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{{Acoustic neuroma}}
{{Acoustic neuroma}}


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==Overview==
==Overview==


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==Pathophysiology==
==Pathophysiology==
* Acoustic neuromas are [[benign]] tumors ([[WHO]] grade 1), which usually arise from the intracanalicular segment of the vestibular portion of the [[vestibulocochlear]] [[nerve]] (CN VIII), near the transition point between glial and Schwann cells (Obersteiner-Redlich zone).   
* Acoustic neuromas are [[benign]] [[Tumor|tumors]] ([[WHO]] [[Grading (tumors)|grade]] 1), usually arising from the intracanalicular segment of the vestibular portion of the [[Vestibulocochlear nerve|vestibulocochlear nerve (CN VIII)]], near the transition point between [[Glial cell|glial]] and [[Schwann cell|Schwann cells]] (Obersteiner-Redlich zone).   
* An acoustic neuroma arises from a type of cell known as the Schwann [[cell]].
* An acoustic neuroma arises from a type of [[Cell (biology)|cell]] known as the [[Schwann cell]]. These [[Cell (biology)|cells]] form an insulating layer over all [[Nerve|nerves]] of the [[peripheral nervous system]] (i.e., [[Nerve|nerves]] outside of the [[central nervous system]]) including the [[Vestibulocochlear nerve|eighth cranial nerve]]. 
** These cells form an insulating layer over all nerves of the [[peripheral nervous system]] (i.e., nerves outside of the [[central nervous system]]) including the eighth [[cranial]] nerve. 
* Most acoustic neuromas are found along the [[Vestibular nerve|vestibular]] portion of the [[Vestibulocochlear nerve|eighth cranial nerve]].   
* The eighth [[cranial nerve]] is separated into two branches:
* As these [[Tumor|tumors]] are made up of [[Schwann cells]], and usually located along the [[Vestibular nerve|vestibular]] portion of the [[Vestibulocochlear nerve|eighth cranial nerve]], many [[Physician|physicians]] prefer to use the term, "[[Acoustic neuroma|vestibular schwannoma]]". However, the term acoustic neuroma is still used more often in the [[medical literature]].<ref name="radio">Acoustic Schwannoma. Radiopedia(2015) http://radiopaedia.org/articles/acoustic-schwannoma Accessed on October 2 2015</ref>   
** The cochlear branch, which transmits sound to the brain
* Acoustic neuromas are well circumscribed encapsulated [[Mass|masses]], which unlike neuromas, arise from but are separate from [[nerve]] fibers.
** The vestibular branch, which transmits balance information to the [[brain]]  
* Most acoustic neuromas occur on the vestibular portion of the eighth cranial nerve.   
* As these tumors are made up of [[Schwann cells]], and usually occur on the vestibular portion of the eighth cranial nerve, many physicians prefer the use of the term vestibular schwannoma. However, the term acoustic neuroma is still used more often in the medical literature.<ref name="radio">Acoustic Schwannoma. Radiopedia(2015) http://radiopaedia.org/articles/acoustic-schwannoma Accessed on October 2 2015</ref>   
* Acoustic neuromas are well circumscribed encapsulated masses, which unlike neuromas, arise from but are separate from nerve fibers, which they usually splay and displace rather than incorporated.dsfsdfsdf


== Genetic ==
== Genetic ==
* One the most knowable causes of [[acoustic neuroma]] is [[Neurofibromatosis type II|Neurofibromatosis type 2]] (NF2).
* One the most common causes of acoustic neuroma is [[Neurofibromatosis type II|neurofibromatosis type 2 (NF2)]], an [[Dominance relationship|autosomal dominant]] disease caused by loss of function [[Mutation|mutation]].  
* [[Neurofibromatosis type II|Neurofibromatosis Type 2]] is an [[Dominance relationship|autosomal dominant]] disease caused by loss of function [[Mutation|mutations]]. 
* [[Genetics|Genetic]] studies have linked both sporadic and [[Neurofibromatosis type II|NF2]]-associated acoustic neuromas to a single [[gene]], the NF2 [[gene]], located on [[chromosome 22]] band q11–13.1.  
* Approximately 50% of reported NF2 cases represent new mutations for which no other affected family member can be identified.
* NF2 [[gene]] is on [[chromosome]] 22q12.2 that encodes a 595–[[amino acid]] [[protein]] named “moesin- ezrin-radixin–like protein,” otherwise known as “merlin” or “schwannomin.”<ref>{{Cite journal
| author = [[Michael E. Sughrue]], [[Andrea H. Yeung]], [[Martin J. Rutkowski]], [[Steven W. Cheung]] & [[Andrew T. Parsa]]
| title = Molecular biology of familial and sporadic vestibular schwannomas: implications for novel therapeutics
| journal = [[Journal of neurosurgery]]
| volume = 114
| issue = 2
| pages = 359–366
| year = 2011
| month = February
| doi = 10.3171/2009.10.JNS091135
| pmid = 19943731
}}</ref>
* Merlin protein linked with other proteins in [[Cell (biology)|cell]] and are involved in linking [[Cytoskeleton|cytoskeletal]] components with the [[Cell membrane|plasma membrane]] and are located in actin-rich surface projections such as [[Microvillus|microvilli]], membrane surfaces, and cell contact regions.
* [[Dephosphorylation|Dephosphorylated]] Merlin proteins are active and roll in the normal [[cell growth]], [[Phosphorylation|phosphorylated]] Merlin ( [[Chemical synthesis|synthesized]] due to a [[mutation]] in NF2 [[gene]] that causes to produce a truncated Merlin protein) inactivated and can not play normal roll in [[cell growth]] and causes increased [[cell growth]].<ref name=":0">{{Cite journal|last=Wippold II|first=F.J|date=2007|title=Neuropathology for the Neuroradiologist: Antoni A and Antoni B Tissue Patterns|url=|journal=AJNR Am J Neuroradiol|volume=|pages=|via=}}</ref><ref>{{Cite journal|last=SUGHRUE|first=MICHAEL E.|date=2011|title=Molecular biology of familial and sporadic vestibular schwannomas: implications for novel therapeutics|url=|journal=J Neurosurg|volume=114|pages=|via=}}</ref>


== Associated Conditions ==
== Associated Conditions ==
*Childhood exposure to [[radiation]] of the [[head]] and [[neck]] may be associated with acoustic neuroma.<ref>{{Cite journal
*Acoustic neuroma is strongly associated with [[Neurofibromatosis type II|neurofibromatosis type 2 (NF2)]].<ref>{{Cite journal
  | author = [[Arthur B. Schneider]], [[Elaine Ron]], [[Jay Lubin]], [[Marilyn Stovall]], [[Eileen Shore-Freedman]], [[Jocelyn Tolentino]] & [[Barbara J. Collins]]
  | author = [[M. M. Eibl]], [[R. Ahmad]], [[H. M. Wolf]], [[Y. Linnau]], [[E. Gotz]] & [[J. W. Mannhalter]]
| title = Acoustic neuromas following childhood radiation treatment for benign conditions of the head and neck
  | title = A component of factor VIII preparations which can be separated from factor VIII activity down modulates human monocyte functions
| journal = [[Neuro-oncology]]
  | journal = [[Blood]]
| volume = 10
  | volume = 69
| issue = 1
  | issue = 4
| pages = 73–78
  | pages = 1153–1160
| year = 2008
  | year = 1987
| month = February
  | month = April
| doi = 10.1215/15228517-2007-047
  | pmid = 3030465
| pmid = 18079359
}}</ref><ref>{{Cite journal
| author = [[E. Shore-Freedman]], [[C. Abrahams]], [[W. Recant]] & [[A. B. Schneider]]
  | title = Neurilemomas and salivary gland tumors of the head and neck following childhood irradiation
  | journal = [[Cancer]]
  | volume = 51
  | issue = 12
  | pages = 2159–2163
  | year = 1983
  | month = June
  | pmid = 6850504
}}</ref>
}}</ref>
*Exposure to high-dose ionizing radiation is the only definite environmental risk factor associated with an increased risk of developing an acoustic neuroma.<ref>{{Cite journal
 
| author = [[Oyebode Taiwo]], [[Deron Galusha]], [[Baylah Tessier-Sherman]], [[Sharon Kirsche]], [[Linda Cantley]], [[Martin D. Slade]], [[Mark R. Cullen]] & [[A. Michael Donoghue]]
== Gross Pathology ==
| title = Acoustic neuroma: potential risk factors and audiometric surveillance in the aluminium industry
On [[gross pathology]], following are the characteristic findings of acoustic neuroma:
| journal = [[Occupational and environmental medicine]]
* Rubbery-firm with a pale, gray color<ref>{{Cite journal
| volume = 71
  | author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| issue = 9
  | title = Acoustic Neuroma (Vestibular Schwannoma)
| pages = 624–628
  | year = 2019
| year = 2014
  | month = January
| month = September
  | pmid = 29262098
| doi = 10.1136/oemed-2014-102094
| pmid = 25015928
}}</ref><ref>{{Cite journal
  | author = [[Mantao Chen]], [[Zuoxu Fan]], [[Xiujue Zheng]], [[Fei Cao]] & [[Liang Wang]]
  | title = Risk Factors of Acoustic Neuroma: Systematic Review and Meta-Analysis
| journal = [[Yonsei medical journal]]
| volume = 57
| issue = 3
| pages = 776–783
  | year = 2016
  | month = May
| doi = 10.3349/ymj.2016.57.3.776
  | pmid = 26996581
}}</ref>
}}</ref>
*A concomitant history of having had a [[parathyroid]] [[adenoma]] may have an increased risk of developing vestibular schwannoma.<ref>{{Cite journal
* Well-defined capsule
  | author = [[L. Magnus Backlund]], [[Dan Grander]], [[Lena Brandt]], [[Per Hall]] & [[Anders Ekbom]]
* Different degrees of [[vascularity]]
  | title = Parathyroid adenoma and primary CNS tumors
 
| journal = [[International journal of cancer]]
==== On Cut Section ====
| volume = 113
* Pale gray and firm<ref>{{Cite journal
| issue = 6
  | author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| pages = 866–869
  | title = Acoustic Neuroma (Vestibular Schwannoma)
  | year = 2005
  | year = 2019
  | month = March
  | month = January
| doi = 10.1002/ijc.20743
  | pmid = 29262098
  | pmid = 15515018
}}</ref>
}}</ref>
* Fine trabeculated appearance
* [[Cyst|Cystic]] degeneration
* [[Bleeding|Hemorrhage]]
* [[Calcification]]
* Xanthomatous changes


==Microscopic Pathology==
==Microscopic Pathology==
* In 1920, Nils Ragnar Euge`ne Antoni (1887–1968), a Swedish neurologist and researcher described 2 distinct patterns of cellular architecture in the peripheral [[Nerve sheath tumor|nerve sheath tumors]], based his observations on analysis of 30 cases and described a “fibrillary, intensely polar, elongated appearing tissue type” which he called “tissue type A.” <ref name=":0" />
===On Light Microscopy===
* These highly cellular regions were eventually referred to as Antoni A regions by later authors. <ref name=":0" />
*The [[tumor]] is made up of [[Spindle neuron|spindle cells]] with elongated [[Cell nucleus|nuclei]] and fibrillary [[cytoplasm]].<ref>{{Cite journal
* Antoni also described seemingly distinct loose microcystic tissue adjacent to the Antoni A regions, and these came to be known as Antoni B regions.<ref name=":0" />
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
'''They can display two types of growth patterns:<ref name=":0" />'''
| title = Acoustic Neuroma (Vestibular Schwannoma)
*Antoni A
| year = 2019
**Elongated [[cells]] with [[cytoplasmic]] processes arranged in [[fascicles]]  
| month = January
**Little [[stromal]] [[matrix]]
| pmid = 29262098
**Verocay bodies: nuclear free zones of processes lying between regions of nuclear palisading
}}</ref>
*Antoni B
*The [[Spindle neuron|spindle cells]] are arranged in two ways:
**Loose meshwork of cells
'''1. Antoni A'''
**Less densely [[cellular]]
*Antoni A [[Tissue (biology)|tissue]] is small with organized and interwoven course of elongated [[Bipolar cell|bipolar cells]].<ref>{{Cite journal
**Microcysts and myxoid change
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
*Photomicrograph of Antoni A tissue and Antoni B tissue within a schwannoma. The highly cellular Antoni A region on the right of the field is contrasted with the loosely organized hypocellular Antoni B region on left of the field (hematoxylin-eosin, original magnification 400).
| title = Acoustic Neuroma (Vestibular Schwannoma)
[[File:Screen Shot 1397-03-01 at 19.14.06.jpg|alt=Photomicrograph of Antoni A tissue and Antoni B tissue within a schwannoma. The highly cellular Antoni A region on the right of the field is contrasted with the loosely organized hypocellular Antoni B region on left of the field (hematoxylin-eosin, original magnification 400).|none|thumb|Photomicrograph of Antoni A tissue and Antoni B tissue within a schwannoma. The highly cellular Antoni A region on the right of the field is contrasted with the loosely organized hypocellular Antoni B region on left of the field (hematoxylin-eosin, original magnification  400). ]]
| year = 2019
| month = January
| pmid = 29262098
}}</ref>
*The spiral framework, formed by the arrangement of the [[Cell nucleus|nuclei]] and fibers, can resemble a [[meningioma]].
*Verocay bodies can also be seen.<ref name="WippoldLubner2007">{{cite journal|last1=Wippold|first1=F.J.|last2=Lubner|first2=M.|last3=Perrin|first3=R.J.|last4=Lammle|first4=M.|last5=Perry|first5=A.|title=Neuropathology for the Neuroradiologist: Antoni A and Antoni B Tissue Patterns|journal=American Journal of Neuroradiology|volume=28|issue=9|year=2007|pages=1633–1638|issn=0195-6108|doi=10.3174/ajnr.A0682}}</ref>
 
'''2. Antoni B'''
*It is represented by a random grouping of [[Cell (biology)|cells]] around foci of [[necrosis]], [[Cyst|cystic]] change, [[Bleeding|hemorrhage]], and [[Blood vessel|blood vessels]].<ref>{{Cite journal
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| title = Acoustic Neuroma (Vestibular Schwannoma)
| year = 2019
| month = January
| pmid = 29262098
}}</ref>
*This [[Tissue (biology)|tissue]] can also have a variable amount of [[Lymphocyte|lymphocytic]] infiltration.
===On Electron Microscopy===
The following findings on [[Electron microscope|electron microscopy]] are characteristic of an acoustic neuroma:
*Characteristic [[basement membrane]] of the [[Schwann cell|schwann cells]].<ref>{{Cite journal
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
  | title = Acoustic Neuroma (Vestibular Schwannoma)
| year = 2019
| month = January
| pmid = 29262098
}}</ref><ref>{{Cite journal
| author = [[Lukas D. Landegger]], [[Jessica E. Sagers]], [[Sonam Dilwali]], [[Takeshi Fujita]], [[Mehmet I. Sahin]] & [[Konstantina M. Stankovic]]
| title = A Unified Methodological Framework for Vestibular Schwannoma Research
| journal = [[Journal of visualized experiments : JoVE]]
| issue = 124
  | year = 2017
| month = June
| doi = 10.3791/55827
| pmid = 28654042
}}</ref>
*Wide-spaced [[collagen]].


==References==
==References==

Latest revision as of 16:18, 23 April 2019

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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] Mohsen Basiri M.D. Sabawoon Mirwais, M.B.B.S, M.D.[3]

Overview

Acoustic neuroma arises from Schwann cells, which are the cells involved in the conduction of nervous impulses along axons, nerve development and regeneration. On microscopic histopathological analysis, acoustic neuroma may display two types of growth patterns: Antoni type A and Antoni type B. Antoni type A growth pattern is composed of elongated cells with cytoplasmic processes arranged in fascicles, little stromal matrix and verocay bodies. Antoni type B growth pattern is composed of loose meshwork of cells, less dense cellular matrix, microcysts and myxoid change.

Pathophysiology

Genetic

Associated Conditions

Gross Pathology

On gross pathology, following are the characteristic findings of acoustic neuroma:

  • Rubbery-firm with a pale, gray color[3]
  • Well-defined capsule
  • Different degrees of vascularity

On Cut Section

Microscopic Pathology

On Light Microscopy

1. Antoni A

  • Antoni A tissue is small with organized and interwoven course of elongated bipolar cells.[6]
  • The spiral framework, formed by the arrangement of the nuclei and fibers, can resemble a meningioma.
  • Verocay bodies can also be seen.[7]

2. Antoni B

On Electron Microscopy

The following findings on electron microscopy are characteristic of an acoustic neuroma:

References

  1. ↑ Acoustic Schwannoma. Radiopedia(2015) http://radiopaedia.org/articles/acoustic-schwannoma Accessed on October 2 2015
  2. ↑ M. M. Eibl, R. Ahmad, H. M. Wolf, Y. Linnau, E. Gotz & J. W. Mannhalter (1987). "A component of factor VIII preparations which can be separated from factor VIII activity down modulates human monocyte functions". Blood. 69 (4): 1153–1160. PMID 3030465. Unknown parameter |month= ignored (help)
  3. ↑ Joshua Greene & Mohammed A.. Al-Dhahir (2019). "Acoustic Neuroma (Vestibular Schwannoma)". PMID 29262098. Unknown parameter |month= ignored (help)
  4. ↑ Joshua Greene & Mohammed A.. Al-Dhahir (2019). "Acoustic Neuroma (Vestibular Schwannoma)". PMID 29262098. Unknown parameter |month= ignored (help)
  5. ↑ Joshua Greene & Mohammed A.. Al-Dhahir (2019). "Acoustic Neuroma (Vestibular Schwannoma)". PMID 29262098. Unknown parameter |month= ignored (help)
  6. ↑ Joshua Greene & Mohammed A.. Al-Dhahir (2019). "Acoustic Neuroma (Vestibular Schwannoma)". PMID 29262098. Unknown parameter |month= ignored (help)
  7. ↑ Wippold, F.J.; Lubner, M.; Perrin, R.J.; Lammle, M.; Perry, A. (2007). "Neuropathology for the Neuroradiologist: Antoni A and Antoni B Tissue Patterns". American Journal of Neuroradiology. 28 (9): 1633–1638. doi:10.3174/ajnr.A0682. ISSN 0195-6108.
  8. ↑ Joshua Greene & Mohammed A.. Al-Dhahir (2019). "Acoustic Neuroma (Vestibular Schwannoma)". PMID 29262098. Unknown parameter |month= ignored (help)
  9. ↑ Joshua Greene & Mohammed A.. Al-Dhahir (2019). "Acoustic Neuroma (Vestibular Schwannoma)". PMID 29262098. Unknown parameter |month= ignored (help)
  10. ↑ Lukas D. Landegger, Jessica E. Sagers, Sonam Dilwali, Takeshi Fujita, Mehmet I. Sahin & Konstantina M. Stankovic (2017). "A Unified Methodological Framework for Vestibular Schwannoma Research". Journal of visualized experiments : JoVE (124). doi:10.3791/55827. PMID 28654042. Unknown parameter |month= ignored (help)


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