title: Uncommon lesions in the internal auditory canal (IAC): review of the literature and case report.
abstract: BACKGROUND
  Despite the relatively frequent occurrence of multiple primary tumors, namely, 10% of intracranial tumors, metastasis is a rare occurrence within the internal auditory canal (IAC) and cerebellopontine angle (CPA). Intracanalicular metastases of adenocarcinoma are documented, but a primary adenocarcinoma remains unreported. We provide a review of uncommon lesions in the IAC and describe to our knowledge the first instance of a primary adenocarcinoma.
  
  
  METHODS
  A 60-year-old man presented with nausea and vomiting. Cranial computed tomography scan revealed bilateral nonspecific periventricular and subcortical vascular lesions. He presented 8 months later with left-sided tinnitus, progressive hearing loss, and attacks of vertigo. Magnetic resonance imaging (MRI) showed an extra-axial mass most likely representing a left-sided vestibular schwannoma with characteristic contrast enhancement in the IAC. The follow-up MRI showed an unchanged pattern of contrast enhancement. Due to progressive headaches and dizziness, the patient underwent a left transtemporal craniotomy with subtotal tumor resection. Histological examination revealed blennogenic cylindrical adenocarcinoma. The investigations for the primary tumor site were all negative. The patient's condition deteriorated gradually. MRI showed an increase of the residual tumor and meningeosis carcinomatosa, and cerebrospinal fluid (CSF) examination was positive for tumor cells. The patient was treated with intrathecal chemotherapy. He died of multiple organ failure.
  
  
  CONCLUSIONS
  The discussion focuses on the incidence of extra-axial CPA and IAC lesions with their clinical presentations and their radiological findings. We address the issue of a possible regulation of CPA lesion laterality by asymmetrically expressed genes. In view of the sparse literature on treatment of single intracanalicular metastases, the review is broadened to the current treatment recommendations of single brain metastases.
  
  
  CONCLUSIONS
  The differentiation between benign and malign lesions in the CPA and IAC is important, as it requires diverse treatment protocols. For the physician this differentiation represents a clinical and radiological challenge. For the developmental research the left-right asymmetry might be a field of research.
authors.affiliation: Department of Voice, Speech and Hearing Disorders, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. a.rohlfs@uke.uni-hamburg.de
authors.forename: Anna-Katharina
authors.initials: AK
authors.lastname: Rohlfs
authors.forename: Ralf
authors.initials: R
authors.lastname: Burger
authors.forename: Christoph
authors.initials: C
authors.lastname: Viebahn
authors.forename: Paul
authors.initials: P
authors.lastname: Held
authors.forename: Matthias
authors.initials: M
authors.lastname: Woenckhaus
authors.forename: Frank W
authors.initials: FW
authors.lastname: Römer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Strutz
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D001932:Brain Neoplasms / Q000473:pathology; D002530:Cerebellopontine Angle / Q000473:pathology / Q000601:surgery; D003399:Craniotomy; D004424:Ear Canal / Q000473:pathology* / Q000601:surgery*; D004428:Ear Neoplasms / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D017809:Fatal Outcome; D019788:Fluorodeoxyglucose F18; D034381:Hearing Loss / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000209:etiology; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D013701:Temporal Bone / Q000601:surgery; D014012:Tinnitus / Q000209:etiology; D014057:Tomography, X-Ray Computed; D014839:Vomiting / Q000209:etiology
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18