Importance of preserved periosteum around jugular foramen neurinomas for functional outcome of lower cranial nerves: anatomic and clinical studies.

BACKGROUND Surgical removal of jugular foramen (JF) neurinomas remains controversial because of their radicality in relation to periosteal sheath structures. OBJECTIVE To clarify the particular meningeal structures of the JF with the aim of helping to eliminate surgical complications of the lower cranial nerves (LCNs). METHODS We sectioned 6 JFs and examined histological sections using Masson trichrome stain. A consecutive series of 25 patients with JF neurinomas was also analyzed, and the MIB-1 index of each excised tumor was determined. RESULTS In the JF, meningeal dura disappeared at the nerve entrance, forming a jugular pocket. JF neurinomas were classified into 4 types: subarachnoid (type A by the Samii classification), foraminal (type B), epidural (type C), and episubdural (type D). After an average follow-up of 9.2 years, tumors recurred in 9 cases (36%). Type A tumors did not show regrowth, unlike type B tumors, in which all recurred. Radical surgery by the modified Fisch approach did not contribute to tumor radicality in type C and D tumors, even in cases in which LCN function was sacrificed. In preserved periosteum, postoperative LCN deterioration was decreased. Bivariate correlation analysis revealed that jugular pocket extension, tumor removal, MIB-1 greater than 3%, and reoperation or gamma knife use were significant recurrence factors. CONCLUSION For LCN preservation, the periosteal layer covering the cranial nerves must be left intact except in patients with a subarachnoid tumor. To prevent tumor regrowth, postoperative gamma knife treatment is recommended in tumors with an MIB-1 greater than 3%.