ObjectiveTo investigate the effect of microsurgical therapy and the key techniques in resection of large bilateral olfactory groove meningiomas via unilateral subfrontal approach.MethodsThe clinical data and follow-up results of 181 patients with large bilateral olfactory groove meningiomas who underwent microsurgical removal between June 2007 and May 2014 were retrospectively analyzed. The initial symptom was headache or (and) dizzy in 95 cases, hyposmia or anosmia in 53, impairment of visual function or (and) visual field deficits in 26, cognitive deficits in 3, epilepsy in 2, and accidentally discovered in 2. Unilateral subfrontal approach was applied in all patients (neuroendoscopy was applied in some cases in the later period); incision of falxcerebri, and when necessary, ligation of superior sagittal sinus to resect contralateral tumor were performed. Simultaneous or staged period resection of tumors invading skull base such as ethmoid sinus and superior meatus and reconstruction of the skull base were performed.ResultsThere was no perioperative mortality. Simpson grade Ⅰ resection was obtained in 33 cases, grade Ⅱ resection was in 141, grade Ⅲ resection was in 4, and grade Ⅳ resection was in 3. Among the 229 eyes with preoperative visual impairment, postoperative visual improvement was found in 215 eyes, unimproved was in 12, and aggravation was in 2. The 59 sides which lost their function of olfactory nerve before surgery obtained no recoveries after surgery, while olfactory nerve with residual function preoperative still kept sensing after surgery in 149 lateral sides (149/303). The patients were followed up for (76.9±43.8) months, and postoperative recurrence or residual tumor growth were found in 21 cases.ConclusionsBecause of the contralateral ocular and (or) nasal compensation, early discovery is very difficult for patients with olfactory groove meningioma. The unilateral subfrontal approach can provide sufficient exposure for resection of large bilateral olfactory groove meningiomas and improve the visual acuity and visual field deficits. But it is poor at the preservation of olfactory function. The approach, better with the aid of neuroendoscopy, can improve the total cutting rate, with the advantages of minimally invasion and fewer complications. It is a worthy priority for these tumors.