[Acoustic neurinomas with large cystic components: a clinical and pathological study of 3 cases].

Acoustic neurinomas containing cystic parts are fairly common, but it is extremely rare for acoustic neurinomas to be mainly composed of cysts. So far, we have encountered three such cases. We studied these cases retrospectively to correlate their characteristic clinical symptoms and their respective pathological findings. Referring to reviews of the relevant literature and our three cases, we would like to discuss the possible mechanism of cyst formation and clinical symptoms. Compared with the patients with ordinary acoustic neurinomas, the patients in our three cases and in some cases in the literature have some distinct and possibly common clinical features. First of all, in spite of the cysts being large, hearing loss was less severe. Secondly, sudden onset of headache and hearing loss were frequently experienced, probably due to intratumoral hemorrhages. Thirdly, intratumoral hemorrhages with niveau formations were frequently able to be identified on CT or MRI scannings. Histologically, our three cases revealed lots of abnormal sinusoid or telangiectasis vessels. Small hemorrhages, hemosiderin deposits and hemosiderin-containing phagocytes were also more abundant than in solid-type neurinomas. The exact mechanism of the formation of these cysts is still controversial. Our hypotheses concerning the probable causes of cyst formation are presented in this study. In our three cases. the most distinct finding was the presence of abundant abnormal sinusoid or telangiectasis-like vessels. We suggest therefore that, in these cases, repeated small hemorrhages from these abnormal vessels, along with subsequent intratumoral changes, are the most probable cause of the formation of these cysts.