Extended middle cranial fossa extradural approach to dumbbell shaped trigeminal neurinomas using the petrous window

Abstract

Objective To evaluate extended middle cranial fossa extradural approach using the Petrous Window for surgery on dumbbell shaped neurinomas.Method During 4 year period between 2007 and 2010,consecutive 21 cases of dumbbell shaped trigeminal neurinomas were treated through extended middle cranial fossa extradural approach using the petrous window.The configuration of the tumor mass was assessed on MRI and CT by measuring its long diameter in the middle and posterior fossa and the width of petrous erosion.Tumors were then classified into three types based on their distribution over the petrous ridge( Mp type =12;MP type =7 and mP type =2).Results Total removal was achieved in 19 patients,subtotally removed in 2.No patient dead of the surgery.A new dysfunction of cranial nerve was observed in 4 patients.The postoperative cerebrospinal fluid leakage was found in 1 case,which was cured by lumbar drainage.After a mean follow - up of 22.4 months (6 -36 months) for 18 patients,16 cases showed no evidence of tumor recurrence and 2 patients with a subtotal removal developed a recurrence after surgery,in the posterior fossa,which was cured by retrosigmoid approach.Conclusion The extended middle cranial fossa extradural approach using the Petrous Window could be an effective method for removing dumbbell shaped trigeminal schwannoma,particularly in cases of wide petrous erosion from the tumor.However,the tumor has a larger posterior fossa components,this approach may not provide adequate exposure to achieve a total resecction. Key words: Dumbbell shaped trigeminal schwannoma; Extended middle cranial fossa extradural approach; Petrous window