Hereditary motor and sensory neuropathy Lom type in a Serbian family.

Hereditary motor and sensory neuropathy Lom type (HMSNL), also called CMT 4D, a hereditary autosomal recessive neuropathy, caused by mutation in N-Myc downstream regulated gene 1 (NDRG1 gene), was first described in a Bulgarian Gypsy population near Lom and later has been found in Gypsy communities in Italy, Spain, Slovenia and Hungary. We present two siblings with HMSNL, female and male, aged 30 and 26, respectively in a Serbian non-consanguineous family of Gypsy ethnic origin. They had normal developmental milestones. Both had symptoms of lower limb muscle weakness and walking difficulties with frequent falls, which began at the age of seven. At the age of 12, they developed hearing problems and at the age of 15 hand muscle weakness. Neurological examination revealed sensorineural hearing loss, dysarthria, severe distal and mild proximal muscle wasting and weakness, areflexia and impairment of all sensory modalities of distal distribution. Electrophysiological study revealed denervation with severe and early axonal loss. Sensorineural hearing loss was confirmed on electrocochleography and brainstem evoked potentials. Molecular genetic testing confirmed homozygote C564t (R148X) mutation in NDRG1 gene.

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.

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.

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.

Perception of audio-frequency vibrations by profoundly deaf subjects after fenestration of the vestibular system.

A survey is given of the literature on the sensitivity of the vestibular system to audio-frequency sound and vibration in animals. It is also shown that responses to such stimuli can be evoked in man. On the basis of these results it was decided to perform a fenestration of the horizontal semicircular canal in three profoundly deaf volunteers, with normal sensitivity of the vestibular system. The first results are promising: the threshold for audio-frequency vibration in the operated ears improved markedly. Furthermore, the subjects reported perception of environmental sounds using a bone conductor hearing aid.

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.

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.

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.

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.

Evoked cerebral potential audiometry and hearing threshold.

Audiometric testing by means of the nonspecific evoked cerebral potential (NECP) was performed in 20 children (11 with normal hearing, 6 with conductive and 3 with sensorineural hearing loss). The threshold as determined by this method was 20-30 dB higher than the threshold of the subjective tonal audiograms in the majority of the cases. Only in two cases the difference was up to 70 dB. There were no significant differences between the results of the methods in the three groups of children. The possible reasons for the described discrepancy between the thresholds of the ECP audiometry and the subjective tonal audiometry are discussed. It is pointed out that either of the two methods explores one of two different functional systems: the nonspecific activating system of the brain stem and the auditory pathway. It is suggested that the observed discrepancy between the results of the two methods may mainly be due to different thresholds of the two systems. To avoid false negative results of the ECP audiometry in subjects with 'constitutionally' low amplitude of the NECP it is proposed to routinely determine the amplitude of the NECP produced by somatosensory stimuli. Careful evaluation of the recorded data can improve the diagnostic value of ECP audiometry.

Contingent negative variation audiometry in children.

The aim of the present work was to establish whether contingent negative variation audiometry (CNV-A) is applicable to children. In a group of 23 children aged 5-7 years, only 10 generated clearly recognizable CNV when tested with the method successfully used in adults. When the procedure was modified by prolonging the S1-S2 interval and by introducing attractive slides to serve as the S2 stimulus and by adopting a slower repetition rate, 9 children randomly selected from the former group generated high-amplitude CNV (10.1 +/- 4 mu V). The CNV-A measurements involving a longer auditory stimulus (S1), lasting nearly to the beginning of S2, and an even slower repetition rate were equally successful in 18 children aged 3-5 years, who generated CNV with an average amplitude of about 9 mu V (range 5-15 mu V). We believe that the basic problem of successful CNV recording in children is to attract their attention to the signals of the CNV paradigm. The child's attentiveness decreases rapidly. The mean difference and the absolute mean difference between the subjective hearing threshold for white noise and the perception threshold for white noise as determined by CNV-A were as follows: 8.8 +/- 8 dB (both values) for the older group, and 3 +/- 10.4 and 8.6 +/- 6.5 dB, respectively, for the younger group. These differences are quite comparable to those obtained in adults. We therefore believe that CNV-A, used in combination with the behavioral method, provides a most reliable estimate of the child's hearing threshold in dubious situations.

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.