Hemifacial spasm can be the presenting symptom of a fourth ventricle tumour. A short case-illustrated review and pathogenetic considerations.

In this short case-illustrated review we aimed to analyse the possible nuances of hemifacial spasm (HFS) as the presenting symptom of a tumour of the fourth ventricle. The issue is remarkable since HFS can be secondary to a fourth ventricle tumour, even when no other neurological signs are reported. In addition, the possible presentation with only upper facial muscle involvement, as in the presented case, can be deceitful because this is characteristic of the benign and much more frequent "typical" form. Based on our intra-operative data and on the previously reported cases, we think that pathogenesis could be referable to the facial nerve nucleus involvement and that clinical nuances could be related to the specific somatotropy of the nucleus under the fourth ventricle floor that, as in our case, can be infiltrated by tumour. Resolution of the disorder can usually be obtained after the complete resection of the tumour that in the reported case resulted a subependymoma (WHO grade I), so far never described in literature associated with HFS.