjects. After age correction, serum Al level correlated reversely with the amplitude of DPOAEs-2 K (P = .002), but not with amplitudes of DPOAEs-3 K, -4 K, hearing levels on PTA, or wave latencies on ABR.

CONCLUSION

High-frequency hearing impairment is a common presentation in HD patients. Serum Al level correlates reversely with the amplitude of DPOAEs-2 K but not those of DPOAEs-3 K, -4 K, hearing levels on PTA, and wave latencies on ABR. Possibly, the correlation between the Al level and the high-frequency OAE results was obscured by the significantly diminished amplitudes of DPOAEs-3 K, -4 K in ESRD patients. These results implicate that the effect of Al is mainly of cochlear origin rather than of retrocochlear origin.

Effects of a single session of hemodialysis on hearing abilities

A prospective study was designed to evaluate the effects of a single session of hemodialysis on the parameters of hearing. We carried out serial audiological tests (tympanometry, pure-tone, speech and high frequency audiometry) in 19 patients with chronic renal failure undergoing hemodialysis. Tests were performed on patients 1 h before and 2 and 24 h after a randomly selected session of hemodialysis. The results of audiological tests indicated no significant adverse effect of a single session of hemodialysis on hearing.

A study of otorhinolaryngological manifestations in patients of chronic renal failure

The present study was carried out on 50 patients of Chronic renal failure (CRF), Majority of CRF patients had high frequency hearing loss, but inner ear changes were found to be irreversible even after dialysis. All cases had cochlear lesion. No relationship could be established between the level of blood urea, creatinine, serum potassium, serum calcium and blood pressure with the severity of the impaired hearing. A direct correlation was seen between increasing hyponatraemia and impaired hearing. No direct relationship could be made between blood pressure and epistaxis, but all the cases had raised blood urea.

Expression of basement membrane type IV collagen chains during postnatal development in the murine cochlea

An immunofluorescence study was performed to examine the temporal and spatial patterns of expression for the different type IV collagen chains during postnatal cochlear development. At birth, the classical chains (4A1 and 4A2) were widely expressed, while the novel chains (4A3, 4A4, and 4A5) were completely absent. Activation of the novel chains was observed at 4 days of age, with intense, widely distributed immunostaining suggesting that most of the cells in the cochlea express the novel chains at this developmental stage. From day 8 through day 14, developmental inactivation of the novel chains results in a reduction of generalized immunoreactivity with a concomitant elevation of specific staining in the membranous structures bounding the interdental cells of the spiral limbus, the inner sulcus, the basilar membrane, and in a fibrous bed of staining radiating from the spiral prominence into the region of the spiral ligament which corresponds to the location of the root cell processes. This pattern of intense immunostaining for the novel chains persists through adulthood. The classical chains are expressed in these same anatomical regions only transiently (from day 6 to day 10), after which a gradual developmental inactivation leads to the adult expression pattern where classical collagen chains are found primarily in the perineurium, in the membranes surrounding the spiral ganglion cell bodies, and in the vascular basement membranes of the spiral ligament and the stria vascularis. The complex developmental pattern of expression for the type IV collagen chains in the murine cochlea is similar to that observed in the murine kidney, which is the other major site for basement membrane pathology in Alport syndrome.

Sensorineural hearing loss in patients reaching chronic renal failure in childhood

The incidence of sensorineural hearing loss (SNHL) was investigated in 68 patients who reached chronic renal failure (CRF) in childhood with the aim of identifying possible risk factors. Tests were carried out by means of pure-tone and impedance audiometry. SNHL was found in 29% of patients on conservative treatment, 28% of patients on hemodialysis, and 47% after renal transplantation. Differences among groups were not significant. A significant correlation was found with the administration of ototoxic drugs (aminoglycosides and furosemide). We hypothesize that SNHL may be reduced in patients with CRF or on renal replacement therapy by strictly monitoring ototoxic therapy.

The hearing of the patients treated with hemodialysis: a long term follow-up study

Sensorineural hearing loss is frequently found in the patients under the treatment with hemodialysis, but the responsible etiological factor(s) still remains controversial. The purpose of the present study was to determine by a long term follow-up study whether hemodialysis per se or other factors induce sensorineural hearing loss. Thirty-seven patients with the observation periods of 4 years or longer were selected for the analysis. Hearing tests were performed soon after the initiation of hemodialysis and every 3 to 12 months thereafter. Significant hearing loss was found in 16 cases (31 ears) at the first test. Although 3 cases (5 ears) of the initially normal group and one case (2 ears) of the group with already existing hearing loss exhibited significant hearing loss, the change in the hearing level was quite minimal in remaining 67 ears during the observation period. Although the cochlea in patients under the treatment with hemodialysis is susceptible to various insults, we conclude that hemodialysis per se does no harm to the cochlea and the hearing can be maintained at the pre-hemodialysis level in the majority of the cases.

Hearing Loss in Chronic Renal Failure-Hearing Threshold Changes following Haemodialysis

The prevalence of sensorineural hearing loss, measured by pure tone audiometry, was determined in 66 patients with chronic renal failure and threshold changes following haemodialysis were measured in 31 patients.

The incidence of hearing loss was 41% in the low, 15% in the middle and 53% in the high frequency ranges respectively. No correlations with weight changes, haematocrit, metabolic bone disease or ototoxic drug history were found.

Of 62 ears studied, 38% had a decrease in low frequency threshold after dialysis and 9% had an increase. Threshold in 22/31 ears with pre-existing low frequency loss altered after dialysis with little change in other frequencies and no correlation with weight changes.

In conclusion, we find a high incidence of low and high frequency hearing losses in chronic renal failure patients. Fluctuation in low frequencies with dialysis is common. Possible mechanisms include treatment induced changes in fluid and electrolyte composition of endolymph.

Effects of renal insufficiency on the cochlear absorptive-secretory areas. A morphological study in the Mongolian gerbil

In order to evaluate the effects of experimental renal insufficiency (RI) on the labyrinthine absorptive-secretory areas (ASA), 54 adult Mongolian gerbils were submitted to bilateral nephrectomy or to sham procedure. At different intervals (3, 6, 9, 12, 15, 18, 21, 24 hours) after the surgical procedures, or during the terminal stage (28 h) the animals were decapitated and both temporal bones were dissected to obtain selected specimens of the cochlear ASA. The specimens were processed and analysed by light and electron microscopy. Structurally, RI induced progressive thickening of the epithelial components (stria, prominentia, sulcus); separation by fluid accumulation between stria and mesodermal layer; and frequent dilatation of intraepithelial vessels. Ultrastructurally, diverse signs were observed parallel to the evolution of the RI. After 12 h a progressive enlargement of the intercellular spaces, which was particularly evident in the stria surrounding the vessels and in the other sulcus, was observed. Its latest expression was a marked widening of the basolateral spaces containing a granular substance. After 12 h the formation of large cytoplasmic perinuclear spaces containing small rounded vesicles, probably secondary to fluid accumulation, could be observed in the marginal cells. After 24 h diverse signs of organellar damage became evident (schedule: mitochondrial swelling, lysosome like figures, myelin like figures). In the terminal stage, a general homogenization of the cytosol was common. The findings suggest a definite re-distribution of fluids in the inner ear. A close relationship between renal dysfunction and labyrinthine microhomeostasis is therefore proposed.

Audiological findings in elderly patients with chronic renal failure

The audiological results of 46 patients (m/f 27/19, mean age; 57.4 +/- 11.1) with chronic renal failure (CRF) undergoing dialysis were compared with those of an age- and gender-matched control group (n = 25). Mean pure tone average from 0.5 to 8 kHz was about 15 dB higher in CRF patients than in control subjects. The ABR parameters of the test group were then contrasted with those recorded in a second control group (n = 47, m/f 26/21, mean age: 56.1 +/- 11.4) matched by age, gender and degree of hearing loss (HL). After assessing the normality of the groups by the usual criteria, using the data of a sample of normal young adults, the ABR were found to be abnormal in 23.9% of the controls and in the 39.13% of the CRF patients. Wave V, I-III, III-V and I-V delays were significantly shorter in the females of the control group; in the CRF group, only the V and the I-V delays were shorter in females. The only age-dependent effect was found in the CRF sample, in which older patients had significantly longer I-III IPLD. The degree of HL influenced the latency of the waves in both groups but only the I-V IPLD was longer in CRF patients with pronounced high tone loss. The most distinguishing feature between the effects of CRF plus ageing and those of normal ageing was the lengthening of the I-III IPLD in the test group. This finding is likely to reflect a subclinical disorder of the VIII nerve function that is a part of the axonal uremic neuropathy.

A new syndrome: hearing loss and familial salivary gland insensitivity to aldosterone in two brothers

Two male siblings presented in infancy with hyponatremia. The levels of plasma renin activity and aldosterone were elevated. Sodium supplement was necessary to maintain normal sodium balance. The salivary sodium concentrations were markedly elevated, with sweat sodium levels being in the upper normal range. Urinary sodium concentration and renal epithelial exchange between sodium and potassium were normal. This was felt to be due to an autosomal recessive disorder. Both siblings were later diagnosed as having a bilateral moderate to severe sensorineural hearing loss with intermittent conductive overlay due to middle ear fluid. The sensorineural loss was also felt to be autosomal recessive in origin, but the possibility of a disturbance of sodium balance in the inner ear has been questioned.

Auditory brain-stem evoked potentials in patients undergoing dialysis

Auditory brain-stem evoked potentials (ABEPs) and pure-tone audiograms were obtained for 38 patients with renal failure, undergoing dialysis, before and after a dialysis session, and for 40 healthy normal subjects. Blood chemistry was also evaluated for each patient before and after dialysis. ABEP abnormality (using 10/sec click rate) was observed for 24% of the patients, rising to 44% when 55/sec measures were included. Abnormalities included prolongations of peak latencies for both click rates, and prolongation of interpeak latency differences. Pre-dialysis calcium was significantly different between patients with or without ABEP abnormality. In addition to this chronic effect on ABEPs, an acute effect of the dialysis session was found. Blood chemistry data, ABEP latencies and I-III interpeak latency differences were significantly different before, as compared to after dialysis. The acute effect of dialysis on blood calcium levels correlated with its effect on latencies of peaks III and V at 10/sec click rate, and on peaks I and V latency at 55/sec. These results may indicate the types of dysfunction revealed by increased stimulus rate measures.

Hearing loss in end-stage renal disease - effect of dialysis

Hearing sensitivity was determined in 23 patients with end-stage renal disease shortly before and 1-5 years after the institution of maintenance hemodialysis. Normal or only slightly abnormal hearing sensitivity was found in 9 of our 23 patients while the remaining 14 patients had marked hearing abnormalities at the onset of dialysis treatment. Neither group showed any significant change in their audiographic findings during the study period. It thus appears that chronic hemodialysis may have no effect on hearing abnormalities associated with end-stage renal disease.

Hearing loss in patients with dialysis and renal transplants

Hearing loss in renal dialysis and renal transplant patients occurs quite frequently. An assessment of the likely etiological factors is nearly impossible in a retrospective analysis of any one patient because many factors exist simultaneously. In a prospective study of a large series of patients an identification of factors contributing to the hearing loss was possible in the majority of patients. During the study it became increasingly apparent that what was observed at any one time was the combined effect of many factors. Although one factor seemed to precipitate the hearing loss it was inadvisable to attribute total responsibility to that agent or circumstance. Further, this combined effect was not a simple addition of effects but potentiation. The serious implications of this phenomenon are discussed.

[Ultrastructural changes of the stria vaseularis and the spiral ligament in chronic uremic rats (author's transl)]

Looking for the morphological correlation of uremic inner ear damage a 5/6 resection of kidney parenchyma in rats was performed. A biochemically proven chronic uremia was so created. The ultrastructural examination of the stria vascularis showed a marked swelling of the intermediate cells, compressing occasionally stria vessels. The stria was enlarged and the mitochondria of the dark and light cells swollen. In the spiral ligament connective tissue cells were moderately swollen and blood vessels partially obstructed by swelling of the endothelium. These changes are proved not to be dependent on the urea. The pathophysiological significance for uremic inner ear damage can only be determined after further examination of cochlear tissue.

Hearing function and chronic renal failure

In order to evaluate the degree and type of hearing loss in patients with chronic renal failure, 61 patients undergoing chronic hemodialysis were examined. Hearing threshold levels, adjusted for age and sex, demonstrated a significant high frequency deficit, which in some patients was noted early in the course of hemodialysis. Fluctuations in hearing were noted over single dialysis events but were transient and apparently independent of corresponding changes in Na, K, Ca, BUN, creatinine, glucose, mean blood pressure, and weight. Preliminary attempts to evaluate hyperlipidemia as a possible cause of hearing loss did not reveal any hearing deficit or gain as related to triglyceride or cholesterol levels. The data suggested other possible causes of observed auditory loss.

Hearing loss in renal disease: clinical and pathological studies

Ninety-one of 224 chronic renal patients, most of them hemodialysis and/or transplant patients, had sensorineural loss: 11% noise exposure; 7% genetic; 22% due to multiple factors, including ototoxicity; 41% with hearing loss and ototoxic drug exposure, (but one-fourth had had insufficient drugs to cause hearing loss) and 11% were of unknown etiology. Hearing loss and normal hearing patients exposed to ototoxicity or multiple factors were similar in all parameters but hearing loss. Ten temporal bone cases are described, two from patients with hearing loss of unknown origin. One showed cochlear hydrops, fibrous tissue proliferation in cochlear perilymphatic spaces, Corti's organ degeneration, displaced tectorial membrane and probable metastatic calcification in the stria vascularis. The other case showed hair cell loss. Three patients had had ototoxic drugs; one bad hair cell loss and tectorial membrane abnormalities; one had hair cell loss and metastatic strial calcification; one was normal. One patient had pus in both internal auditory canals. Another bad otosclerotic focus without stapes fixation. Three were normal. We do not yet recognize pathology typical of hearing loss of severe renal disease. Findings seem to fall into two broad categories: those of known entities and those of obscure etiology.