Anatomical analysis of offending vessels for hemifacial spasm and the surgical results of microvascular decompression

Objective To analyze the anatomical relationship between the offending vessels of hemifacial spasm(HFS)and the facial nerve and to provide an anatomical basis for microvascular decompression(MVD)in patients with HFS.Methods The clinical data of 106 patients with HFS treated with MVD from January 2003 to August 2007 were analyzed retrospectively.All patients underwent 3D-TOF-MRA before the operation in order to find out whether the offending vessels existed or not and their origin and running course.During the operation,the root exit zone(REZ)of facial nerve was exposed through the suboccipital retrosigmoid-inferiolateral cerebellum approach.After carefully observing the offending vessels and their origin,a Teflon graft was inserted between the vessels and root exit zone of the facial nerve near the brainstem.Results 3D-TOF-MRA revealed that the positive rate of microvascular compression of facial nerve was 92%.The specific microvascular compression was found in all patients during the operation,and the anterior inferior cerebellar artery accounted for 66%(70/106)in the offending vessels.Apparente vascular impressions were found on the facial nerve at the REZ in 34 patients.The spasm resolved completely immediately after the operation in 104 patients,and the symptoms of spasm improved significantly in 2 patients,and they were cured in three months.The total effective rate was 100%.Conclusions Vascular compression may be the main cause of HFS.Exposing REZ during operation,accurately identifying the offending vessels,fully decompressing of REZ,the size of graft,and location of graft placed are the important factors of influencing surgical efficacy.Skillful microsurgical technique and accurately identifying the offending vessels during the operation,as well as properly decompressing facial nerve are the key factors in improving surgical efficacy and reducing the recurrence of symptoms.