Biomedical subjects
T Hoeppner
Publications and source records attributed to T Hoeppner.
Application of phase spectral analysis for brain stem auditory evoked potential detection in normal subjects and patients with posterior fossa tumors.
A statistical test of the brain stem auditory-evoked potential (BAEP) detection is presented. The data were collected by averaging groups of 200 sweeps in order to obtain a set of group averages. The synchrony measure (SM), which represents the degree of reproducibility for group averages, is used as a statistical measure and is calculated from the phase variance for selected Fourier components of the group averages. The sensitivity of the test was demonstrated on 375 normal BAEPs with different stimulus intensities (45, 60, 75 dB SL) from both the ipsilateral and contralateral recordings, and on 82 BAEP recordings in the absence of stimulus. In all 375 cases of normal BAEPs the SM exceeds the threshold level while in the absence of stimulation the SM was below the threshold level. The clinical usefulness of the test was demonstrated on 22 patients with tumors of the posterior fossa. The absence of the BAEP was detected in 21 patients. In 12 out of 13 patients with lateralized tumors (acoustic neuromas), absence of the BAEP was noted for stimulation of the affected ear.
Visual evoked responses and visual symptoms in multiple sclerosis.
Absolute latency, interocular difference in latency, and waveform of visual evoked responses (VER) to checkerboard reversal stimuli recorded from the midline of the skull were studied in 104 multiple sclerosis patients, 25 to 50 years of age, classified according to visual symptomatology. Group 1 had strong evidence of past or present optic neuritis. Patients with blurring of vision, diplopia, and undefined visual complaints were assigned to group 2, while group 3 contained patients with no visual symptoms but suspected diagnosis of multiple sclerosis on other grounds. The three parameters explored showed consistent association with the degree of visual involvement, as assessed by clinical impression, but their discriminatory power was diverse. Absolute latency was significantly longer in group 1 patients compared with groups 2 and 3, but it did not discriminate between the last two, whereas interocular difference in latency proved to be sensitive to differences between symptomatic (diplopia, blurring) and asymptomatic groups (2 and 3). Waveshapes were grouped into three categories based upon degree of distortion of the major positive peak, and their relative distribution among the three patient groups was found to be associated with symptomatology. We suggest that, in the production of symptoms such as diplopia, a temporal disparity of afferent impulses might be involved in much the same way that spatial incongruities between both eyes lead to impaired function. In this regard, interocular difference in latency rather than absolute latency would be a more accurate predictor of symptom development. The analysis of VER waveshape suggests, in addition, the importance of inhomogeneous involvement of the visual pathways in the production of symptoms during the evolution of multiple sclerosis.
[Checkerboard-reversal evoked potential and visual symptomatology in multiple sclerosis (author's transl)].
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Brainstem auditory evoked response (BAER): Clinical perspectives and normative data.
Research pertaining to the physiological mechanisms involved in the generation of brainstem auditory evoked responses is reviewed emphasizing the current status of its clinical applications, pointing out present gaps in knowledge and delineating avenues for further inquiry. Some work conducted in our laboratory aimed at statistical description of BAER parameters relevant to clinical practice is presented, along with assessment procedures that are deemed promising for routine work. Relevant implementation procedures are described.
Letter: Trophic effects of striatal neuron denervation.
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The effect of mosaic colour filters (Piringer lenses) on the ERG of patients with normal colour vision.
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