A 55-year-old woman comes to the physician due to a 4-month history of progressive hearing loss in her right ear. Vital signs are within normal limits. Inspection of the external ear canals and tympanic membranes shows no abnormalities. Neurologic examination shows decreased hearing in the right ear; hearing in the left ear is normal. MRI of the head with contrast is shown in the image below: Which of the following is the most likely diagnosis?

Question

A 55-year-old woman comes to the physician due to a 4-month history of progressive hearing loss in her right ear.  Vital signs are within normal limits.  Inspection of the external ear canals and tympanic membranes shows no abnormalities.  Neurologic examination shows decreased hearing in the right ear; hearing in the left ear is normal.  MRI of the head with contrast is shown in the image below:  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_39b1_3a68_9249_d745379ec360_MD0001_00 This patient has a homogeneously enhancing, extraaxial tumor at the cerebellopontine angle, leading to compression of the vestibulocochlear nerve (CN VIII) resulting in unilateral, progressive hearing loss. Pathologically, this may be a vestibular schwannoma or a meningioma. Although imaging findings can help differentiate between the two (eg, extension into internal auditory canal [schwannoma], dural enhancement [meningioma]), histologic analysis is often required for definitive diagnosis. Meningiomas are considered benign primary brain tumors arising from meningothelial cells and are more commonly found in middle-aged to elderly women. They can cause significant neurologic symptoms if they become large enough to compress neurovascular structures. Classically, meningiomas at the cerebellopontine angle cause progressive sensorineural hearing loss, tinnitus, and imbalance or disequilibrium. With continued growth, they can cause facial weakness (facial nerve [CN VII]) and facial numbness (trigeminal nerve [CN V]). Treatment is typically surgical resection. Histology shows cells arranged in lobules or whorls, often with psammoma bodies. (Choice A) Arteriovenous malformations are congenital lesions that frequently present with headaches and seizures in children and young adults. On MRI, they often appears as hypointense lesions (due to flow voids) with a honeycomb appearance. (Choice B) Astrocytomas are pediatric CNS tumors that originate from astrocytes (the dominant glial cell in the brain). Because of this, they develop in the brain parenchyma rather than an extraaxial location. (Choice C) Ependymomas arise from the ependymal lining of the ventricles, often from the roof of the fourth ventricle in children or the intramedullary space of the spinal cord in adults. They would not be located in the cerebellopontine angle. In addition, intracranial ependymomas typically present with progressive headaches and signs of increased intracranial pressure due to obstructive hydrocephalus. (Choice D) Medulloblastomas typically present in children (most commonly age 5-9) with vomiting, headache, and cerebellar dysfunction. They are typically located along the cerebellar midline (rather than the cerebellopontine angle) and may compresses the fourth ventricle, causing obstructive hydrocephalus and increased intracranial pressure. Educational objective: Tumors at the cerebellopontine angle can cause unilateral progressive hearing loss due to compression of the vestibulocochlear nerve (CN VIII). These tumors are most likely vestibular schwannomas or meningiomas; histologic analysis is often required to differentiate between them. __________ References: Meningioma: a review of clinicopathological and molecular aspects. (http://www.ncbi.nlm.nih.gov/pubmed/33194703) Cerebellopontine angle masses: radiologic-pathologic correlation. (http://www.ncbi.nlm.nih.gov/pubmed/8210595)

A 55-Year-Old Woman Comes to the Physician Due to a 4-Month