Primary Lymphoma of the Internal Auditory Canal Case Report and Review of the Literature

We report a rare case of a primary intracranial B cell lymphoma originating in the internal auditory canal. The clinical manifestations were indistinguishable from those of other, more common tumors of the same region. We achieved total gross tumor removal with preservation of the facial nerve. A detailed histologic examination and a systemic workup confirmed the primary nature of this tumor. To our knowledge, this is the second case reported in the literature of a primary malignant lymphoma originating in the internal auditory canal. This is the first instance that includes immunohistochemical and cytometric studies of fresh tissue. We discuss the management of primary lymphomas of the central nervous system, with special emphasis on their association with acquired immunodeficiency syndrome and other immune system diseases. Awareness of primary central nervous system lymphomas is important, since a greater occurrence of these rare tumors in the cerebellopontine angle is probable in the future

Auditory Brainstem Implant: I. Issues in Surgical Implantation

Most patients with neurofibromatosis type 2 (NF2) are totally deaf after removal of their bilateral acoustic neuromas. Twenty-five patients with neurofibromatosis type 2 have been implanted with a brainstem electrode during surgery to remove an acoustic neuroma. The electrode is positioned in the lateral recess of the fourth ventricle, adjacent to the cochlear nuclei. The present electrode consists of three platinum plates mounted on a Dacron mesh backing, a design that has been demonstrated to be biocompatible and positionally stable in an animal model. Correct electrode placement depends on accurate identification of anatomic landmarks from the translabyrinthine surgical approach and also on Intrasurglcal electrophysiologic monitoring. Some tumors and their removal can result in significant distortion of the brainstem and surrounding structures. Even in the absence of Identifiable anatomic landmarks, electrode location can be adjusted during surgical placement to find the location that maximizes the auditory evoked response and minimizes activation of other monitored cranial nerves. Stimulation of the electrodes produces auditory sensations in most patients, with results similar to those of single-channel cochlear Implants. A coordinated multldlscipllnary team is essential for successful application of an auditory brainstem implant