[Clinical and electromyographic features of "intermittent tonic facial spasm" due to acoustic neurinoma. Report of two cases].

The authors report two cases of acoustic neurinoma involving intermittent tonic contractions of the facial muscles on the affected side. The clinical features, and in one case the electromyographic (EMG) findings, were compared to those in cases of hemifacial spasm (HFS) due to neurovascular compression (NVC). Both patients exhibited intermittent facial tonic muscle contractions and deep nasolabial folds on the affected side despite facial weakness. In one case, EMG showed continuous muscle activity not only during contractions but also at rest. On the other hand, in HFS due to NVC, EMG demonstrated intermittent bursts of activity during spasm but little or no activity at rest. In both of these cases the tumor was large enough to compress the brainstem. In neither case could the facial nerve be identified during subtotal tumor removal. These findings suggest that the nature of the facial muscle contractions in these two cases was quite different from that of HFS due to NVC. The former appeared to be an incomplete form of the so-called “continuous tonic facial spasm” attributable to glioma of the brainstem. Such contractions might better be termed “intermittent tonic facial spasm.”