[Acoustic neuroma. Apropos of a series of 40 cases]

The authors present statistics of 40 acoustic neuromas operated upon by micro-surgical technique in co-operation with oto-neuro-surgery. As regards clinical picture, all persons presenting with unilateral progressive sensoryneural deafness should be subjected to cochlear vestibular and radiologic examination. They advocated essentially two routes:--translabyrinthine approach for the tumours within the internal auditory meatus, --posterior fossa approach for the other tumours. They reported their results and analysed the major advantages of the microsurgical technique which diminish considerably the risk of this surgery, so that the functional result should be of first importance.

Testing for "recruitment" by electrocochleography. Preliminary results

Normal electrocochleographic (E.Co.G.) tracings were compared with those showing characteristics which resemble audiometric recruitment. The normal E.Co.G. shows two major features as click levels are raised: 1) Over the intensity range from 0–80 dB H.L., for the click, the VIII nerve action potential (AP) latency decreases from approximately 4 to 1.5 msec; and 2) at low click levels, the AP wave-form is diphasic, and shows a slow growth with increasing intensity, while at higher levels, the AP wave-form is monophasic and increases more rapidly with increases in sound level. Yoshie has referred to the low and high intensity portions of the AP amplitude curve as the L and H curves, respectively. In patients showing the “recruiting responses”, the threshold for the click is elevated and the latency is reduced at threshold. The wave-form of AP is diphasic over the entire intensity range, and AP amplitude grows much more rapidly than in the normal case. It appears that these “recruiting” responses represent the H curve of Yoshie with the L curve removed. The differences between normal and “recruiting” E.Co.G. responses can be given a tentative interpretation based on current findings on the structure and function of the peripheral auditory receptor.