Brainstem response audiometry in chronic Lyme borreliosis.

Auditory brainstem responses (ABR) were investigated in 26 patients with acrodermatitis chronic atrophicans, which is a late manifestation of Lyme borreliosis. Nine of the patients showed pathological ABR, four of them unilaterally and five bilaterally. The main pathological findings were: 1) Poor reproducibility of waves IV-V or of wave V; 2) Increased latency of wave V. After antibiotic treatment, ABR was improved in eight of the nine patients, and in three of them it was normal. In the five patients who did not completely recover, the improvement consisted in better reproducibility and a tendency towards normal wave V latencies. The results of this study indicate that the central nervous system may become involved in patients with acrodermatitis chronica atrophicans.

Will contralateral white noise interfere with the monaurally click-evoked brainstem response?

Monaurally evoked (and ipsilaterally recorded) ABRs to clicks at 70 dB nHL in the presence of contralateral masking by white noise at 60, 70, 80 and 90 dB HL were compared with the corresponding ABRs without contralateral masking. The investigation was performed in 11 normal, young female subjects. There were no differences concerning wave shape and relative amplitudes, except slight changes in one subject. The following latency findings concern group statistics. The latency of wave I did not change significantly with contralateral noise at any one of the four levels. The latency of wave III was significantly prolonged only at the noise level of 90 dB HL. The latency of wave V was significantly increased at the noise levels of 80 and 90 dB HL. The average latency prolongations were on the order of 0.05 ms. The findings suggest the latency increments to be attributable to central masking rather than to acoustic crossover or stapedius reflex elicitation. Contralateral white noise levels below 80 dB HL would not seem to affect the ABR to clicks above 65 dB nHL.

A case material with post lingual severe hearing loss and communication handicap.

The analyses have given some general clues to the therapeutic handling of these patient categories: 1. The A and B groups can be labelled "hearing" with clearly useful residual hearing. 2. The patients in the C group, as a rule, are utilizing very little from acoustic speech stimulation, mostly the prosodic information. Several patients in this group are possible implant candidates, and it is reasonable to expect that (with a suitable stimulus device and a suitable application of this) the patients could get an additional support during speech reading, so that they function as the B group. Tactile devices are also an alternative or a supplement for this group, and a pilot study on six patients is in progress in the department in cooperation with the Department of Speech Communication at the Royal Institute of Technology. 3. The patients within the A and B groups will in the first place be offered additional functional training programmes (prosodic training, audio-visual training and possibly vibration training) and, as an ultimate alternative a social activation in group therapy may be considered. Some patients in these groups might also be candidates in the future for an extra cochlear implant.

Latencies of ABR (waves III and V) to binaural clicks: effects of interaural time and intensity differences.

Auditory brainstem responses to monaural clicks and to binaural clicks delivered with interaural time differences of 0.5 and 1 ms (delayed clicks in left ear) and interaural intensity differences (right ear minus left ear) of 0, +/- 10, +/- 20, and +/- 30 dB were recorded bilaterally in 7 normal subjects. Latencies of wave III and wave V were studied as functions of click intensity difference for each of the two time-of-onset differences. As the intensity difference was gradually varied from +30 to -30 dB, the latencies were seen to shift (with constant III--V interval) from those of a monaural right-ear (non-delayed clicks) response to those of a monaural left-ear (delayed clicks) response by 0.5 and 1 ms. In all subjects this shift occurred in the 20-dB interval between equal intensity and 20-dB lagging-click dominance, and almost always most of the shift took place in either of the two 10-dB subintervals. Occasionally double-peaked waves appeared in the 20 dB-interval. Binaural ABRs may become useful for diagnosis in patients with signs of brainstem disorder but with normal-hearing and normal audiometric findings including monaural ABR, as such patients have been found to shift their latencies more slowly with varying interaural intensity difference.

Bilaterally recorded auditory brainstem responses to monaural stimulation. Latency and amplitude differences in normal subjects.

Ipsilaterally and contralaterally (forehead-mastoid) recorded ABRs to monaurally administered clicks at 90 dB nHL were compared in 16 young normal-hearing female subjects (32 ears). The comparisons were made with regard to latencies and amplitudes of waves I, III and V, and the results concern group statistics. Wave I was recordable in the contralateral derivation in less than 50% of the cases. The amplitudes of waves I and III were significantly smaller, and the latency of wave III significantly shorter (by an average of 0.15 ms) in the contralaterally recorded ABR. There was a tendency for wave V to diminish and to lag in the contralateral recording; however, there were no statistically significant differences in wave V amplitude and latency between the two sides. Nor was there found to be any significant variability differences concerning wave III and wave V latencies between the two derivations. The dominance of the wave V peak-to-peak amplitude was established in both recordings. Two concluding computations showed that there were no differences between right and left ear stimulation, and no differences between recordings performed with the ground electrode applied to the nasion or to the sternum.