Biomedical subjects

K Ribarić

Publications and source records attributed to K Ribarić.

8 recordsLinked to original sources

PubMed1992

On the capability of the vestibular apparatus to perceive sound stimuli.

This paper discusses the capacity of sound perception in 5 profoundly deaf subjects in whom a "fenestra" was previously formated on the lateral semicircular canal. The ability of sound and vibration perception after fenestra formation in profoundly deaf subjects with normal function of the vestibular apparatus has been described previously. The experiments for this procedure were done on pigeons by Wit & Bleeker. The subjects aged from 22 to 34 years. Causes of deafness varied. Their hearing threshold was bilaterally higher than 95 dB HL and their vestibular apparatus was of normal excitability bilaterally when tested with a caloric test. In all 5 patients the ear conduction hearing threshold remained the same, but the ability of vibration perception improved significantly, and ranged postoperatively between 30 and 45 dB HL. The frequency dynamic range was from 125 to 2,000 Hz in 4 subjects, and from 125 to 4,000 Hz in 1 subject. The patients claimed to have perceived higher intensities, but with a variable dynamic range from frequency to frequency. The intensity range amounted to between 15 and 40 dB. The obtained data of vibration perception ability are discussed.

Adult↗

PubMed1991

Can size or type of the pontocerebellar tumor be predicted by an ABR finding?

ABR waveforms were analyzed in 63 subjects with tumors of the pontocerebellar angle. The tumors were diagnosed by CT scan and the diagnoses were surgically confirmed. According to the latency changing and amplitude size, the ABR waveforms were classified into seven types (0, A, B, C, D, E and F). All tumors were divided into groups (depending on size), and into subgroups (depending on type). Types 0-E were found in tumors of all sizes. Type C of the brain stem response (BSR) waveform (only 1 deflexion present) was revealed in 75% of tumors greater than 20 mm. In this case tumor size may be predicted with the significance level of 5%. Type F of the BSR waveform was found in tumors other than neuromas. Contralateral BSR is affected by tumors greater than 20 mm, and from the statistic point of view significantly more often by neuroma (significance level 5%) than by other tumors.

Audiometry, Evoked Response↗

PubMed1984

Frequency-following response evoked by acoustic stimuli in normal and profoundly deaf subjects.

A low-frequency acoustic stimulus was applied to the right mastoid, the right acromion and the distal phalanx of the right index finger in 10 healthy and 10 profoundly deaf subjects. The stimulus, which had a frequency of 80-120 Hz, was delivered by means of a special vibrating system, constructed for this purpose. The frequency-following response (FFR) was recorded. In all the healthy subjects, FFR appeared with a latency of about 6 ms from the stimulus onset and with a peak-to-peak amplitude of 0.3-1.2 microV. Also, in all the deaf subjects, a change in bioelectrical activity was recorded, which reproduced the stimulus frequency at a latency of about 6 ms and with a peak-to-peak amplitude of 0.3-1.2 microV. Afferent pathways by which the stimulus could be transmitted in deaf subjects are discussed.

Acoustic Stimulation↗

PubMed1980

Improved contingent negative variation audiometry.

In earlier reports we described contingent negative variation audiometry (CNV-A) and explored the accuracy of the method used in clinical conditions. Amplitude was found to be the factor which determines the accuracy of CNV-A. With this study we aimed to increase the amplitude of the CNV so as to improve the accuracy of CNV-A. The amplitude of the CNV is dependent on the content of the information of the S2 stimulus in the CNV paradigm. For this purpose we used a light stimulus (red or green) for the S2. The patient had to recognize the stimulus and act accordingly. The tests were performed on 12 volunteers in whom we simultaneously registered the CNV and the slow vertex response. The amplitude of the CNV was on average higher than with the previous CNV-A methods. The mean value of the absolute difference of the results between CNV-A and subjective tonal audiometry (ADG) was 6.9 +/- 5.5 dB. The mean difference between the results of both methods, however, was only 4.3 +/- 7.8 dB. The new CNV-A method is more accurate than the previous one. Nevertheless, we believe that not all possibilities for the improvement of the method have been explored. By taking into account the psychological factors which influence the amplitude of the CNV, and with a better computer analysis of the recordings, it will probably be possible to obtain even more accurate objective data on the threshold of perception of auditory stimuli with the aid of CNV-A.

Adult↗

PubMedDate not supplied

Electronystagmography in the pathology of the central nervous system.

The program of the electronystagmographic examinations in the pathology of the central nervous system contains 11 groups of tasks. Sixty signs of central impairments are listed, from which 26 nystagmic irregularities had a small diagnostic value. No sign occuring alone could be taken as pathognomonic, only a group of signs can be used for the impairment localization. Besides for the peripheral vestibular and the peripheral vestibulocochlear impairments, the authors succeeded to make a group containing pathogomonic signs for mixed vestibular impairments as well as for multiple sclerosis affecting vestibular structures.

Central Nervous System Diseases↗

PubMedDate not supplied

Frequency following response evoked by vibratory stimuli in profoundly deaf subjects.

A vibratory stimulus at a frequency of about 100 Hz was transmitted through a bone conductor on the mastoid in 26 profoundly deaf subjects. In all of them, the function of the vestibular apparatus was tested by means of the Fitzgerald-Hallpike caloric test. In some of the deaf subjects, evoked potentials were recorded, which following the frequency of the stimulus and which according to amplitude and latency characteristics, corresponded to the frequency following response (FFR). A close correlation was found between the normal function of the vestibular apparatus and the appearance of FFR in deaf subjects. The possible receptors of the stimulus and the afferent pathways which generate the recorded response are discussed.

Acoustic Stimulation↗

PubMedDate not supplied

Auditory potentials in profoundly deaf subjects.

In 12 healthy volunteers, and 5 prelingually and 5 postlingually profoundly deaf subjects, a 500 Hz filtered click stimulus was applied to the mastoid via the bone conductor. In all the healthy volunteers, middle latency response (MLR) was recorded. Among all profoundly deaf subjects, MLR was recorded only in 2 with prelingually deafness; these two subjects were also the only ones with normal vestibular function. The possible mechanisms of the MLR appearance in deaf subjects are discussed.

Adolescent↗

PubMedDate not supplied

Endocrine responses to head and neck surgery in men.

It has been well established that surgical stress leads to profound changes in endocrine function and metabolism. However, the endocrine response varies depending upon the type and the extent of surgery. As no data were available about the endocrine changes during and following major head and neck surgery, this study was performed. Plasma levels of adrenocorticotropin (ACTH), cortisol, thyroid-stimulating hormone (TSH), thyroxin (T4), triiodothyronine (T3), growth hormone (GH), prolactin (PRL), gonadotropins (LH and FSH), oestradiol and testosterone were determined in 17 patients one day before, immediately after, as well as 2 and 4 days after head and neck surgery. An increase in ACTH, cortisol, PRL and GH, and a decrease in plasma oestradiol and testosterone values occurred immediately after surgery. There was a slow fall in cortisol levels after surgery, but they remained elevated even on the fourth postoperative day, whereas GH values returned on the fourth day to the initial level. There were no changes in gonadotropins, TSH and T3, but T4 values were found to be increased on the second and fourth postoperative day. The prolonged cortisol stimulation which was not described by other researchers after other kinds of surgery might be caused by vagal stimulation during and/or after head and neck surgery. Increased needs after a major head and neck surgery could explain the increment of T4 values.

Adrenocorticotropic Hormone↗