Schwannoma
Updates to Article Attributes
Schwannomas are benign tumours of schwann cell origin and are the most common tumour of peripheral nerves.
Locations include:
- cranial nerves
. Any: any cranial nerve may be involved, except CNI andCN2 whichCNII, which lack sheaths composed of schwann cells. The most commonly involved cranial nerves include:- CN VIII (acoustic neuroma), most commonly the superior portion of vestibular nerve (most common)
- CN V (2nd most common)
- CN VII (3rd most common)
- Jugular foramen (CN IX, X, XI)
- CN XII
( hypoglossal(hypoglossal schwannomas are very rare)
- spinal nerve roots
- intercostal nerves: intercostal nerve schwannoma
- flexor surfaces of upper and lower limbs (specifically ulnar and peroneal nerves)
- posterior mediastinum
- retroperitoneum
- Intracerebral (very rare)
This article provides a general overview of schwannomas. For a discussion of schwannomas located at specific sites, please refer to the relevant articles.
Epidemiology
Peak presentation is in the 5th-6th5th-6th decades. When they occur in patients with neurofibromatosis type 2 (NF2), schwannomas usually present by the 3rd3rd decade 4. There is no sex predilection.
Associations
Most schwannomas are solitary (90%) 2 and sporadic, however there is an association with NF2 (abnormality of chromosome 22). Multiple schwannomas are characteristic of NF2. Approximately 18% of solitary schwannomas occur in patients with NF2 4.
There is also schwannomatosis, which consists ofmultiple schwannomas without concomitant involvement of cranial nerve VIII.
Clinical presentation
Presentation depends on location of the tumour.
Pathology
Schwannomas are benign encapsulated neoplasms of schwann cells (WHO grade I). They arise eccentrically from their parent nerve. They are composed of two cell types: Antoni A and Antoni B. The Antoni A cells are densely packed and arranged in fascicles; acellular areas lie between opposing rows of parallel nuclei (Verocay bodies). The Antoni B cells are less compact and are prone to cystic degeneration.
Pathologic variants include:
- cellular schwannomas (predominantly Antoni A tissue without Verocay bodies)
- melanotic schwannomas (dense melanin pigment)
- plexiform schwannomas (do not undergo malignant change, unlike plexiform neurofibromas)
Radiographic features
General imaging features of schwannomas include:
CT
- isodense to hypodense
- dense contrast enhancement
- small tumours show homogeneous enhancement
- larger tumours may show heterogeneous enhancement
- adjacent bone
remodellingremodeling may be seen
MRI
- cystic and fatty degeneration are common 4
- haemorrhage occurs in 5% of cases 3
- calcification is rare
- peripheral arachnoid cysts may be associated
- peritumoural oedema may be seen
Typical signal characteristics:
-
T1
-: isointense or hypointense -
T2:
- hyperintensehyperintense -
T1 C+ (Gd)
-: intense enhancement
The larger a schwannoma is, the more likely it is to show heterogeneity because of cystic degeneration or haemorrhage 3.
Treatment and prognosis
Schwannomas are slow growing-growing lesions. Surgery is the treatment of choice. As schwannomas do not infiltrate the parent nerve, they can usually be separated from it. Recurrence is unusual, even after complete resection. They almost never undergo malignant change.
-<li>cranial nerves. Any cranial nerve may be involved, except CNI and CN2 which lack sheaths composed of schwann cells. The most commonly involved cranial nerves include:<ul>- +<li>cranial nerves: any cranial nerve may be involved, except CNI and CNII, which lack sheaths composed of schwann cells. The most commonly involved cranial nerves include:<ul>
-<a href="/articles/trigeminal-schwannoma">CN V </a>(2<sup>nd</sup> most common)</li>- +<a href="/articles/trigeminal-schwannoma">CN V</a> (2<sup>nd</sup> most common)</li>
-<li>CN XII ( hypoglossal schwannomas are very rare)</li>- +<li>CN XII (hypoglossal schwannomas are very rare)</li>
-<li>intercostal nerves - <a href="/articles/intercostal-nerve-neurilemoma">intercostal nerve schwannoma</a>- +<li>intercostal nerves: <a href="/articles/intercostal-nerve-neurilemmoma">intercostal nerve schwannoma</a>
-</ul><p>This article provides a general overview of schwannomas. For a discussion of schwannomas located at specific sites, please refer to the relevant articles.</p><h4>Epidemiology</h4><p>Peak presentation is in the 5th-6th decades. When they occur in patients with neurofibromatosis type 2 (NF2), schwannomas usually present by the 3rd decade <sup>4</sup>. There is no sex predilection.</p><h5>Associations</h5><p>Most schwannomas are solitary (90%) <sup>2</sup> and sporadic, however there is an association with <a href="/articles/neurofibromatosis-type-2-3">NF2</a> (abnormality of chromosome 22). Multiple schwannomas are characteristic of NF2. Approximately 18% of solitary schwannomas occur in patients with NF2 <sup>4</sup>. There is also <a href="/articles/schwannomatosis">schwannomatosis</a>, which consists of<strong> </strong>multiple schwannomas without concomitant involvement of cranial nerve VIII.</p><h4>Clinical presentation</h4><p>Presentation depends on location of the tumour.</p><h4>Pathology</h4><p>Schwannomas are benign encapsulated neoplasms of schwann cells (WHO grade I). They arise eccentrically from their parent nerve. They are composed of two cell types: Antoni A and Antoni B. The Antoni A cells are densely packed and arranged in fascicles; acellular areas lie between opposing rows of parallel nuclei (Verocay bodies). The Antoni B cells are less compact and are prone to cystic degeneration.</p><p>Pathologic variants include:</p><ul>- +</ul><p>This article provides a general overview of schwannomas. For a discussion of schwannomas located at specific sites, please refer to the relevant articles.</p><h4>Epidemiology</h4><p>Peak presentation is in the 5<sup>th</sup>-6<sup>th</sup> decades. When they occur in patients with <a title="Neurofibromatosis type 2" href="/articles/neurofibromatosis-type-2-3">neurofibromatosis type 2 (NF2)</a>, schwannomas usually present by the 3<sup>rd</sup> decade <sup>4</sup>. There is no sex predilection.</p><h5>Associations</h5><p>Most schwannomas are solitary (90%) <sup>2</sup> and sporadic, however there is an association with <a href="/articles/neurofibromatosis-type-2-3">NF2</a> (abnormality of chromosome 22). Multiple schwannomas are characteristic of NF2. Approximately 18% of solitary schwannomas occur in patients with NF2 <sup>4</sup>.</p><p>There is also <a href="/articles/schwannomatosis">schwannomatosis</a>, which consists of<strong> </strong>multiple schwannomas without concomitant involvement of cranial nerve VIII.</p><h4>Clinical presentation</h4><p>Presentation depends on location of the tumour.</p><h4>Pathology</h4><p>Schwannomas are benign encapsulated neoplasms of schwann cells (WHO grade I). They arise eccentrically from their parent nerve. They are composed of two cell types: Antoni A and Antoni B. The Antoni A cells are densely packed and arranged in fascicles; acellular areas lie between opposing rows of parallel nuclei (Verocay bodies). The Antoni B cells are less compact and are prone to cystic degeneration.</p><p>Pathologic variants include:</p><ul>
-<li>adjacent bone remodelling may be seen</li>- +<li>adjacent bone remodeling may be seen</li>
-<strong>T1</strong> - isointense or hypointense</li>- +<strong>T1</strong>: isointense or hypointense</li>
-<strong>T2 </strong>- hyperintense</li>- +<strong>T2:</strong> hyperintense</li>
-<strong>T1 C+ (Gd)</strong> - intense enhancement</li>-</ul><p>The larger a schwannoma is, the more likely it is to show heterogeneity because of cystic degeneration or haemorrhage <sup>3</sup>.</p><h4>Treatment and prognosis</h4><p>Schwannomas are slow growing lesions. Surgery is the treatment of choice. As schwannomas do not infiltrate the parent nerve, they can usually be separated from it. Recurrence is unusual, even after complete resection. They almost never undergo malignant change.</p>- +<strong>T1 C+ (Gd)</strong>: intense enhancement</li>
- +</ul><p>The larger a schwannoma is, the more likely it is to show heterogeneity because of cystic degeneration or haemorrhage <sup>3</sup>.</p><h4>Treatment and prognosis</h4><p>Schwannomas are slow-growing lesions. Surgery is the treatment of choice. As schwannomas do not infiltrate the parent nerve, they can usually be separated from it. Recurrence is unusual, even after complete resection. They almost never undergo malignant change.</p>
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