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Sudden unilateral hearing loss and vascular loop in the internal auditory canal: case report and review of literature
Shayan Moosa, Francis Fezeu, Bradley W. Kesser, Arjun Ramesh and Jason P. Sheehan

Disclosures/Conflicts of Interest/Funding: None

Objective: We present a patient with unilateral sudden sensorineural hearing loss (SSNHL) who was found to have a vascular loop in the ipsilateral internal auditory canal (IAC), and we review the literature regarding this association. Underlying pathophysiologic factors surrounding microvascular compression of the vestibulocochlear nerve are poorly understood and make treatment recommendations, especially the option of microvascular decompression, difficult if not controversial. The current report represents an attempt to understand this clinical entity as discussed in the current literature.

Case summary: A 77-year-old female with a long history of progressive right-sided hearing loss and episodic vertigo developed unilateral right SSNHL, tinnitus, vertigo, and disequilibrium. She was originally diagnosed with a vestibular schwannoma on magnetic resonance imaging (MRI) and was referred to our institution for Gamma Knife radiosurgery. Repeat MRI demonstrated a loop of the anterior inferior cerebellar artery (AICA) compressing the vestibulocochlear nerve within the right IAC. There was no evidence of a schwannoma on the repeat MRI. She was not offered radiosurgery, and she elected conservative management.

Conclusion: Vascular compression of cranial nerves can lead to neuronal dysfunction, and this has been rarely described in patients involving the vestibulocochlear nerve complex. There is evidence that microvascular decompression (MVD) of the vestibulocochlear nerve can be effective in selected patients who exhibit pulsatile tinnitus or disabling positional vertigo in the setting of a vascular loop within the ipsilateral IAC, but available evidence at this time does not support MVD for SSNHL.

Keywords: Hearing loss, Internal auditory canal, Cerebellopontine angle, Vessel loop, Anterior inferior cerebellar artery, Vascular malformation, Vestibular schwannoma, Microvascular decompression, Magnetic resonance imaging

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