Yonago Acta medica 2008;51:101–106

Endolymphatic sac tumors are rare low malignant neoplasms of the petrous temporal bone, with symptoms referable to auditory, vestibular or facial nerves, which should be strictly discriminated from benign tumors of the temporal bone. Differential diagno-sis between both at the early stages of checkup controls the treatment and prognosis. Complete surgical resection is the treatment of choice, which commonly provides long-term control. We have experienced a 48-year-old man with progressive hearing loss, un-steadiness and constant tinnitus. Computed tomography and magnetic resonance imag-ing (MRI) demonstrated a tumor invading the posterior petrous bone, extending to the posterior fossa. In the course of image diagnosis of his disease, we observed diagnostic efficacy of 3-tesla MRI, which showed excellent lesion visualization even in a small-size endolymphatic sac tumor. The intraoperative pathologic diagnosis was not available. Key words: endolymphatic sac tumor; pathologic diagnosis; temporal bone surgery; 3-tesla magnetic resonance imaging Endolymphatic sac tumors, rare lesions of the petrous temporal bone, arise in the vicinity of th