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{{Acoustic neuroma}}
{{Acoustic neuroma}}
{{CMG}}
==Overview==
Acoustic neuromas may occur sporadically, or in some cases occur as part of [[Neurofibromatosis type I|von Recklinhausen neurofibromatosis]], in which case the neuroma may take on one of two forms.
*In '''Neurofibromatosis type I''', a schwannoma may sporadically involve the 8th nerve, usually in adult life, but may involve any other cranial nerve or the spinal root. Bilateral acoustic neuromas are rare in this type.
*In '''Neurofibromatosis type II''', bilateral acoustic neuromas are the hallmark and typically present before the age of 21. These tumors tend to involve the entire extend of the nerve and show a strong [[autosomal dominant]] inheritance. Incidence is about 5 to 10%.


The usual tumor in the adult presents as a solitary tumor, originating in the nerve. It usually arises from the vestibular portion of the 8th nerve, just within the internal auditory canal. As the tumor grows, it usually extends into the posterior fossa to occupy the angle between the cerebellum and the pons ([[cerebellopontine angle]]). Because of its position, it may also compress the 5th, 7th, and less often, the 9th and 10th cranial nerves. Later, it may compress the pons and lateral medulla, causing obstruction of the [[cerebrospinal fluid]] and increased [[intracranial pressure]].  
{{CMG}}{{AE}}{{Simrat}} {{M.B}} {{Sab}}
==Overview==
 
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==
* 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 (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 ==
* 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]].
* [[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]]
 
==== 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
 
==Microscopic Pathology==
===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>
 
'''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==
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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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