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T S Prevec

Publications and source records attributed to T S Prevec.

29 records · Page 2Linked to original sources
PubMedDate not supplied

Epidurally recorded cervical spinal activity evoked by electrical and mechanical stimulation in pain patients.

Spinal SEPs to electrical and mechanical stimulation of the upper limb of the non-painful side in 7 pain patients were recorded from the cervical epidural space. In response to electrical stimulation of the median nerve, the longitudinal distribution of the spinal postsynaptic negativity (N13) along the cord had a distinct level of maximal amplitude at the C5 vertebral body. When recorded at increasing distances cranial or caudal to this level, the latency of N13 was successively prolonged, in agreement with a spread-out near-field generator in the dorsal horn. Similar patterns of distribution and levels of maximal amplitude were demonstrated for the N13 wave evoked by electrical stimulation of the ulnar and thumb nerves as well as by mechanical stimulation of the thumb ball. The amplitude ratios of the N13 waves evoked by electrical stimulation of the median nerve and the thumb nerves, and by mechanical stimulation of the thumb ball were 3.9 to 1.4 to 1. The slow positive wave (P18), which has been assumed to represent recurrent presynaptic activity, had a somewhat different distribution, with a lower maximal amplitude and a less marked falling off in amplitude along the cord, as compared to the N13 component. The initial presynaptic positivity (P10) appeared with an almost constant amplitude along the cord. Tactile stimuli produced responses with considerably longer latency and duration than those obtained with electrical stimulation. There seemed to be a non-linear relationship between the amplitude of the response and the depth of skin indentation. The presented data contribute a more detailed picture of epidurally recorded spinal SEPs than previous studies. They will serve as a reference for further analysis of SEPs evoked by stimulation of the affected side in pain patients, to explore whether the painful state is associated with altered SEPs before or after therapeutic intervention.

Adult↗
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

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.

Acoustic Stimulation↗