Acoustic neuroma other diagnostic studies
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Other diagnostic studies
Hearing test (audiometry)
- Audiometry as the best initial screening laboratory test for the diagnosis of acoutic neuroma, can detect asymmetric sensorineural hearing impairment in about ninety five percent of patients.
- Pure tone (audiogram) and speech audiometry should be performed, however test results does not essentially correlate with tumor size.
- Speech audiometry typically consists of two parts: the speech reception threshold (SRT) and the word discrimination score.
- The speech discrimination score is usually markedly reduced in the affected ear and out of proportion to the measured hearing loss.
Auditory brainstem response test
- Brainstem-evoked response audiometry (ABR, BAER, or BSER) may be done in some cases can be used in patients with unexplained asymmetries in standard audiometric testing as a further screening measure
- This test provides information on the passage of an electrical impulse along the circuit from the inner ear to the brainstem pathways.
- An acoustic neuroma can interfere with the passage of this electrical impulse through the cochlear nerve at the site of tumor growth in the internal auditory canal, even when the hearing is not necessarily impaired.
- This implies the possible diagnosis of an acoustic neuroma when the test result is abnormal. 20-35% of acoustic neuroma tumors smaller than 1 cm are missed by ABR screening techniques. the false negative rate can be as high as 30 percent with small vestibular schwannomas, and there is a 10 percent false positive rate
- An abnormal auditory brainstem response test should be followed by an MRI.
- If an MRI is not available or cannot be performed, a computerized tomography scan (CT scan) with contrast is suggested for patients in whom an acoustic neuroma is suspected.
- The combination of CT scan and audiogram approach the reliability of MRI in making the diagnosis of acoustic neuroma.
References
- Evans, D. Gareth R.; Moran, Anthony; King, Andrew; Saeed, S.; Gurusinghe, Nihal; Ramsden, Richard (2005). "Incidence of Vestibular Schwannoma and Neurofibromatosis 2 in the North West of England over a 10-year Period: Higher Incidence than Previously Thought". Otology & Neurotology. 26 (1): 93–7. doi:10.1097/00129492-200501000-00016. PMID 15699726.
- Shin, Masahiro; Ueki, Keisuke; Kurita, Hiroki; Kirino, Takaaki (2002). "Malignant transformation of a vestibular schwannoma after gamma knife radiosurgery". The Lancet. 360 (9329): 309–10. doi:10.1016/S0140-6736(02)09521-1. PMID 12147377.
- Samii, Madjid; Gerganov, Venelin; Samii, Amir (2006). "Improved preservation of hearing and facial nerve function in vestibular schwannoma surgery via the retrosigmoid approach in a series of 200 patients". Journal of Neurosurgery. 105 (4): 527–35. doi:10.3171/jns.2006.105.4.527. PMID 17044553.
- Pollock, Bruce E.; Driscoll, Colin L.W.; Foote, Robert L.; Link, Michael J.; Gorman, Deborah A.; Bauch, Christopher D.; Mandrekar, Jayawant N.; Krecke, Karl N.; Johnson, Craig H. (2006). "Patient Outcomes after Vestibular Schwannoma Management: A Prospective Comparison of Microsurgical Resection and Stereotactic Radiosurgery". Neurosurgery. 59 (1): 77–85, discussion 77–85. doi:10.1227/01.NEU.0000219217.14930.14. PMID 16823303.
- Prasad, Dheerendra; Steiner, Melita; Steiner, Ladislau (2000). "Gamma surgery for vestibular schwannoma". Journal of Neurosurgery. 92 (5): 745–59. doi:10.3171/jns.2000.92.5.0745. PMID 10794287.
- Stangerup, Sven-Eric; Caye-Thomasen, Per; Tos, Mirko; Thomsen, Jens (2006). "The natural history of vestibular schwannoma". Otology & Neurotology. 27 (4): 547–52. doi:10.1097/01.mao.0000217356.73463.e7. PMID 16791048.
- Kanzaki, Jin; Tos, Mirko; Sanna, Mario; Moffat, David A. (2003). "New and modified reporting systems from the consensus meeting on systems for reporting results in vestibular schwannoma". Otology & Neurotology. 24 (4): 642–8, discussion 648–9. doi:10.1097/00129492-200307000-00019. PMID 12851559.
- Tos, Mirko; Stangerup, Sven-Eric; Cayé-Thomasen, Per; Tos, Tina; Thomsen, Jens (2004). "What Is the Real Incidence of Vestibular Schwannoma?". Archives of Otolaryngology–Head & Neck Surgery. 130 (2): 216–20. doi:10.1001/archotol.130.2.216. PMID 14967754.