Acoustic neuroma (schwannoma)

00:00 / 00:00



Acoustic neuroma (schwannoma)

Nervous system


Acoustic neuroma (schwannoma)


0 / 12 complete

USMLE® Step 1 questions

0 / 3 complete

High Yield Notes

6 pages


Acoustic neuroma (schwannoma)

of complete


USMLE® Step 1 style questions USMLE

of complete

A 19-year-old man comes to the clinic due to a feeling of unsteadiness over the past few months. At first, the patient felt more clumsy and often bumped into furniture around the house. More recently, he has been feeling wobbly and often loses his balance. Additionally, the patient states that over this same time period, he needs to raise the volume on the television in order to hear it better. He denies any trauma and does not use tobacco, alcohol, or illicit drugs. Family history is unremarkable. Vitals are within normal limits. On physical examination, the patient has difficulty standing with the feet together and almost falls. He is unable to hear whispering voices bilaterally. An MRI is obtained and shows a 2 cm lesion at the right cerebellopontine angle and a 3.5 cm lesion at the left cerebellopontine angle. This patient is at risk for developing which of the following?  

External References

First Aid








Acoustic schwannomas p. 719

Bilateral acoustic schwannomas p. 719

Schwannomas p. 509, 543, 731

Vestibular schwannomas p. 543

External Links


Schwannoma, sometimes called neurilemmoma, is a tumor that develops from Schwann cells.

Schwann cells belong to a category of cells called glial cells, which surround and support the neurons of the nervous system, and get their name from Theodor Schwann, a nineteenth-century physicist who first discovered them.

Neurons are made up of three main parts.

The dendrites, which are little branches off of the neuron that receive signals, which is essentially an electrical impulse, from other neurons; the soma, or cell body, which has all of the neuron’s main organelles like the nucleus; and the long axon, which transmits the signal to the next neuron in the series.

In the peripheral nervous system, Schwann cells synthesize a fatty substance made of lipoproteins called myelin, which forms insulating sheaths at along parts of the axon.

The myelin sheath plays an important role in conducting electrical impulses or action potentials.

Action potentials propagate along the axon when sodium ions move into the cell through ion channels.

In sections with a myelin sheath, there are no ion channels, but sections in between, called nodes of Ranvier, have a ton of ion channels.

The action potential therefore doesn’t have to move along each section of the neuron, but rather from node to node, resulting in super fast saltatory conduction.

Also, the Schwann cells express a gene called neurofibromin 2, or NF2, which encodes a protein called merlin.

In schwann cells, merlin acts as a tumor suppressor, meaning it prevents the Schwann cells from dividing uncontrollably.

And that’s exactly what happens with a schwannoma, the schwann cells start dividing uncontrollably.

No one knows what causes most schwannomas from developing. The majority of schwannomas are solitary tumors of Schwann cells which are found around peripheral nerves.

They are usually benign meaning that the cells don’t invade surrounding tissue structures, and schwannomas therefore don’t metastasize to distant locations.

Most often, they arise around cranial nerve 8, the vestibulocochlear nerve, and are known as vestibular schwannomas, or acoustic neuromas, though acoustic neuroma is not that precise a description.


Acoustic neuroma is a benign tumor that arises from the Schwann cells that surround the eighth cranial (vestibulocochlear) nerve. The symptoms of acoustic neuroma vary depending on the size and location of the tumor, but they can include hearing loss, tinnitus (ringing in the ears), dizziness, and facial weakness. The cause of acoustic neuroma is not fully understood, but it appears to be due to a combination of environmental and genetic factors.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "The tumour-suppressor genes NF2/Merlin and Expanded act through Hippo signalling to regulate cell proliferation and apoptosis" Nature Cell Biology (2005)
  6. "Clinical Features and Treatment of Penile Schwannoma: A Systematic Review" Clinical Genitourinary Cancer (2016)
  7. "Extracranial head and neck schwannomas—A 10-year review" Auris Nasus Larynx (2007)
  8. "News on the genetics, epidemiology, medical care and translational research of Schwannomas" Journal of Neurology (2006)

Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.