ObjectiveTo analyse the microsurgical treatment and facial nerve preservation of giant acoustic neuromas. MethodsUnder the conditions of facial nerve monitoring, 400 patients with giant acoustic neuromas underwent microsurgical removal via suboccipital retrosigmoid approach between January 2005 and January 2013. There were 186 males and 214 females, with the age ranged from 15 to 74 years (mean, 41.6 years). The disease duration was 2-13 years (mean, 2.4 years). The lesions were located at the left cerebellopontine angle region (CPA) in 191 cases, right CPA in 200 cases, bilateral CPA in 9 cases. The clinical manifestations included unilateral hearing loss and tinnitus as first symptoms in 389 cases, facial numbness in 373 cases, unilateral facial paralysis in 370 cases, headache in 269 cases, lower cranial nerve symptoms with drinking cough and dysphagia in 317 cases, and unstable gait in 342 cases. Preoperative skull base thin layer CT showed varying degrees of horn-like expansion in ipsilateral internal auditory canal opening. MRI showed cysts in 78 cases and solid masses in 322 cases; with hydrocephalus in 269 cases. Postoperative cranial MRI or CT was taken to observe the extent of tumor resection. The preservation of facial nerves in anatomy was assessed by intraoperative microscope video and electrophysiological monitoring; the facial nerves function was assessed according to House-Brackmann (HB) classification on the first day after operation; and the rehabilitation of facial nerve function was also assessed at discharge and at 1 year postoperatively by using HB grade. ResultsTotal tumor removal was achieved in 372 cases (93.00%), and subtotal removal in 28 cases (7.00%). One case died of delayed brainstem ischemia at 14 days after operation, and 1 case died of lung infection at 20 days after operation; 398 cases were followed up 6 months to 8 years (mean, 3.5 years). Recurrence occurred in 1 case because of neurofibromatosis at 5 years after operation. The rate of anatomical preservation of the facial nerve during operation was 91.75% (367/400), and the functional preservation rate at the first day after operation was 62.75% (251/400). The HB grade of facial nerve function showed significant difference aomng 3 time points (at the first day, at discharge and at 1 year after operation) (χ2=23.432, P=0.000). Complications included postoperative intracranial infection in 11 cases (2.75%), cerebrospinal fluid leakage in 29 cases (7.25%), aggravated lower cranial nerve symptoms in 18 cases (4.50%), subcutaneous effusion in 13 cases (3.25%), second operation to remove hematoma in 9 cases (2.25%), postoperative circumoral herpes simplex virus infection in 25 cases (6.25%), and all complications were cured after symptomatic treatment. Postoperative hydrocephalus disappeared in 261 cases. ConclusionSurgical operation is the first choice in the treatment of giant acoustic neuromas. Under the auxiliary of neural electrophysiological monitoring, the microsurgery operation via suboccipital retrosigmoid approach for giant acoustic neuromas has extremely low mortality and high preservation rate of facial nerve function.