Auditory field reduction in human following head trauma

Abstract

We measured the tonal auditory threshold for 500, 2000 and 4000 Hz, and made BAER recordings for both ears with unfiltered 125 dB SPL clicks, with 40 subjects between 18 and 23 years of age, 20 subjects having suffered minor cranial trauma during the preceding 48 hours and 20 being control subjects matched for age and sex.

Compared to the control group, trauma patients showed a significantly higher auditory threshold: 19 dB SPL at 500 Hz, 9 dB SPL at 2000 and 4000 Hz. This threshold rise was bilateral.

The head trauma patients showed, on average, one significantly earlier BAER wave I than did controls. This alteration was likewise bilateral.

The latencies of waves II, III and V, the I-III, III-V, and I-V intervals, and the interaural wave latency and interval differences are comparable for trauma patients and control subjects. One to eight months after cranial trauma, 7 subjects manifested one sign of the subjective cranial trauma syndrome. Auditory threshold and BAER wave I earliness were not any greater for these subjects.

Trauma patients seemed to show a reduction of the auditory field. They were hypersensitive to high stimulus intensities (shortening of BAER wave I) and less sensitive to low intensities (rise in tonal auditory threshold). This auditory alteration was bilateral. It can thus be thought that the trauma acts on the central nervous system to affect the operation of the cochlea via efferent pathways.