ObjectiveTo analyze the advantages in safety and precision of biopsies of the petrous apex and petroclival region using open magnetic resonance imaging (MRI).SettingThe University of Leipzig Medical Center.PatientsBiopsies were taken in 13 patients with tumors of the petrous apex and petroclival region.InterventionWith the patient in the 0.5-T intraoperative MRI system (Signa SP; General Electric Medical Systems, Boston, MA, U.S.A.), biopsies were taken from the petrous apex and the petroclival region under imaging control by transseptal, transsphenoidal access. The region of interest was approached with a virtual pointer (Flashpoint Position Encoder; Image Guided Technologies, U.S.A.) and marked with a gadolinium-filled pointer.ResultsIn all patients, the authors obtained enough tissue for histologic study, which also proved to be the suspected tumor. One patient had a bone cyst, another had a malignant lymphoma, and another two a cholesterol granuloma originating from the petrous apex. Three other patients had metastases (carcinoma of the breast, bronchial carcinoma, and unknown origin). Three patients had a meningioma, and another three a chordoma. The authors did not see any postoperative complications.ConclusionsIn the authors' experience, the transsphenoidal access is favorable for approaching and sampling lesions of the petrous apex and the petroclival region. This route, however, is disadvantageous because the course of the internal carotid artery and the brainstem narrow the surgical space to the petrous apex. Open MRI in these cases is very useful because it allows a safe approach to the tumor by navigation and by visualizing the anatomic structures in real-time imaging.