Acute sensorineural hearing loss resulting from cerebellopontine angle arachnoid cyst

We present the case of a 49-year-old woman who presented with acute, nonprogressive left sensorineural hearing loss and benign positional vertigo that was associated with an arachnoid cyst of the cerebellopontine angle. The presence of the lesion was documented by MRI examinations that were obtained 7 years apart. Arachnoid cysts at the cerebellopontine angle are usually found incidentally on MRI performed for unrelated reasons. However, if the arachnoid cyst displaces or compresses adjacent cranial nerves, symptoms may result. We review the salient imaging features of arachnoid cysts that allow their differentiation from other lesions of the cerebellopontine angle.