Delayed auditory brainstem responses in diabetes mellitus

Changes in the cochlear and retrocochlear parts of the auditory system in 19-39 and 40-60 years old patients with type 1 diabetes mellitus

Pathophysiological alterations in the cochlea and functional tests of the auditory pathway support that in diabetes both vasculopathy and neural changes could be present. The aim of our research was to study the differential effect of type 1 diabetes mellitus (T1DM) on two different age groups. Audiological investigation was carried out in 42 patients and 25 controls at the same age groups. Investigation of the conductive and sensorineural part of the hearing system by pure tone audiometry, distortion product otoacoustic emission measurement and acoustically evoked brainstem response registration were evaluated. Among the 19-39-year-old people the incidence of hearing impairment was not different in the diabetes and control groups. Among the 40-60-year-old people hearing impairment was more common in the diabetes group (75%) than in the control group (15,4%). Among patients with type 1 diabetes, the mean threshold values were higher in both age groups at all frequencies although significant difference was in 19-39 years old group: 500-4000Hz right ear, 4000Hz left ear, in 40-60 years old group: 4000-8000 Hz both ears. In the 19-39 years old diabetes group only at 8000 Hertz on the left side was a significant (p<0,05) difference in otoacoustic emissions. In the 40-60 years old diabetes group significantly less otoacoustic emissions at 8000 Hz on the right side (p<0,01) and at 4000-6000-8000 Hertz on the left side, (p<0,05, p<0,01, p<0,05 respectively) was present compared to the control group. According to ABR (auditory brainstem response) latencies and wave morphologies, a possible retrocochlear lesion arose in 15% of the 19-39 years old and 25% of the 40-60 years old diabetes group. According to our results, T1DM affects negatively the cochlear function and the neural part of the hearing system. The alterations are more and more detectable with aging.

Auditory Late Latency Response in Individuals with Type 2 Diabetes Mellitus

OBJECTIVES

The study was done to compare Auditory late latency response (ALLR) in normal-hearing individuals without diabetes mellitus and normal-hearing individuals with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

A total of 50 participants within the age range of 40-60 years were enrolled in the study based on the inclusion and exclusion criteria. They were divided into two groups with one group consisting of 25 individuals with T2DM and the other group consisted of 25 individuals without diabetes as the control group.

RESULTS

The results revealed prolonged latencies and reduced amplitude of P1, N1 and P2 wave among individuals with T2DM compared to control group. There was a significant positive correlation observed for ALLR latency and duration of T2DM, and a negative correlation observed for ALLR amplitude and duration of T2DM.

CONCLUSION

The present study concluded that there is a problem in the encoding of speech at the cortical level despite normal hearing in individuals with type 2 diabetes mellitus.

Hearing loss in type 1 diabetes: Are we facing another microvascular disease? A meta-analysis

OBJECTIVE

Evidence shows type 1 diabetes(T1D) leads to vascular damage and neuropathy. The purpose of this study was to perform a systematic review and a meta-analysis to assess the evidence of the effects of T1D on hearing function.

METHODS

Three electronic databases were used. The articles were independently reviewed by two authors using predefined inclusion criteria to identify eligible studies. They were then classified as high or low methodological quality. Meta-analysis was performed on pooled data of hearing loss(HL) prevalence, pure tone audiometry(PTA), otoacoustic emissions(OAE) and auditory brainstem response(ABR).

RESULTS

Twenty-one articles fulfilled the inclusion criteria. In all studies, HL was defined as pure tone greater than 20 dB in at least one frequency. The prevalence of HL ranged between 5.17% and 48% for diabetics, which was higher than in controls which ranged between 0% à 40% (OR = 7.7, 95% CI 3.32-17.98, p < 0.05 and I² = 40%). The tendency of mean thresholds of PTA was higher in diabetics than in controls, with results being statistically significant at 250, 500 and 1000 Hz. OAE were significantly lower in diabetic patients. ABR latencies were longer in T1D group compared to controls and were statistical significant.

CONCLUSIONS

Patients with T1D have a significantly greater prevalence of HL compared to the control group. These damages could be compared to other microvascular diseases. Further studies are needed to assess whether hearing testing should be considered as a part of the screening process in T1D patients and therefore, secondary preventive treatment may be warranted as well.

Delayed auditory conduction in diabetes: is metformin-induced vitamin B12 deficiency responsible?

The present study aims to evaluate the functional integrity of the auditory pathway in patients with diabetes taking metformin. A further aim is to assess its association with vitamin B12 deficiency induced by metformin. Thirty diabetics taking metformin and 30 age-matched non-diabetic controls were enrolled. Stimulus-related potentials and vitamin B12 levels were evaluated in all the subjects. The diabetics showed deficient vitamin B12 levels and delayed wave III latency and III-V interpeak latency in the right ear and delayed Na and Pa wave latencies in the left ear compared with the controls. The dose and duration of metformin showed no association with the stimulusrelated potentials. Therefore, although vitamin B12 levels were deficient and auditory conduction impairment was present in the diabetics on metformin, this impairment cannot be attributed to the vitamin B12 deficiency.

Auditory Impairment in Young Type 1 Diabetics

BACKGROUND AND AIMS

More attention has recently been focused on auditory impairment of young type 1 diabetics. This study aimed to evaluate auditory function of young type 1 diabetics and the correlation between clinical indexes and hearing impairment.

METHODS

We evaluated the auditory function of 50 type 1 diabetics and 50 healthy subjects. Clinical indexes were measured along with analyzing their relation of auditory function.

RESULTS

Type 1 diabetic patients demonstrated a deficit with elevated thresholds at right ear and left ear when compared to healthy controls (p <0.01). The elevated auditory threshold was significantly related with HDL-cholesterol, diabetes duration, and systemic blood pressure (p <0.05). Moreover, latencies of right ear (wave III, V and interwave I-V) and left ear (wave III, V and interwave I-III, I-V) in diabetic group significantly increased compared to those in control subjects (p <0.01). Auditory brainstem response was significantly related with GHbA1C and microalbuminuria (p <0.01). Furthermore, distortion product evoked otoacoustic emissions (DPOAE) of diabetes group were statistically significant in right ears at 4.0, 6.0 kHz and in left ears at 4.0, 6.0, 8.0 kHz (p <0.01) compared with those of controls. Diabetic patients demonstrated lower amplitude responses of the right ear than the left ear at 8.0 kHz. Only triglyceride was positively correlated to the hearing impairment defined by DPOAE (p <0.01). There was no significance of transient evoked otoacoustic emissions (TEOAE) between groups. TEOAE was associated with age and GHbA1C (p <0.01).

CONCLUSIONS

Type 1 diabetics exerted higher auditory threshold, slower auditory conduction time and cochlear impairment. HDL-cholesterol, diabetes duration, systemic blood pressure, microalbuminuria, GHbA1C, triglyceride, and age may affect the auditory function of type 1 diabetics.

Cardiovascular risk factors as causes for hearing impairment

The purpose of this paper is to provide a contemporary review of the correlation between cardiovascular risk factors (CVRFs) and hearing impairment (HI) . We conducted a comprehensive review of the literature in order to assess the effects of the different CVRFs on HI. We focused on the pathological findings in the inner ear and their correlation with cochlear function in population-based studies. We found that CVRFs adversely affect hearing acuity. HI diagnosis should be accompanied by detecting and treating CVRFs, according to the presented outline, which may augment hearing rehabilitation and improve the general health and the well-being of the patient. © 2014 S. Karger AG, Basel.

Is type 1 diabetes mellitus a cause for subtle hearing loss in pediatric patients?

The objective of this study is to investigate the effects of IDDM on the function of the auditory pathway from the cochlea to the auditory cortex in child patients. Totally, 140 ears of 70 children with IDDM and 60 ears of 30 age and gender-matched healthy controls were included in the study. The ages of patients and controls ranged from 4 to 14 years. Audiological assessment including pure-tone audiometry, otoacoustic emission testing (OAE) and auditory brainstem response testing (ABR) has been performed to all participants. There was no significant difference between the patients and controls regarding pure-tone thresholds on audiometry (p > 0.05). The latencies of waves I, III and V on ABR were not significantly different between the patients and controls (p > 0.05). The amplitudes on DPOAE testing obtained from both groups were not significantly different at the frequencies of 2,000 and 4,000 Hz (p > 0.05). However, the DPOAE amplitudes of the patients at 1,000 Hz were significantly lower than those of controls at the same frequency (p = 0.03). There was no difference between the patients who had chronic disease (>5 years) and healthy controls regarding pure-tone audiometry, ABR and DPOAE testing results (p > 0.05). In the light of the findings obtained with pure-tone audiometry, and OAE and ABR testing, it seems that auditory system is spared in children with IDDM at clinical level. Diabetes control and chronicity of the disease do not impact on the auditory system except for a subclinical involvement in the apical portion of the cochlea.

Type-2 diabetes mellitus and auditory brainstem response

OBJECTIVE

Diabetes mellitus (DM) causes pathophysiological changes at multiple organ system. With evoked potential techniques, the brain stem auditory response represents a simple procedure to detect both acoustic nerve and central nervous system pathway damage. The objective was to find the evidence of central neuropathy in diabetes patients by analyzing brainstem audiometry electric response obtained by auditory evoked potentials, quantify the characteristic of auditory brain response in long standing diabetes and to study the utility of auditory evoked potential in detecting the type, site, and nature of lesions.

DESIGN

A total of 25 Type-2 DM [13 (52%) males and 12 (48%) females] with duration of diabetes over 5 years and aged over 30 years. The brainstem evoked response audiometry (BERA) was performed by universal smart box manual version 2.0 at 70, 80, and 90 dB. The wave latency pattern and interpeak latencies were estimated. This was compared with 25 healthy controls (17 [68%] males and 8 [32%] females).

RESULT

In Type-2 DM, BERA study revealed that wave-III representing superior olivary complex at 80 dB had wave latency of (3.99 ± 0.24) ms P < 0.001, at 90 dB (3.92 ± 0.28) ms P < 0.001 compared with control. The latency of wave III was delayed by 0.39, 0.42, and 0.42 ms at 70, 80, and 90 dB, respectively. The absolute latency of wave V representing inferior colliculus at 70 dB (6.05 ± 0.27) ms P < 0.001, at 80 dB (5.98 ± 0.27) P < 0.001, and at 90 dB (6.02 ± 0.30) ms P < 0.002 compared with control. The latency of wave-V was delayed by 0.48, 0.47, and 0.50 ms at 70, 80, and 90 dB, respectively. Interlatencies I-III at 70 dB (2.33 ± 0.22) ms P < 0.001, at 80 dB (2.39 ± 0.26) ms P < 0.001, while at 90 dB (2.47 ± 0.25) ms P < 0.001 when compared with control. Interlatencies I-V at 70 dB (4.45 ± 0.29) ms P < 0.001 at 80 dB (4.39 ± 0.34) ms P < 0.001, and at 90 dB (4.57 ± 0.31) ms P < 0.001 compared with control. Out of 25 Type-2 DM, 13 (52%) had diabetic neuropathy, of which 12 (92%) showed abnormal BERA. In nonneuropathic [12 (48%)] only 6 (50%) showed abnormal BERA.

CONCLUSION

Delay in absolute latencies and interpeak latencies by BERA demonstrates defect at level of brainstem and midbrain in long standing Type-2 diabetes subjects, which is more pronounced in those with neuropathy.

Risk of developing sudden sensorineural hearing loss in diabetic patients: a population-based cohort study

OBJECTIVES

To explore the risk of development of sudden sensorineural hearing loss (SSHL) among diabetes mellitus patients.

STUDY DESIGN

A retrospective cohort study.

SETTING

Population-based study of Taiwan National Health Insurance Research Database.

PATIENTS

Approximately 26,556 newly diagnosed diabetic patients and 26,556 comparison subjects without diabetes mellitus were selected from claims made during 2000 to 2004.

MAIN OUTCOME MEASURES

The incidence of sudden sensorineural hearing loss (SSHL) at the end of 2009 was determined.

RESULTS

The incidence of SSHL was 1.54-fold higher in the diabetic group compared with the nondiabetic group (1.29 versus 0.78 per 1,000 person-years), and using Cox proportional hazard regressions, the adjusted hazard ratio (HR) was 1.592 (95% confidence interval [CI], 1.295-1.957). The risk of developing SSHL increased substantially to an HR of 2.060 (95% CI, 1.051-4.037), for patients who required triple antidiabetic medication compared with diabetic patients treated with a single antidiabetic drug. An increased risk of developing SSHL, with adjusted HRs of 1.574 (95% CI, 1.091-2.271) and 2.842 (95% CI, 1.880-4.295), was observed in diabetic patients with newly diagnosed comorbidities of retinopathy or retinopathy combined with renal insufficiency, which are both expected to reflect the severity of diabetes.

CONCLUSION

Diabetes mellitus was significantly associated with an increased risk of developing SSHL. Coronary heart disease or retinopathy comorbidities in diabetic patients seemed to be associated with an increased risk of developing SSHL. The risk of developing SSHL increased with the severity of diabetes.

Effects of the Chinese Yi-Qi-Bu-Shen Recipe extract on brainstem auditory evoked potential in rats with diabetes

This study was designed to investigate the effects of the Chinese Yi-Qi-Bu-Shen Recipe (YB) on brain stem auditory evoked potential (BAEP) in diabetic rats and on the protection of the diabetic rat brain's functional lesion. Thirty-three male rats were randomly divided into three groups: the normal control group (NC), the diabetic group (DM), and the diabetic rats treated with YB group (DM+YB). Blood glucose and body weight were measured every three weeks. After six weeks, the serum insulin, blood biochemical indices, superoxide dismutase, malondialdehyde, monoamine neurotransmitters, and BAEP were measured. Compared with the NC group, the waves III, V PLs, and the I-III, I-V IPLs of BAEP in the DM group were significantly delayed (all P<0.05). However, YB-treated diabetic rats maintained a normal brainstem function over the experimental period. Compared with the NC group, the waves I, III, V PL, and waves I-III, III-V and I-V IPLs of BAEP in the DM+YB group were very close (all P>0.05). On the other hand, compared with the DM group, the III, V PLs and the I-III, I-V IPLs of BAEP in the DM+YB group were significantly improved. It was discovered that the central conduction time of rats with diabetes had a close correlation with serum insulin, blood glucose, malondialdehyde, and insulin resistance index. Our results suggest that YB extract has a beneficial effect in preserving the brain's electrophysiological function in diabetic rats, likely through its antihyperglycemic activity, ability to reduce insulin resistance, and antioxidant activity.

Insulin and IGF-I prevent brain atrophy and DNA loss in diabetes

The aim of this study was to identify factors that regulate the bulk of adult brain mass, and test the hypothesis that concomitantly reduced insulin and insulin-like growth factor (IGF) levels are pathogenic for brain atrophy associated with impaired learning and memory in diabetes. Doses of insulin, or insulin plus IGF-I that were too small to prevent hyperglycemia were infused for 12 weeks into the brain lateral ventricles of streptozotocin-diabetic adult rats. Brain wet, water and dry weights were significantly decreased in diabetic rats; insulin prevented these decreases. The decrease in brain DNA and protein contents in diabetic rats was prevented by the combination treatment, but not by insulin alone. Levels of several glia- and neuron-associated proteins were reduced in diabetes; these reductions were also prevented by the combination treatment. Although hyperglycemia was not prevented in plasma or cerebrospinal fluid, insulin prevented brain atrophy but not bulk DNA loss in diabetes, whereas the combination prevented both. Insulin actively prevented the loss of brain water content as well. Brain atrophy is associated with concomitantly reduced levels of insulin and IGF in other disorders such as Alzheimer's disease.

Auditory brainstem evoked responses in insulin-dependent (ID) and non-insulin-dependent (NID) diabetic subjects with normal hearing

Hearing impairment has been reported to be one of the late complications of diabetes mellitus (DM), and the frequency varies. Previous data suggest that auditory brainstem potentials deteriorate long before the hearing impairment appears in patients with DM. Delay in neural conductance along the auditory pathway due to DM was assessed by means of auditory brainstem response (ABR) in 43 patients with normal hearing in a controlled study. Patients were classified according to age, presence of neuropathy. metabolic control, and duration and type of DM. ABR recordings revealed that absolute latencies of waves I, III and V were prolonged significantly in the diabetic group when compared to the control group (p < 0.05). When two diabetic groups (insulin-dependent and non-insulin-dependent) were compared with each other, the difference between the latency of wave I and the inter-peak latencies of I-III, III-V and I-V was not significant (p > 0.05). However, the difference between the latencies of waves III and V in the two diabetic groups was statistically significant. The duration of diabetes, blood glucose level and age were not associated with prolonged ABR latencies (p > 0.05). Prolongation of latency of ABR in patients with DM should alert us to possible damage to the auditory nerve, and close follow-up is needed in these patients.

Relationship of Type 2 diabetes to the prevalence, incidence and progression of age-related hearing loss

AIMS

Type 2 diabetes and associated microvascular abnormalities are postulated to affect hearing. Our study reports on the relationship between Type 2 diabetes and the prevalence, 5-year incidence and progression of hearing impairment in a representative, older, Australian population.

METHODS

The Blue Mountains Hearing Study is a population-based survey of age-related hearing loss conducted in a defined suburban area, west of Sydney. Hearing loss was defined as the pure-tone average of frequencies 0.5, 1.0, 2.0 and 4.0 kHz > 25 decibels hearing level (dB HL) in the better ear (bilateral hearing loss). Type 2 diabetes was defined from reported physician-diagnosed diabetes or fasting blood glucose > or = 7.0 mmol/l.

RESULTS

Age-related hearing loss was present in 50.0% of diabetic participants (n = 210) compared with 38.2% of non-diabetic participants (n = 1648), odds ratio (OR) 1.55 [95% confidence interval (CI) 1.11-2.17], after adjusting for multiple risk factors. A relationship of diabetes duration with hearing loss was also demonstrated. After 5 years, incident hearing loss occurred in 18.7% of participants with, and 18.0% of those without diabetes, adjusted OR 1.01 (CI 0.54-1.91). Progression of existing hearing loss (> 5 dB HL), however, was significantly greater in participants with newly diagnosed diabetes (69.6%) than in those without diabetes (47.8%) over this period, adjusted OR 2.71 (CI 1.07-6.86).

CONCLUSIONS

Type 2 diabetes was associated with prevalent, but not incident hearing loss in this older population. Accelerated hearing loss progression over 5 years was more than doubled in persons newly diagnosed with diabetes. These data explore further reported links between Type 2 diabetes and age-related hearing loss.

Interactions of hearing loss and diabetes mellitus in the middle age CBA/CaJ mouse model of presbycusis

Recently, we characterized the more severe nature of hearing loss in aged Type 2 diabetic human subjects [Frisina, S.T., Mapes, F., Kim, S., Frisina, D.R., Frisina, R.D., 2006. Characterization of hearing loss in aged type II diabetics. Hear. Res. 211, 103-113]. The current study prospectively assessed hearing abilities in middle age CBA/CaJ mice with Type 1 diabetes mellitus (T1DM) (STZ injection) or Type 2 diabetes mellitus (T2DM) (high fat diet), for a period of 6 months. Blood glucose, body weight and auditory tests (Auditory Brainstem Response-ABR, Distortion Product Otoacoustic Emissions-DPOAE) were evaluated at baseline and every 2 months. Tone and broad-band noise-burst responses in the inferior colliculus were obtained at 6 months. Body weights of controls did not change over 6 months (approximately 32 g), but there was a significant (approximately 5 g) decline in the T1DM, while T2DM exhibited approximately 10 g weight gain. Blood glucose levels significantly increased: 3-fold for T1DM, 1.3-fold for T2DM; with no significant changes in controls. ABR threshold elevations were found for both types of diabetes, but were most pronounced in the T2DM, starting as early as 2 months after induction of diabetes. A decline of mean DPOAE amplitudes was observed in both diabetic groups at high frequencies, and for the T2DM at low frequencies. In contrast to ABR thresholds, tone and noise thresholds in the inferior colliculus were lower for both diabetic groups. Induction of diabetes in middle-aged CBA/CaJ mice promotes amplification of age-related peripheral hearing loss which makes it a suitable model for studying the interaction of age-related hearing loss and diabetes. On the other hand, initial results of effects from very high blood glucose level (T1DM) on the auditory midbrain showed disruption of central inhibition, increased response synchrony or enhanced excitation in the inferior colliculus.

Efficacy of misoprostol in the treatment of tinnitus in patients with diabetes and/or hypertension

OBJECTIVE

To determine the efficacy of the prostaglandin E1 analogue misoprostol in the treatment of tinnitus in diabetic and/or hypertensive patients.

DESIGN

Double-blind, randomized, placebo-controlled trial.

SETTINGS

Tertiary care referral center.

METHODS

The subjects were 42 patients with hypertension and/or diabetes mellitus who had chronic tinnitus and had experienced tinnitus symptoms for a minimum of 6 months. Twenty-eight patients were randomly assigned to Group I (misoprostol treatment), and 14 patients to the Group II (placebo treatment). Misoprostol therapy was started at 200 microg per day, and was increased 200 microg every 7 days until a dose of 800 microg per day was reached. The same numbers of placebo tablets were given to the control group using the same schedule. Both groups were treated for 1 month. The changes in objective and subjective tinnitus findings from baseline to 1 month were assessed, and the group results were compared. The chi(2)-test, student's t-test and paired-samples t-test were used to analyze the study.

RESULTS

At the completion of treatment, objective assessment showed that tinnitus loudness decreased in 13 (46%) of the 28 patients in the experimental group, whereas this was observed in only two (14%) of the 14 subjects in the placebo group. Subjective tinnitus scoring revealed improvement rates of 29 and 14% for the misoprostol and placebo groups, respectively. When t-test relating to difference between rates were performed, the difference between improvement rate for tinnitus loudness of the experimental group and control group was found to be statistically significant (P = 0.05), but difference between improvement rate based on subjective tinnitus scoring was insignificant (P = 0.22).

CONCLUSION

Misoprostol is an effective and safe treatment for chronic tinnitus in hypertensive and/or diabetic patients. Our results are encouraging, but further studies of larger series are needed.

Brainstem auditory-evoked potential examinations in diabetic patients

Brainstem auditory-evoked potential (BAEP) examinations were performed in 15 patients with long-standing type-1 diabetes mellitus (DM). Cardiovascular reflex tests were applied for assessment of autonomic neuropathy. The aim of our investigation was to compare the BAEP results of this patient group with controls and to look for a possible correlation between the alteration of the auditory brainstem function and the cardiovascular autonomic neuropathy. Analysis of the latencies (waves I, II, III and V) and the inter-peak latencies (waves I-III and I-V) of BAEPs revealed a significant difference between diabetics and healthy controls. The amplitudes of waves I, III and V were definitely lower in comparison with those of healthy controls. A positive correlation was observed between the overall autonomic score and the latencies (waves III and V) and inter-peak latencies (waves I-III and I-V). These data support the hypothesis that long-standing DM and diabetic neuropathy might be related as a cause of certain dysfunctions of the central auditory pathways.

Early Identification of Hearing Impairment in Patients With Type 1 Diabetes Mellitus

OBJECTIVE

The aim of this study was to evaluate the cochlear micromechanics and central auditory function in patients with type I diabetes mellitus and to identify the site of possible dysfunction.

METHODS

Cochlear activity was evaluated by recording distortion product otoacoustic emissions (DPOAEs). DPOAEs were performed using an ILO 92 Otodynamics Analyser. Functional changes in the retrocochlear auditory pathway were evaluated by auditory brainstem responses (ABRs). DPOAEs and ABRs were measured in 42 normally hearing patients with type 1 diabetes mellitus aged 21 to 42 years, and 33 age- and sex-matched nondiabetic control subjects.

RESULTS

Both of the groups (diabetic and control) had normal and undifferentiated results in tonal and impedance audiometry. ABR peripheral transmission time (wave I) and central transmission time (interpeak latencies I-V) were significantly delayed in the diabetic compared with normal subjects, and the mean amplitudes of various DPOAEs were significantly reduced in the diabetic patients compared with the control subjects.

CONCLUSIONS

Combined use of different procedures for monitoring central and peripheral portions of the auditory pathway in diabetic patients showed alterations in cochlear micromechanics and the retrocochlear auditory pathway. Hearing impairment in diabetic patients is usually mild and subclinical, and can be detected early by accurate and objective audiometric methods.

An animal model of auditory neuropathy

OBJECTIVE

We describe an animal model of auditory neuropathy in which subjects have extensive, scattered inner haircell loss but with a relatively intact outer haircell population.

DESIGN

Such a pattern of cochlear haircell damage can be produced in the chinchilla by treatment with the anticancer agent carboplatin.

RESULTS

In these subjects, otoacoustic emissions (OAEs) and cochlear microphonics remain normal while auditory brain stem evoked potential (ABR) thresholds are significantly elevated. However, in the same subjects, central auditory neurons (in the inferior colliculus) have response thresholds that are considerably lower (by up to 50 dB) than ABR thresholds. These findings parallel the characteristics of auditory neuropathy in humans, in which absent or abnormal ABRs are recorded in patients with only mild to moderate audiometric thresholds and preserved OAEs.

CONCLUSIONS

We suggest that scattered inner haircell lesions also can result from long-term cochlear hypoxia, and we propose that this is a likely candidate for the etiology of many types of auditory neuropathy in human subjects.

Peripheral, but not central, nervous system abnormalities are reversed by pancreatic islet transplantation in diabetic Lewis rats

Neuroelectrophysiological recordings represent a non-invasive and reproducible method of detecting central and peripheral nervous system alterations in diabetes mellitus. In order to evaluate whether the normalization of metabolic control obtained by pancreatic islet transplantation could reverse diabetic neuroelectrophysiological alterations, or prevent further deterioration, we used an experimental model in which pancreatic islets (n = 1200) were injected into the portal vein of inbred Lewis rats (used as islet donors as well as recipients). Islets were injected 4 months after diabetes induction, since previous work had shown functional but not morphological damage at the nervous tissue level at this stage of the disease. Visual (V), brainstem auditory (BA) and somatosensory (S) evoked potentials (EPs) were measured in streptozotocin-induced, islet-recipient diabetic rats (n = 7), streptozotocin-induced diabetic rats (n = 16) and non-diabetic control rats (n = 12). Metabolic parameters and electrophysiological recordings were evaluated before diabetes induction, before transplantation and 4 months later. After transplantation, glycaemic levels returned to normal values within 1 week and remained so until the end of the study, as confirmed by a normal oral glucose tolerance test and by an increase in body weight. Electrophysiological recordings were altered in diabetic animals before transplantation. Four months after transplantation EP recordings improved, with a detectable gradient from the peripheral to the central structures. SEPs were significantly improved in the peripheral tarsus-L6 tract and the L6-cortex tract (P < 0.005 and P < 0.01 versus diabetic rats) and were ameliorated without achieving statistical significance in the central L6-cortex tract. BAEP latency values tended to improve in transplanted rats, but the differences versus non-transplanted diabetic animals failed to reach significance. VEP values remained clearly pathological and even deteriorated after transplantation. These results show that normalization of metabolic control by pancreatic islet transplantation can reverse some of the already established neuroelectrophysiological alterations at the peripheral nervous system level, but does not affect other alterations at the central nervous system level.

Changes in auditory P300 event-related potentials and brainstem evoked potentials in diabetes mellitus

To investigate the influence of diabetes mellitus on higher cognitive functions electrophysiologically, we studied auditory P300 event-related potentials (P300) in 40 NIDDM patients, taking into account wave I-V latencies (I-V) in auditory brainstem evoked potentials, clinical parameters and head MRI findings. Compared with 20 controls, diabetics had significantly longer P300 and I-V latencies. P300 latencies in diabetics correlated with neither I-V, HbA1, blood glucose levels, nor disease duration. Of the 13 diabetics investigated neuroradiologically, four had lacunar infarcts with prolonged electrophysiological values. The remaining nine had normal MRI scans, but their physiological parameters were still significantly longer than those of controls. These findings suggest that NIDDM can independently alter higher cognitive and the central auditory pathway functions. Our data also suggest that these alterations occur regardless of the recent metabolic derangement and disease duration. Cerebrovascular ischemia, if present, also appears to contribute in part to cognitive alterations.

Improvement of metabolic control does not normalize auditory brainstem latencies in subjects with insulin-dependent diabetes mellitus

INTRODUCTION

In our previous study (Am J Otolaryngol 14:413-418, 1993), we reported that prolonged auditory brainstem response latencies are associated with microvascular complications and the duration of diabetes in patients with insulin-dependent diabetes mellitus (IDDM). To investigate whether short-term improvement in metabolic control also affects ABR-responses, we compared ABR-latencies in subjects with IDDM before and after intensified insulin and diet therapy.

MATERIALS AND METHODS

Auditory brainstem latencies were measured in 13 subjects with IDDM (mean age: 25 years) before and after intensified insulin and diet therapy. The acoustic stimulus was a half sine wave with a duration of 0.250 millisecond and a frequency of 2,000 Hz. The stimulus was presented monaurally with fixed polarity through shielded headphones TDH-39 at repetition rate of 10 Hz and at 90 dB hearing level. All subjects had normal hearing ability. Glycated hemoglobin A1C (GHbA1C), blood glucose immediately before ABR-measurements, and mean blood glucose during 24 hours before auditory studies were measured before and after intensified therapy.

RESULTS

During intensified insulin therapy, GHbA1C improved significantly (P < .05) in study subjects. However, no changes were observed in ABR-latencies. We also studied those 10 patients whose blood glucose improved during intensified insulin therapy. Although blood glucose was significantly lower (P < .01) after intensified insulin therapy compared with that at baseline, no changes were observed between ABR-latencies at baseline and follow-up.

CONCLUSION

ABR-latencies were not affected by improvement in metabolic control in patients with IDDM. Our finding suggests that delayed ABR-latencies found in patients with IDDM are not caused by poor metabolic control of diabetes but rather by other mechanisms, for example, microvascular complications.

Hearing thresholds in insulin-dependent diabetic patients

Hearing thresholds were studied in 53 patients with insulin-dependent diabetes mellitus (IDDM) and 42 randomly selected non-diabetic control subjects, aged between 20 and 40 years. The hearing level tended to be worse in diabetic patients than in control subjects, but the differences were statistically significant only at frequencies of 6,000 and 8,000 Hz. Microvascular complications (retinopathy and nephropathy), and the duration of diabetes were associated with the elevated hearing thresholds. In contrast, poor metabolic control (high fasting blood glucose and glycated haemoglobin A1c) was not associated with increased hearing thresholds. The changes caused by diabetic neuropathy appeared simultaneously with microvascular complications and a long duration of the diabetes, and thus a causative role of diabetic neuropathy in the pathogenesis of elevated hearing thresholds remained unsolved. It was concluded that elevated sensorineural hearing thresholds at the frequencies of 6,000 and 8,000 Hz in patients with IDDM are probably caused by the long duration of diabetes and the microvascular complications associated with it.

Somatosensory evoked potentials in non-insulin-dependent diabetics with different degrees of neuropathy

Changes in median nerve somatosensory evoked potential (SEP) in diabetic patients have amply been reported. However the relationships between the diabetic polyneuropathy and the abnormalities of SEPs are still a matter of discussion. To elucidate these relationships, we have studied SEPs in 38 non-insulin-dependent diabetics with mild or severe degree of peripheral neuropathy. Our principal findings are as follows. (i) The wrist-Erb point (EP) conduction velocity (WECV) and the EP-N13 interpeak latency are significantly altered in diabetics. The N11-N13, N13-N20 and N13-P22, interpeak latencies are within the normal range. (ii) The WECV is more reduced in patients with severe neuropathy than in those with mild neuropathy, whereas the degrees of neuropathy have no influence on the alterations of EP-N13 interpeak latency. (iii) No significant correlation is found between the WECV and the EP-N13 interpeak latency. (iv) The WE conduction velocity was significantly correlated with both motor and sensory peripheral nerve conduction velocities. On the contrary, no correlation is found between these latter peripheral parameters and the EP-N13 interpeak latency. These findings indicate that the alteration in the tract from brachial plexus to the posterior column could not be a parallel process of distal neuropathy of non-insulin-dependent diabetic patients.

Acoustic-reflex responses in patients with insulin-dependent diabetes mellitus

PURPOSE

Patients with insulin-dependent diabetes mellitus (IDDM) are especially susceptible to microangiopathic complications such as nephropathy, retinopathy, and neuropathy. Microangiopathic changes are also the most important findings in histopathologic studies of the inner ear and central nervous systems in diabetic subjects. No previous studies have measured acoustic-reflex latencies (ARL) or amplitudes (ARA) in patients with IDDM. ARL and ARA reflect the function of the acoustic-reflex arch. Furthermore, possible changes in the tympanic membrane, ossicular chain, and stapedius muscle may affect the shape of acoustic-reflex.

SUBJECTS AND METHODS

Acoustic-reflex thresholds, latencies, and amplitudes were studied in 53 patients with IDDM and 42 randomly selected nondiabetic control subjects, aged between 20 and 40 years, using the Madsen Model ZO 73 Impedance Bridge (Madsen Electronics, Copenhagen, Denmark). Subjects with an abnormal tympanic membrane, conductive hearing loss, and known cause for hearing impairment eg, noise damage, were excluded from the study.

RESULTS

There were no differences between control and diabetic subjects in the contralateral acoustic-reflex thresholds. In contrast, patients with IDDM had longer ARLs and decreased ARAs compared with those of control subjects. ARA amplitude had linear correlation with the amplitude of tympanogram, whereas ARL had no linear correlation with auditory brainstem latencies in the same study subjects. Acoustic-reflex responses in insulin-dependent diabetic patients were not associated with the duration of diabetes, metabolic control, microangiopathy, or neuropathy.

CONCLUSIONS

Prolonged ARLs and decreased ARAs in patients with insulin-dependent diabetes are probably caused more by the stiff middle ear system than disturbances in the brainstem.

Auditory brainstem latencies in type I (insulin-dependent) diabetic patients

INTRODUCTION

This study was undertaken to compare auditory brainstem response latencies in insulin-dependent diabetics, and to compare these findings with metabolic control, microangiopathy, neuropathy, and the duration of diabetes.

METHODS

Auditory brainstem latencies were studied in 53 type I diabetic patients and 42 randomly selected nondiabetic control subjects, aged between 20 and 40 years. Three different stimulus repetition rates (10, 30, and 50 Hz) were used. All subjects had normal hearing ability.

RESULTS

Wave V latencies were longer in diabetic patients when compared with those of control subjects at all repetition rates. At repetition rates of 10 and 50 Hz, diabetic patients had a prolonged I-V interwave latency, and at a repetition rate of 50 Hz, diabetics had a longer III-V interwave latency than control subjects. These findings indicate a central disturbance in the auditory pathway. Microvascular complications (retinopathy, nephropathy) and the duration of diabetes were associated with the prolongation of auditory brainstem latencies. In contrast, poor metabolic control (high fasting blood glucose and glycated hemoglobin A1c) at the time of the present study was only marginally associated with prolonged auditory brainstem latencies. The changes in auditory brainstem latencies associated with diabetic neuropathy (measured with five cardiac autonomic nervous function tests) appeared simultaneously with microvascular complications and in patients with diabetes of long duration, and thus a causative role of diabetic neuropathy in the pathogenesis of prolonged auditory brainstem latencies remains unsolved.

CONCLUSION

Delayed auditory brainstem latencies in type I diabetic patients are probably caused by the long duration of diabetes and the microvascular complications associated with it.

Cognitive dysfunction in adults with type 1 (insulin-dependent) diabetes mellitus of long duration: effects of recurrent hypoglycaemia and other chronic complications

To examine the long-term effects of recurrent severe hypoglycaemia and other biomedical complications on mental efficiency, a battery of cognitive tests was administered to 142 Type 1 (insulin-dependent) diabetic adult patients (age 33.5 +/- 5.6 years; mean +/- SD) and 100 demographically similar non-diabetic control subjects. All diabetic subjects had been diagnosed before the age of 17 years. Diabetic subjects with one or more complications (distal symmetrical polyneuropathy; advanced background or proliferative retinopathy; overt nephropathy; one or more episodes of severe hypoglycaemia) performed significantly (p < 0.001) more poorly than non-diabetic control subjects on tests requiring sustained attention, rapid analysis of visuospatial detail, and hand eye co-ordination. Regression analyses indicated that the best biomedical predictor of cognitive test performance was a diagnosis of polyneuropathy. Although severe recurrent hypoglycaemia was not associated with performance on any test, the neuropathy x recurrent hypoglycaemia interaction term was significant. These results suggest that in adults with Type 1 diabetes of long duration, recurrent hypoglycaemia does not appear to influence cognitive performance directly, but may interact with neuropathy to exaggerate or otherwise magnify the extent of neurobehavioural dysfunction.

Tympanometry in patients with insulin-dependent diabetes mellitus

Tympanograms were studied in 53 patients with insulin-dependent diabetes mellitus (IDDM) and 42 randomly selected non-diabetic control subjects, aged between 20 and 40 years, using the Madsen Model ZO 73 Impedance Bridge. Subjects with abnormal tympanic membrane, conductive hearing loss and known reason for hearing impairment (e.g. noise damage) were excluded from the study. The mean tympanogram amplitudes in diabetic patients were significantly lower in both ears than those of control subjects. The duration of diabetes and microvascular complications (nephropathy and retinopathy) were associated with decreased amplitudes. These findings indicate that decreased tympanogram amplitudes in patients with IDDM are probably caused by diabetes of long duration and the microvascular complications associated with it.

Diabetes-induced alterations of central nervous system G proteins. ADP-ribosylation, immunoreactivity, and gene-expression studies in rat striatum

Previous studies from our laboratory have suggested that diabetes-associated central nervous system abnormalities are characterized by progressive alterations of neurotransmitters and of transductional Gi/Go proteins. In this study, we have further characterized these abnormalities in the striatum of alloxan-diabetic rats by means of adenosine 5'-diphosphate (ADP)-ribosylation, and Western and Northern blotting techniques. Fourteen weeks after diabetes induction, pertussis-toxin (PTX) catalyzed ADP-ribosylation of Gi/Go proteins was markedly reduced in diabetic animals, as shown by a clear decrease of 32P-ADPribose incorporation into G protein alpha subunits. In agreement with our previous pharmacological studies that showed a reduction of Gi-mediated modulation of adenylate cyclase activity only at this stage of diabetes, no changes in PTX-mediated ADP-ribosylation were observed earlier (5-wk diabetes). Immunoblotting studies performed by using antibodies selectively raised against Gi-2, Go, and Gs proteins did not reveal any differences between control and diabetic animals at any stage of diabetes. Similarly, the mRNAs corresponding to the alpha subunits of Gi-2, Go, and Gs proteins did not show any marked changes in chronic diabetic rats with respect to control animals. It is therefore concluded that diabetes is associated with development of a time-related alteration of cerebral Gi/Go proteins and that this defect is not owing to gross changes in either content of G proteins or mRNA level, but probably reflects modifications of G protein's structure or physiological status affecting the coupling with membrane effector systems and the sensitivity to PTX.

Brainstem auditory evoked potentials in rats with streptozotocin-induced diabetes

Brainstem acoustic evoked potentials (BAEPs) were studied in streptozotocin (STZ)-diabetic rats and age-matched controls at 3 and 5 months from induction of the pathology. The diabetic status of the animals was kept uncontrolled throughout the study. Body weight and glycosylated hemoglobin were markedly altered in the diabetic animals (-42%, and +120% of control values, respectively). Neurophysiological results showed an increase in the latency of the major components of BAEPs; this increase was clearly time-dependent for the peripheral component (peak I). The central component (peak IV) was also significantly delayed. However, no significant impairment of the central conduction time was demonstrated by examining the interpeak I-IV latency. In conclusion, BAEPs prove to be a useful non-invasive neurophysiological technique that may help unravel both the relative involvement of the peripheral and central nervous systems in the course of diabetes mellitus, and the evolution of diabetic neuropathy.

Early alterations of Gi/Go protein-dependent transductional processes in the retina of diabetic animals

The early alterations of G-protein-dependent transductional mechanisms have been characterized in the retina of alloxan-treated diabetic rats. Five weeks after alloxan injection, pertussis toxin radiolabeling of Gi/Go proteins was markedly reduced in the retina of diabetic animals, suggesting either a reduced expression and/or the presence of some structural modification of these G-protein subtypes. The functional activity of Gs proteins, measured as stimulation of membrane adenylate cyclase by dopamine, did not seem to be impaired at this stage of the pathology; basal adenylate cyclase activity was indeed increased in diabetic rats, consistent with the observed reduction of Gi/Go inhibitory proteins. Such functional alterations of the cAMP producing system were causally related to diabetes induction, since they were reversed by treatment of diabetic animals with insulin. These results suggest that G-protein dependent transduction mechanisms are altered in the retina of diabetic animals, and that a defect of Gi/Go proteins could represent an early transductional damage in the development of diabetic retinopathy.

Hearing problems and hormonal disturbances in the elderly

The most frequent hormonal diseases attracting audiological interest are hypothyroidism (myxodema) and diabetes mellitus. For many years these diseases have been considered to cause hearing disorders with the lesion located predominantly in the inner ear and central auditory pathways, resulting in sensorineural hearing loss. However, the causal relationship between hearing loss and hypothyroidism has been questioned, and thus a study was undertaken to elucidate this problem. A sample of hypothyroid patients (n = 15) with a median age of 76 years (range 61-92) underwent audiological examination before and after treatment with L-thyroxine (average 5 months; range 2-12), and re-examination (n = 13) after an observation period of average 40 months (range 32-46). No significant improvement in their hearing thresholds, speech reception thresholds or discrimination scores could be demonstrated, and the hearing ability in the hypothyroid patients did not differ significantly from that found in an age- and sex-matched population. In addition, histological investigation of the temporal bones from an 83-year-old woman with myxoedema showed no morphological changes or deposition of glycosaminoglycans. Audiological examinations in patients with insulin-dependent diabetes mellitus also show contradictory results. Therefore, the cochlear and retrocochlear hearing functions were evaluated in 20 patients with diabetic microangiopathy with a median age of 41 years (range 25-66), and in 19 patients without microangiopathy with a median age of 27 years (range 17-42). No significant differences in hearing thresholds or discrimination scores were present between the two diabetic groups, nor was any difference found between the diabetic patients and an age- and sex-matched population. In the patients with long-term insulin-dependent diabetes mellitus, brainstem audiometry revealed abnormal responses in 40%, indicating the presence of diabetic encephalopathy.

Central nervous system involvement in elderly patients with non-insulin-dependent diabetes mellitus

We examined cognitive functions and central conduction velocities in 20 patients, over 63-year old, with NIDDM compared with 20 normal, age-matched controls. Mean conduction velocity of median nerve, was significantly lower in diabetics than in controls, but absolute values were within normal range. Neurological examination showed clinical signs of lower limbs neuroperipheral involvement. Only one cognitive subtest performance was abnormal whereas there was no impairment in central conduction velocities. In our study population, although median nerve conduction velocity values may introduce a bias of low peripheral neuropathy incidence, there was no evidence of a massive or progressive specific central nervous system involvement caused by NIDDM.

Denervation and hyperinnervation in the nervous system of diabetic animals: III. Functional alterations of G proteins in diabetic encephalopathy

G protein-mediated effects on cAMP production were evaluated in the corpus striatum of diabetic rats 5 and 14 weeks after alloxan injection by measuring both D1-receptor-induced stimulation and D2-receptor-mediated inhibition of adenylate-cyclase activity. At 5 weeks of diabetes, no obvious alterations of G protein functions were detected. Both dopamine-stimulated adenylate cyclase and bromocriptine-induced inhibition of enzyme activity were indeed similar in control and diabetic animals. Fourteen weeks after alloxan injection, profound alterations were observed. Dopamine-stimulated cAMP production was markedly increased in diabetic rats, whereas bromocriptine ability to reduce cAMP formation was almost abolished at this late stage of diabetes. Hypoactivity of Gi/Go proteins was also confirmed by the reduced ability of the GTP non-hydrolyzable analog GTP-gamma-S to inhibit forskolin-stimulation of adenylate cyclase. These results show an apparent functional imbalance between Gs and Gi/Go-mediated transduction mechanisms, with an increased efficacy of Gs activity likely due to the loss of Gi/Go inhibitory functions. Concomitantly with such transductional alteration detected in chronic diabetes, we observed a marked increase of the striatal content of met-enkephalin, which is known to utilize Gi/Go proteins for inhibition of adenylate cyclase. The measurement of other transmitters (vaso-active intestinal peptide, substance P, serotonin, noradrenaline, and dopamine) did not reveal any difference with respect to controls. The observed transductional defect in diabetic animals and the increased content and/or hyperinnervation by the metenkephalinergic system could be correlated as mutual compensatory mechanisms.

Denervation and hyperinnervation in the nervous system of diabetic animals. II. Monoaminergic and peptidergic alterations in the diabetic encephalopathy

The monoaminergic innervation of the central nervous system (CNS) is characterized by long and short projecting neurons. The neurological correlates of diabetes are usually referred to as processes of degenerative atrophy affecting motor and sensory peripheral nerves. We have found that the long serotoninergic axons innervating the spinal cord and the cerebral cortex are unaffected in diabetic animals and that the noradrenergic innervation of the cortex is normal as well. The serotonin content is doubled in the hypothalamus with no apparent alteration of 5-HIAA levels, suggesting a supernumerary innervation that is accompanied by a reduced release. In pons medulla oblongata, serotonin and dopamine with the relative metabolites 5-HIAA and DOPAC are significantly reduced, whereas noradrenaline is markedly increased. In the hippocampus, there is a reduction of serotonin content. The serotoninergic alterations are peculiar as suggested by the sparing of the most distal projections that is accompanied by hyperinnervation of the hypothalamus and the loss of shorter collaterals in the pons medulla oblongata. In the hypothalamus and in the striatum of diabetic rats, there are significant higher levels of substance P and met-enkephalin, respectively. The abundance of proenkephalin A mRNA is also increased in the striatum. Conversely, in the lumbar cord of diabetic animals, the levels of substance P and met-enkephalin are significantly reduced. Such alterations likely reflect retrograde degeneration of the peripheral sensory input. The CNS changes are unlikely due to vascular abnormalities in the brain of diabetic rats; rather, we suggest that the persistent lack of insulin is the major factor involved as a trigger of the monoaminergic changes in the diabetic brain.

Clinical utility of somatosensory evoked potentials in diabetes mellitus

The posterior tibial nerve and median nerve somatosensory evoked potentials (PTN-SEPs and MN-SEPs) were investigated in 34 patients with diabetes mellitus (DM). We measured the latency of the first positive cortical potential (the cortical P37) of PTN-SEPs and that of the first negative cortical potential (the cortical N18) and Erb's potential of MN-SEPs. In 18 patients (52.9%), the cortical P37 latency was more than 3 SD longer than normal in the tibial nerve. There were positive correlations between the latency of cortical P37 and the duration of DM and the motor nerve conduction velocity of the posterior tibial nerve. Sensory action potentials of the posterior tibial nerve were not detectable in 21 patients, though cortical P37 potential was unambiguously recorded by stimulating the posterior tibial nerve even in those subjects. Diabetic retinopathy and nephropathy also tended to rise with increasing latency of cortical P37. The latency of cortical P37 is an important parameter in assessing diabetic neuropathy.

Delayed brainstem auditory evoked responses in diabetic patients

The incidence of subclinical central diabetic neuropathy is unclear due to difficulty in detecting latent alterations of central neural transmission process. The aim of this study was to evaluate a central neuroconductive mechanism in diabetics by brainstem auditory evoked responses (BAER). We found increased latencies of peaks I, III, V in diabetics as compared to control subjects. These BAER abnormalities were demonstrated in 62 per cent of insulin-controlled diabetics and in 33 per cent o patients treated by diet, or peroral drugs. No alterations in brainstem responses were observed in patients with latent diabetes. We did not find any correlation between the BAER abnormalities and the duration of the disease, the blood glucose level or the level of control of the diabetes.

Neuropsychiatry and child psychiatry: the case of the brainstem evoked potential as an illustration

In child psychiatry one may frequently and reasonably suspect the existence of a neurophysiological abnormality of some kind even though this abnormality is not detectable with readily available technology: in children presenting developmental or acquired aphasia, in some specific learning disabilities, in severe developmental disorders or perhaps in a subgroup of those labeled Attention Deficit Disorder. 1. The importance for us as child psychiatrists to keep in mind the possible role of neurophysiological factors is put into perspective. 2. What Evoked Potentials are is briefly described as well as the basic principles of the technique used in recording them. 3. A review of the literature reveals how the Brainstem Auditory Evoked Responses (BAER) have helped in understanding unknown facets of known diseases (Diabetes, Hyperthyroidism, Bell Palsy, etc. . . . ) from this, it is argued that this is reasonable to expect the same usefulness for diagnosis in child psychiatry. 4. An opinion is offered as to how and when a child psychiatrist should make use of this investigation.

Evaluation of central nervous conduction by visual evoked potentials in insulin-dependent diabetic children. Metabolic and clinical correlations

Peripheral neuropathy is a well-known complication of diabetes, but few data are available on central lesions. Visual evoked potentials (VEPs) seem a reliable and feasible technique for detecting a conduction delay in the central nervous system. Seventy-one insulin-dependent type 1 diabetic children (mean age 15 +/- 3 years) and 33 controls were investigated for central neuropathy. We used a pattern of reversal stimulation with television display of a checker board pattern (15 min and 30 min check size). The latencies of the positive peak (P100 wave) were significantly lengthened in 17 patients (27%) but no correlation was found between VEPs and age, duration of diabetes, insulin requirement and HbA1 level. A negative correlation was found between VEPs and peripheral nervous conduction velocity. VEPs measurement seems a simple and reliable technique for detecting early alterations in CNS function in diabetics. Our data suggest that central and peripheral nervous alterations progress simultaneously.

Auditory brainstem evoked potentials in insulin-dependent diabetics with and without peripheral neuropathy

Auditory Brainstem Evoked Potentials (ABEP) were recorded from 33 insulin-dependent diabetes mellitus (IDDM) patients (17 with diabetic peripheral neuropathy and 16 without) as well as from 20 normals. Pure-tone audiometry, speech reception threshold and discrimination were also evaluated. Sub-clinical pure-tone threshold elevation was observed for IDDM patients with neuropathy. Pure-tone thresholds of IDDM patients without neuropathy were not significantly different from those of normals. ABEP abnormality (at 10/sec click rate) was observed in 31% of IDDM patients with neuropathy, rising to 44% when 55/sec click rate measures were included. Abnormalities included bilateral and symmetrical peak-latency prolongations for all waves, greater for the later waves, and prolongation of V-I and V-III interpeak latency differences, all at 10/sec, and only prolonged peak latency for I at increased rate. Abnormalities coincided with microangiopathy and peripheral neuropathy. The incidence of ABEP abnormality for IDDM patients without neuropathy was only 12%, unilateral and sporadic in nature. As a group, IDDM patients with neuropathy had significantly prolonged IV and V peak-latencies, compared with the normals, or with the IDDM patients without peripheral neuropathy. In contrast, IDDM patients without neuropathy resembled the normals in all respects. ABEP have proven useful in understanding the variety of pathologies underlying the clinical manifestation of diabetes.

Delayed brainstem auditory evoked responses in experimental diabetes mellitus

The brainstem auditory evoked responses (BAER) were utilized for the evaluation of central neural transmission in alloxan-induced diabetes in rats. The mean latencies of waves I, III, V and the interpeak latencies III-V and I-V were prolonged in diabetic rats as compared to the same rats before alloxan administration. The incidence of abnormal BAER was more frequent in the group of rats with severe diabetes (82 per cent) than in mildly diabetic animals (42 per cent). Our results may suggest the presence of a central neuropathy in experimental diabetes, which can be detected by the method of BAER.

Brainstem auditory and visual evoked potentials in type 1 (insulin-dependent) diabetic patients

Brainstem auditory evoked potentials and pattern shift visual evoked potentials were measured in 34 Type 1 (insulin-dependent) diabetic patients with long-standing disease and in 43 control subjects. Thirty-two percent of diabetic patients had abnormal brainstem auditory evoked potentials and 15% had abnormal visual evoked potentials. These abnormalities were not related to duration of diabetes, diabetic control or individual diabetic complications (retinopathy, nephropathy, peripheral or autonomic neuropathy). The aetiology of the abnormalities must remain a subject for speculation. The findings of this study are consistent with a central diabetic neuropathy involving the brainstem in long-standing diabetic patients.

Auditory and somatosensory far-field evoked potentials in diabetes mellitus

The effects of insulin dependent diabetes mellitus (IDDM) on brainstem auditory evoked potentials and early components of somatosensory evoked potentials were evaluated in 10 young IDDM patients and 10 control subjects. The IDDM group showed significantly longer intervals between major components of both types of evoked potentials. The results indicated that IDDM patients are at risk for central as well as peripheral neuropathy.

Psychiatric aspects of diabetes mellitus

A descriptive study of the psychiatric findings in 50 insulin--dependent diabetics is presented. Among the symptoms found were a marked reduction in energy level, increased fatigue and irritability, depression, and delayed psychosexual maturation. Diabetes mellitus is commonly considered to be a disease that, if properly controlled, allows the patient to lead a relatively normal life. We found, however, that these symptoms often made the patients' lives uncomfortable, reduced their functional capacity, disrupted their family life, and disturbed the adolescence of those who were affected at an early age.

Involvement of central nervous system in diabetes mellitus

Brainstem auditory evoked responses were recorded in 22 diabetic patients with a variable duration of illness (mean 5.8 years) and 14 normal healthy controls of comparable age. The initial 10 millisecond components, found to be most consistent and reproducible, were analysed. Variations in the form of individual wave latency, interpeak latencies and V wave amplitude were compared in both the groups. No difference was found in any of the parameters. It was concluded that central neural pathways are not involved at least initially in diabetes mellitus.