8 This review of all 84 documented cases of lipomas of the IAC/CPA showed that although surgical resection had been performed in 62%, total tumor resection was accomplished in only 17 of 52. The clinical observation that these tumors are intimately associated with the auditory nerve was reported by Bigelow et al in 1998. 3 As such, they were classically and still are often erroneously referred to as “lipomas” of the IAC/CPA. Lipochoristomas (lipomatous choristomas) classically were thought to arise from cells of the meninx primitiva, the mesenchymal derivative of the neural crest, which underwent abnormal differentiation. Lipochoristoma of the internal auditory canal (IAC). She is currently considering a bone-anchored hearing aid. The patient remains symptomatically stable with improved equilibrium but persistent left-sided hearing loss. Conservative management was recommended, and on 17-month follow-up there has been no interval growth. With fat-suppressed images, there was no enhancement of the lesion, and the diagnosis of IAC lipochoristoma was confirmed. It was recommended that the patient undergo an interval MRI with gadolinium. An MRI obtained at an outside institution was read as a “small enhancing intracanalicular acoustic neuroma on the left.” Initial review of this MRI demonstrated a small (5 × 4 mm) T1 hyperintense lobulated lesion in the distal IAC. Her initial audiogram demonstrated a left-sided severe sensorineural hearing loss with a word recognition score of 30% her right ear demonstrated normal hearing. In addition, the patient reported chronic headaches and intermittent ipsilateral facial paresthesias. In this report we examine the appropriate work-up, diagnosis, and management of lipochoristoma of the IAC/CPA.Ī 51-year-old woman presented with 1 year of progressive left-sided severe hearing loss accompanied by tinnitus and weekly episodes of mild vertigo. Patients with lipochoristomas may present with hearing loss, vestibular symptoms, or tinnitus. 4 This theory offers an explanation for the failure of hearing conservation reported after surgical resection of these lesions. However, research has since shown that these tumors arise from mesenchyme endogenous to the vestibulocochlear nerve and thus are more appropriately characterized as lipomatous choristomas. Classically, these tumors were thought to arise from cells of the meninx primitiva, the mesenchymal derivative of the neural crest, and thus they were referred to as lipomas of the IAC/CPA. These rare tumors of the CPA and IAC are slow growing and often discovered incidentally. Lipochoristomas (lipomatous choristomas) comprise 0.1% of all CPA tumors. Each of these lesions has typical imaging characteristics that frequently allow a diagnosis to be made with magnetic resonance imaging (MRI) scan alone. 1 2 3 Rare tumors include epidermoids, lipochoristomas, and metastatic tumors. Vestibular schwannoma represents the most common lesion in the IAC (80–90%) with meningiomas comprising nearly all the rest (10%) of IAC tumors. Neoplasms arising within the internal acoustic canal (IAC) and cerebellopontine angle (CPA) are most commonly of neuroepithelial origin. Surgical treatment is reserved for growing lesions or those with disabling vestibular symptoms. Because lipochoristomas may have a tendency for more indolent growth and intimate involvement of the auditory nerve, conservative management with interval imaging is recommended. Fat-suppressed MRI sequences aid in a definitive diagnosis of lipochoristomas. The patient remains symptomatically stable with improved equilibrium but persistent left-sided hearing loss.Ĭonclusions Differential diagnosis of an enhancing lesion in the IAC includes acoustic neuroma, meningioma, epidermoid and arachnoid cysts, lipochoristoma, and metastatic tumors. Conservative management was recommended, and on 17-month follow-up there was no interval growth. A diagnosis of IAC lipochoristoma was made. With fat-suppressed images, there was no enhancement of the lesion. Magnetic resonance imaging (MRI) demonstrated a small (5 × 4 mm) T1 hyperintense lobulated lesion in the distal internal auditory canal. Results (Case Report) A 51-year-old woman presented with left-sided severe hearing loss, tinnitus, mild episodic vertigo, and facial paresthesias progressive over 1 year. Study Design and Methods Retrospective case review. We describe a lipochoristoma of the internal auditory canal (IAC) and present the salient features of the evaluation, diagnosis, and management. Objective Lipochoristomas comprise 0.1% of all cerebellopontine angle tumors and may be misdiagnosed as vestibular schwannomas.
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