Background: Anterior inferior cerebellar artery (AICA) aneurysms in the internal auditory canal (IAC) are rare. We have reported a case of dissecting AICA aneurysm in the IAC presenting initially with the eighth nerve palsy followed by the seventh nerve palsy without hemorrhage. Case Description: A 68-year-old woman presented with a sudden onset of vertigo accompanied by deafness and tinnitus on the right side that was preceded by intermittent right retroauricular pain 2 weeks before. Audiogram showed severe sensorineural hearing loss. Computed tomography and magnetic resonance imaging (MRI) indicated absence of prior subarachnoid hemorrhage. Magnetic resonance angiogram (MRA) suggested a tiny aneurysm at the fundus of the IAC accompanied with thinning of the lateral pontine segment of the AICA. Conservative treatment led to moderate improvement of the symptoms. However, the patient developed the right retroauricular pain again, followed by the right facial paralysis 5 months later but still without signs of hemorrhage on MRI. Digital subtraction angiogram showed dissecting aneurysm in the IAC. The patient was managed with oral steroids and direct intervention was avoided due to a risk of ischemia supposed by large area irrigated by the AICA. Follow-up MRA 18 months after the first presentation showed improvement in the narrowing of the AICA proximal to the aneurysm. The patient was functionally independent despite right-sided hearing loss and slight facial paresis. Conclusion: This report warns physicians that a dissecting AICA aneurysm without subarachnoid hemorrhage may cause eighth and seventh nerve palsy.
