[Neurinomas with normal brain stem auditory evoked potentials].

Of 145 neurinomas operated upon, 2% had normal brain stem auditory evoked potentials (BERA). Potentials were obtained by means of a special technique allowing extraction every 600 ms and its follow up with time (brain stem temporal dynamic). This score of 2% was also that reported by some American authors who associate electrocochleography with BERA. The latter provide an accurate diagnosis in 96% of cases of all types of tumors taken together and in 91% of cases of small tumors. Furthermore, the performance of conventional scan imaging is accurate in only 25% of small tumors whereas gas meatocysternography detects more than 95% of cases. The latter method is therefore the most sensitive one but it possesses the disadvantage of being invasive and of costing much more than BERA, which remains therefore the least invasive examination providing the best and earliest diagnosis.