title: High rate of bilaterality in internal auditory canal metastases.
abstract: OBJECTIVE
  Presentation of three cases of metastatic carcinoma to the internal auditory canal bilaterally, as well as a systematic review of the literature regarding the characteristics of these lesions.
  
  
  METHODS
  Using a MEDLINE Ovid search (1946-2015), we identified and reviewed 102 cases of metastatic carcinoma to the internal auditory canal. Metrics recorded include: patient age, sex, tumor type, laterality, past oncologic history, co-occurring metastatic sites, clinical findings, radiographic findings, therapy received, and outcome. Cases of unilateral versus bilateral IAC were compared.
  
  
  RESULTS
  Remarkably, 52.9% reported cases of internal auditory canal metastases have bilateral occurrence. The most common primary tumor sites for internal auditory canal metastases were lung (21.2%), skin (18.6%), and breast (16.7%), with lung and skin cancers having the highest rates of bilateral metastasis. Meningeal metastasis occurred at a much higher rate in bilateral cases (47.2%) versus unilateral cases (8.5%). Brain parenchymal metastasis also occurred at a higher rate in bilateral cases (38.2%) versus unilateral cases (19.2%). Outcomes for cases of internal auditory canal metastases are generally poor, with 56.3% of unilateral cases and 86.1% of bilateral cases reporting patient death within 5 years from diagnosis.
  
  
  CONCLUSIONS
  In cases of internal auditory canal metastasis, clinicians should carefully assess for not only contralateral disease but also additional metastatic disease of the central nervous system. Rapid-onset hearing loss, tinnitus, vertigo, or facial palsy should raise suspicion for internal auditory canal metastasis, particularly in patients with a known oncologic history.
authors.affiliation: Yale University School of Medicine, Section of Otolaryngology, 800 Howard Ave, 4th Fl, New Haven, CT. Electronic address: michael.t.chang@yale.edu.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Chang
authors.affiliation: Yale University School of Medicine, Section of Otolaryngology, 800 Howard Ave, 4th Fl, New Haven, CT. Electronic address: elias.michaelides@yale.edu.
authors.forename: Elias M
authors.initials: EM
authors.lastname: Michaelides
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary; D000368:Aged; D004428:Ear Neoplasms / Q000556:secondary*; D007758:Ear, Inner / Q000473:pathology*; D006312:Hearing Loss, Bilateral / Q000209:etiology; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D008297:Male; D008545:Melanoma / Q000473:pathology / Q000556:secondary; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000473:pathology; D012878:Skin Neoplasms / Q000473:pathology; D014012:Tinnitus / Q000209:etiology