錐体骨より発生したepidermoid tumorの2例

Epidermoid Tumor Originating from the Petrous Bone: Report of Two Cases

Ⅰ．はじめに

　錐体骨より発生するepidermoid腫瘍は比較的稀な先天的疾患である^3,4,9,10,12)．われわれはその2例を経験したので，画像診断，手術方法につき考察を加え，報告する^1,7,15)．

　In case 1,the tumor was incidentally found in the right petrous bone,middle cranial fossa and cerebello-pontine angle. T1 weighted MRI demonstrated a low intense mass and T2 weighted imaging demonstrated hyperintensity. Through the subtemporal extradural approach,an epidermoid in the middle cranial fossa was partially removed. Postoperative course was uneventfull but an episode of rhinorrhea occurred 15 months later. Bone-window CT scan disclosed air cells of the petrous bone were exposed to the previous surgical cavity. Using the same approach,an epidermoid was totally removed. With the sealing of the tumor cavity with the vascularized muscle flap,the patient became free from rhinorrhea.

　Case 2 had complainted of sensory impairment in the left trigeminal nerve distribution, atrophy of the left temporal and masseter muscle, and diplopia. T1 weighted imaging of MRI demonstrated a low-intense mass in the left petrous bone, middle cranial fossa, temporal lobe, and cerebello-pontine angle, and T2 weighted imaging demonstrated hyperintensity. The intradural tumor under the temporal lobe was removed at another hospital. As the diplopia deteriorated 5 years later, the patient was re-introduced to our hospital. At first, the tumor in the cerebello-pontine angle was removed using the left retromastoid lateral suboccipital approach. Later, the tumor in the petrous bone and middle cranial fossa was removed through the left subtemporal extradural approach. With the sealing of the tumor cavity with the vascularized muscle flap, postoperative cerebrospinal fluid leakage was prevented.

　The epidermoid tumor in the petrous apex is a congenital and rare disease. The obstruction of the petrous air cell and dural defect using the vascularized flap is most important to prevent postoperative cerebrospinal fluid leakage.