• Audrey P Calzada, John L Go, Donald L Tschirhart, Derald E Brackmann, and Marc S Schwartz.
• *House Ear Clinic, †Department of Radiology, University of Southern California; ‡Department of Pathology, St. Vincent Medical Center; and §House Clinic, Neurosurgery, Los Angeles, California, U.S.A.
• Otol. Neurotol. 2015 Mar 1; 36 (3): 491-7.

ObjectiveTo describe the clinical and radiographic characteristics in a series of patients with non-vestibular schwannoma cerebellopontine angle (CPA) and intracanalicular (IAC) masses, who underwent microsurgery for presumed vestibular schwannoma (VS).Study DesignRetrospective case series.SettingTertiary neurotologic referral center.PatientsOne thousand five hundred ninety-three patients underwent microsurgery for apparent VS from 2002 to 2013. Of these, 53 patients (3%) were discovered to have a diagnosis other than VS.InterventionsMiddle fossa, translabyrinthine, and retrosigmoid craniotomy.Main Outcome MeasuresClinical presentation, radiologic analysis, and histopathology examination.ResultsThere were 17 facial schwannomas, 15 meningiomas, 9 hemangiomas, 6 lipochoristomas, 3 inflammatory reactions, and one each of lymphoma, glial heterotopia, solitary fibrous tumor, ependymoma, and a non-diagnostic mass. Excluding facial schwannomas, 23 cases were misdiagnosed as VS in the first half of the study period, compared to only 15 cases in the latter half (p = 0.09). Ninety-six percent of patients presented with some combination of sensorineural hearing loss, balance disturbance, and tinnitus. In the subset of patients with available preoperative MRI scans for retrospective review, only 4 of 28 patients had radiologic findings suggestive of pathology other than VS. The most common missed radiologic diagnoses were facial schwannoma, lipochoristoma, and meningioma.ConclusionA subgroup of patients with CPA and IAC masses who present with radiologic findings diagnostic of VS will have an alternative histopathologic diagnosis. Optimal radiologic imaging and experienced interpretation can improve diagnostic accuracy. The most common tumors that mimic VS despite ideal radiologic imaging are facial schwannomas, meningiomas, and hemangiomas.

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