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.

Lesion detection in MS patients with and without clinical brainstem disorders: magnetic resonance imaging and brainstem auditory evoked potentials compared.

The findings of the present study can be summed up in the following points: (1) brainstem auditory evoked potentials (BAEP), as compared with magnetic resonance imaging (MRI), has a greater capacity and a lower cost in disclosing brainstem plaques both in MS patients with symptoms or signs of actual brainstem involvement and in clinically silent ones. This makes BAEP a useful technique for the neurologist, who can confirm the clinical suspicion of a brainstem lesion and follow the evolution of the disease in the patient. (2) The sensitivity of BAEP is lower than that of MRI as far as the anterior lesions of the brainstem are concerned. (3) MRI is more specific than BAEP, inasmuch as several types of injuries can alter the BAEP, while the demyelinating plaque has a specific image and can only be confused with little lacunar infarcts. (4) Plaques that produced symptoms or signs in the past can eventually disappear and be no longer detected by a subsequent MRI.

A method of digital filtering to enhance the peaks of evoked potentials: application to auditory brainstem responses.

The aim of this paper is to propose a method of data processing for the analysis of evoked potentials, in particular for auditory brainstem responses. The present method has been developed to simplify and speed up the interpretation of the recordings by means of an enhancement of the response peaks. Even for experienced observers, identification of the response waves and subsequent latency measurements may sometimes constitute a difficult task, due to the presence of residual noise or to interference between the temporal waveforms of adjacent peaks and troughs. The method is implemented with a digital non-causal (zero-phase shift) filter, based on the convolution with a finite impulse response, to make the computation time compatible with the use of low-cost microcomputers. The performance is shown to be very good in several examples.

The relationship of head and brainstem size to main parameters of ABR in the developmental age and in adults.

In a previous investigation the relationship between head size and main parameters of ABR, i.e. waves absolute latencies and interwave delays, was studied in 55 subjects (1). Significant and positive correlation coefficients were found between I-V I.P.I. and the sum of head circumference, nasion-inion, and intertragal distances in the age range 7 to 11 years only and not in adult age. The purpose of the present study was to verify whether in 11 adults a correlation could be demonstrated between ABR parameters and two axial measures of brainstem length, calculated on MRI views. A positive and significant coefficient was found to exist between these measures and I-V I.P.I. and wave V absolute latency.

Auditory evoked potentials test battery related to magnetic resonance imaging for multiple sclerosis patients.

The results of the recording of the Auditory Brainstem Responses (ABR) in 32 patient with "definite" multiple sclerosis (MS) according to Poser et al. (1983) were contrasted with the brain stem anatomic lesions evidenced by Magnetic Resonance Imaging (MRI) and with the neurologic signs and symptoms found at clinical examination (BS). Twenty-one patients showed ABR abnormalities (65.5%); in 15 cases MRI visualized demyelinization plaques in the brain stem (46.8%); 12 patients had neurological signs of brain stem involvement (37.5%) at the time of the electrophysiological and radiological assessment. When the observation was restricted to the group of 21 patients with past or present BS neurological signs, ABR sensitivity resulted 81% (17/21), while MRI obtained a value of 57% (12/21).