Sensorineural Hearing Loss: Acoustic Neuroma

Acoustic neuromas (AN) are benign tumors that originate from the root of the eighth cranial nerve. Although they are benign, their position in the cerebellopontine angle can produce severe morb­idity due to cranial nerve and brainstem com­pression.

• Presentation. Acoustic neuroma most commonly occurs in middle age, with 50% of patients between the ages of 50 and…

• Nomenclature. The nomenclature is confusing. In addition to the term “neuroma,” these common neoplasms of cranial and spinal roots are sometimes known as…

• Sporadic vs. Hereditary. Acoustic neuroma occurs in both sporadic and hereditary forms. Unilateral sporadic tumors account for…

• Tumor Growth Rate. The rate of tumor growth is variable with most patients, demonstrating very…

Audiometric Tests

On the basis of audiometric tests, hearing loss can be distinguished as conductive or senso­rineural. Conductive hearing loss occurs when there is disruption of sound transmission from the external auditory canal/tympanic membrane to the oval window. Sensorineural hearing loss…

Signs and Symptoms

• Hearing Loss. The classic clinical syndrome produced by acoustic neuromas includes…

• Disequilibrium. Although vestibular symptoms and signs are usually mild and present…2

• Headache. Tumor size can be estimated from clinical symptoms and signs. As tumors enlarge, they progressively efface the cerebellopontine angle cistern and compress the…

• Trigeminal Nerve Involvement. Involvement of the trigeminal nerve results in slowed corneal…

Screening

The possibility of an acoustic neuroma should be considered in all patients with unilateral sensorineural hearing loss and/or vestibular…

For a select group of patients, nonoperative management may be desirable…

Radiological Evaluation

Small acoustic neuromas produce thickening of the neurovascular bundle, usually within the internal auditory canal. Typically, this is apparent upon comparison with the contralateral side. MRI can detect even minimal nerve enlarge­ment. Larger tumors are readily apparent, often filling the internal auditory canal and extending into the cerebellopontine angle cistern, where they may be observed compressing the adjacent brain stem and/or cranial nerves.

 

Acoustic Neuroma

 

♦ Contrast-Enhanced MRI

On contrast-enhanced MRI studies, it is possible to detect acoustic neuromas in apparently normal-sized nerves.3 Acoustic neuromas display marked and consistent early enhancement after administration of contrast.

The large number of patients who require imaging to exclude acoustic neuroma argues for the use of…

Discussion

MRI has greatly improved the diagnosis and treatment of patients with acoustic neuromas. In addition, it has proved effective in detecting other sensorineural hearing loss-causing conditions that pre­viously were suspected clinically but confirmed only by…

♦ MRI vs. CT

Various clinical, audiometric, and imaging tests are available to help resolve clinical suspicions. Imaging studies are indicated when clinical history, physical examination, or audiometric…

Conclusion

This article was edited from Sensorineural Hearing Loss: Acoustic Neuroma by the same author. The complete unabridged version, including all of its images and references, is available at the Apple iBooks Store. See our other Neuroradiology articles here.

 

REFERENCES

  1. Koors PD, Thacker LR, Coelho DH. ABR in the diagnosis of vestibular schwannomas: a meta-analysis. Am J Otolaryngol. 2013 May-Jun;34(3):195-204.
  2. Smouha E. Inner ear disorders. NeuroRehabilitation. 2013;32(3):455-62.
  3. Hilly O, Chen JM, Birch J, et al. Diffusion Tensor Imaging Tractography of the Facial Nerve in Patients With Cerebellopontine Angle Tumors. Otol Neurotol. 2016 Apr;37(4):388-93.
Alan Jackson, Ph.D., MB Ch.B (Hons), MRCP, FRCR
Alan Jackson, Ph.D., MB Ch.B (Hons), MRCP, FRCR
Professor of Neuroradiology, University of Manchester, UK | Faculty Page