Recurring intracranial meningiomas. Evaluation of some factors predisposing for tumor recurrence

60 cases of recurring meningiomas are analyzed in respect to factors influencing the risk of tumor recurrence. In our series of meningiomas operated on between 1970 and 1980 the recurrence rate was 9.5%. Recurrence rate was highest in tumors of the medial sphenoid. Incomplete tumor resection according to Simpson's grade III and IV lead to a higher recurrence rate than in grade I and II resection, but the difference is statistically not significant. Presence of mitoses, brain invasion and focal necrosis also is linked to a higher tumor recurrence rate. Tumors exhibiting all these three characteristics recurred in every case. Absence of lymphocytic tumor infiltration as a factor of risk is statistically not significant.