Recurrence of intracranial meningiomas: the role played by regional multicentricity. Part 2: Clinical and radiological aspects.

Globular single meningiomas are generally regarded as benign tumors that can be completely removed. Nevertheless, after a total macroscopic resection including the insertion zone (Grade 1 operation according to Simpson's classification), the incidence of recurrence ranged from 9% to 14% at the 5-year follow-up review. The authors have shown that single meningiomas represent only the visible predominant growth in the midst of a wide neoplastic field in the dura mater. Regional multiplicity in meningiomas would thus seem to be the rule. With this in mind, the authors propose to divide recurrences after Grade 1 operations into true local and false regional. A local recurrence is defined as a regrowth within the limits of the previous dural flap. Regional recurrence is when new growth develops outside the previous craniotomy site; this should not be considered as a recurrence but as a new primary site. These regional recurrences might explain some unexpected late tumor growth occurring after a Grade 1 operation. Five illustrative cases in which regional recurrence was detected by computerized tomography are presented. The authors also propose to add a supplementary grade to Simpson's surgical grading: Grade 0. This operation would entail a wide resection of the dura around the attachment zone of the meningioma. The authors hope that with a Grade 0 operation the incidence of recurrence might be reduced.