Acoustic neuroma pathophysiology: Difference between revisions

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{{Acoustic neuroma}}
{{Acoustic neuroma}}
{{CMG}}{{AE}}{{Simrat}}
 
{{CMG}}{{AE}}{{Simrat}} {{M.B}} {{Sab}}
==Overview==
==Overview==


Acoustic neuroma arises from [[Schwann cells]], which are the cells that are normally 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.<ref name="radio">Acoustic Schwannoma. Radiopedia(2015) http://radiopaedia.org/articles/acoustic-schwannoma Accessed on October 2 2015</ref> Antoni type A growth pattern is composed of elongated cells with cytoplasmic process arranged in fascicles, little stromal [[matrix]] and verocay bodies. Antoni type B growth pattern is composed of loose meshwork of cells, less densely cellular matrix, microcysts and myxoid change.
Acoustic neuroma arises from [[Schwann cells]], which are the [[Cell (biology)|cells]] involved in the conduction of [[Nervous system|nervous]] impulses along [[axons]], [[nerve]] development and [[Nerve regeneration|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 [[Cell (biology)|cells]] with [[Cytoplasm|cytoplasmic]] processes arranged in [[Fascicle|fascicles]], little [[stromal]] [[matrix]] and verocay bodies. Antoni type B growth pattern is composed of loose meshwork of [[Cell (biology)|cells]], less dense [[Cell (biology)|cellular]] [[matrix]], microcysts and myxoid change.


==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). An acoustic neuroma arises from a type of cell known as the Schwann [[cell]]. 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. The eighth [[cranial nerve]] is separated into two branches the cochlear branch, which transmits sound to the brain and the vestibular branch, which transmits balance information to the [[brain]]. Most acoustic neuromas occur on the vestibular portion of the eighth cranial nerve. Because 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 [[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).
They 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.  
* 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]].  
* Most acoustic neuromas are found along the [[Vestibular nerve|vestibular]] portion of the [[Vestibulocochlear nerve|eighth cranial nerve]].
* 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>
* Acoustic neuromas are well circumscribed encapsulated [[Mass|masses]], which unlike neuromas, arise from but are separate from [[nerve]] fibers.


== Genetic ==
== Genetic ==
One the most knowable causes of acoustic neuroma is Neurofibromatosis type 2 (NF2). Neuro bromatosis Type 2 is an autosomal dominant disease caused by loss of function mutations. 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.” Merlin protein linked with other proteins in cell and are involved in linking cytoskeletal components with the plasma membrane and are located in actin-rich surface projections such as microvilli, membrane surfaces, and cell contact regions. Dephosphorylated Merlin proteins are active and roll in the normal cell growth, phosphorylated Merlin ( 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>
* 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]].  
[[File:Merlin protein roll in cell growth.jpg|alt=|none|thumb|431x431px|(Right) Dephosphorylated Merlin protein is active and roll in the normal cell growth (Left) phosphorylated Merlin ( 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.]]
* [[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.  
 
== Associated Conditions ==
*Acoustic neuroma is strongly associated with [[Neurofibromatosis type II|neurofibromatosis type 2 (NF2)]].<ref>{{Cite journal
| author = [[M. M. Eibl]], [[R. Ahmad]], [[H. M. Wolf]], [[Y. Linnau]], [[E. Gotz]] & [[J. W. Mannhalter]]
| title = A component of factor VIII preparations which can be separated from factor VIII activity down modulates human monocyte functions
| journal = [[Blood]]
| volume = 69
| issue = 4
| pages = 1153–1160
| year = 1987
| month = April
| pmid = 3030465
}}</ref>
 
== Gross Pathology ==
On [[gross pathology]], following are the characteristic findings of acoustic neuroma:
* Rubbery-firm with a pale, gray color<ref>{{Cite journal
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| title = Acoustic Neuroma (Vestibular Schwannoma)
| year = 2019
| month = January
| pmid = 29262098
}}</ref>
* Well-defined capsule
* Different degrees of [[vascularity]]


===Microscopic Pathology===
==== On Cut Section ====
* Pale gray and firm<ref>{{Cite journal
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| title = Acoustic Neuroma (Vestibular Schwannoma)
| year = 2019
| month = January
| pmid = 29262098
}}</ref>
* Fine trabeculated appearance
* [[Cyst|Cystic]] degeneration
* [[Bleeding|Hemorrhage]]
* [[Calcification]]
* Xanthomatous changes


==== What Are Antoni A and Antoni B Patterns? ====
==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 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.” These highly cellular regions were eventually referred to as Antoni A regions by later authors. Antoni also described seemingly dis- tinct loose microcystic tissue adjacent to the Antoni A regions, and these came to be known as Antoni B regions.<ref name=":0" />
===On Light Microscopy===
*The [[tumor]] is made up of [[Spindle neuron|spindle cells]] with elongated [[Cell nucleus|nuclei]] and fibrillary [[cytoplasm]].<ref>{{Cite journal
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| title = Acoustic Neuroma (Vestibular Schwannoma)
| year = 2019
| month = January
| pmid = 29262098
}}</ref>
*The [[Spindle neuron|spindle cells]] are arranged in two ways:
'''1. Antoni A'''
*Antoni A [[Tissue (biology)|tissue]] is small with organized and interwoven course of elongated [[Bipolar cell|bipolar cells]].<ref>{{Cite journal
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
| title = Acoustic Neuroma (Vestibular Schwannoma)
| 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>


They can display two types of growth patterns:
'''2. Antoni B'''
*Antoni A
*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
**Elongated [[cells]] with [[cytoplasmic]] processes arranged in [[fascicles]]  
| author = [[Joshua Greene]] & [[Mohammed A.. Al-Dhahir]]
**Little [[stromal]] [[matrix]]
| title = Acoustic Neuroma (Vestibular Schwannoma)
**Verocay bodies: nuclear free zones of processes lying between regions of nuclear palisading
| year = 2019
*Antoni B
| month = January
**Loose meshwork of cells
| pmid = 29262098
**Less densely [[cellular]]
}}</ref>
**Microcysts and myxoid change
*This [[Tissue (biology)|tissue]] can also have a variable amount of [[Lymphocyte|lymphocytic]] infiltration.
[[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). ]]
===On Electron Microscopy===
<ref name=":0" />
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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