Histological acoustic tumor involvement of the VIIth nerve and multicentric origin in the VIIIth nerve.

The surgical plane between the VIIth nerve and acoustic tumor is often elusive. This histological relationship was reviewed in three patients who underwent VII-VII neuroanastomosis at tumor removal disclosing an inseparable surgical plane in two. In the third patient, tissue sections did not accurately show the relationship. In all three, surgical planes were not apparent at tumor removal. Another patient had a second, isolated tumor in the same VIIIth nerve proximally at the brain stem root entry zone. This was seen only on permanent section. In considering "total" tumor removal by microsurgical standards, these histological findings should be kept in mind. We advocate removal of the entire VIIIth nerve to the brain stem root entry zone along with smaller tumors.