A 63-year-old woman presents for workup to determine the reason for a gradual hearing loss over approximately 5 years and intermittent tinnitus over the last several months. Findings on physical and neurologic examination are entirely within normal limits, except for the presence of sensorineural hearing loss in the left ear. She has no cranial nerve deficits. An MRI of the brain with gadolinium reveals the presence of an extra-axial tumor in the region of the left cerebella-pontine angle. What is the most likely diagnosis?
High-Yield Explanation
This cerebella-pontine angle tumor is most likely an acoustic neuroma. This is the most commonly encountered neoplasm in this region. It arises from the Schwann cells that form the myelin sheath of the vestibular division of the eighth cranial nerve (hence a more accurate name is vestibular schwannoma). This tumor typically arises within the internal acoustic canal and growths in the direction of least resistance - through the meatus into the cerebellopontine angle cistern.