Extracranial meningioma

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Extracranial meningiomas ~~are~~ or primary extradural meningiomas are rare location-specific type of meningioma. Ectopic location of meningiomas arise outside the dural covering of the brain and spinal cord while secondary extradural meningioma refers to intradural meningioma with extradural extension and/or metastasis.

Epidemology

Rarely menigiomas can occur extracranially from ectopically located arachnoid cell rests (2 %). Sometimes an extracranial menigioma can occur as an extension of small intracranial menigioma through skull base foramina or a diploic space. No sex predilection.

Pathology

Theories assume that extradural meningiomas arise from the meningothelial cells that were entrapped within the skull sutures or fracture lines either congenitally or post traumatic respectively. Cutaneous meningiomas are believed to arise due to defect of neural tube closure led to entrapped meningocytes in subcutaneous tissue. Other theories postulate that meningiomas can arise from multipotent mesenchymal cells.

Classification

Lang et al¹classified extracranial meningiomas as:

type I - purely extracalvarial
type II - purely calvarial
type III - calvarial with extracalvarial extension

Type II and Type III tumours were further categorized as convexity (C) or skull base (B) lesions. They also found patients with IIC or IIIC have lesser recurrence rates compared to IIB or IIIB tumours.

Location

Extracranial meningiomas can occur in multiple locations like paranasal sinuses, skin, orbit, , temporal fossa and oral cavity. Other rare sites include nasal cavity, salivary glands, scalp, and carotid artery bifurcation.

Radiographic features

They are similar to intracranial menigiomas in terms of morphology and enhancement.

CT

calcifications and intense enhancement.

hyperostosis, remodeling and expansion of the affected region of the skull with or without extracalvarial soft tissue mass

purely osteolytic skull lesions are also reported and believed to be of worse prognosis, particularly if associated with soft tissue component

MRI

Signal characteristics are similar to any meningioma ^{reference required}

T1 - hypo-intense
T2 - mixed signal intensity; calcifications appear as signal voids
C+ (Gd) - intense homogenous enhancement

MRI may detect a small intracranial component if present.

Treatment and prognosis

Wide surgical resection if possible, as incomplete removal may lead to recurrence. More liable to malignant degeneration (11%) than intradural meningioma.

Differential diagnosis

The differential diagnosis for these tumours is wide and is based on their location. but includes:

-<p><strong>Extracranial meningiomas</strong> are rare location-specific type of <a href="/articles/meningioma">meningioma</a>.</p><h4>Epidemology</h4><p>Rarely menigiomas can occur extracranially from ectopically located arachnoid cell rests (2 %). Sometimes an extracranial menigioma can occur as an extension of small intracranial menigioma through <a href="/articles/cranial-foramina">skull base foramina</a> or a diploic space.</p><h4>Pathology</h4><h5>Classification</h5><p>Lang et al<sup>1</sup> classified extracranial meningiomas as </p><ul>
+<p><strong>Extracranial meningiomas</strong> or <strong>primary extradural meningiomas</strong> are rare location-specific type of <a href="/articles/meningioma">meningioma</a>. Ectopic location of meningiomas arise outside the dural covering of the brain and spinal cord while <strong>secondary extradural meningioma </strong>refers to intradural meningioma with extradural extension and/or metastasis.</p><h4>Epidemology</h4><p>Rarely menigiomas can occur extracranially from ectopically located arachnoid cell rests (2 %). Sometimes an extracranial menigioma can occur as an extension of small intracranial menigioma through <a href="/articles/cranial-foramina">skull base foramina</a> or a diploic space. No sex predilection.</p><h4>Pathology</h4><p>Theories assume that extradural meningiomas arise from the meningothelial cells that were entrapped within the skull sutures or fracture lines either congenitally or post traumatic respectively. Cutaneous meningiomas are believed to arise due to defect of neural tube closure led to entrapped meningocytes in subcutaneous tissue. Other theories postulate that meningiomas can arise from multipotent mesenchymal cells.</p><h5>Classification</h5><p>Lang et al <sup>1 </sup>classified extracranial meningiomas as:</p><ul>
-</ul><p>Type II and Type III tumours were further categorized as convexity (C) or skull base (B) lesions. They also found patients with IIC or IIIC have lesser recurrence rates compared to IIB or IIIB tumours.</p><h5>Location</h5><p>Extracranial meningiomas can occur in multiple locations like paranasal sinuses skin, orbit, , temporal fossa and oral cavity. Other rare sites include nasal cavity, salivary glands, scalp, carotid artery bifurcation. </p><h4>Radiographic features</h4><p>They are similar to intracranial menigiomas in terms of morphology and enhancement.</p><h4>CT</h4><ul><li>calcifications and intense enhancement.</li></ul><h4>MRI</h4><p>Signal characteristics are similar to any meningioma <sup>reference required</sup></p><ul>
+</ul><p>Type II and Type III tumours were further categorized as convexity (C) or skull base (B) lesions. They also found patients with IIC or IIIC have lesser recurrence rates compared to IIB or IIIB tumours.</p><h5>Location</h5><p>Extracranial meningiomas can occur in multiple locations like paranasal sinuses, skin, orbit, temporal fossa and oral cavity. Other rare sites include nasal cavity, salivary glands, scalp and carotid artery bifurcation. </p><h4>Radiographic features</h4><p>They are similar to intracranial menigiomas in terms of morphology and enhancement.</p><h4>CT</h4><ul>
+<li>calcifications and intense enhancement</li>
+<li>hyperostosis, remodeling and expansion of the affected region of the skull with or without extracalvarial soft tissue mass</li>
+<li>purely osteolytic skull lesions are also reported and believed to be of worse prognosis, particularly if associated with soft tissue component</li>
+</ul><h4>MRI</h4><p>Signal characteristics are similar to any meningioma <sup>reference required</sup></p><ul>
~~-</ul><p>MRI may detect a small intracranial component if present</p><h4>Differential diagnosis</h4><p>The differential diagnosis for these tumours is wide and is based on their location.</p>~~
+</ul><p>MRI may detect a small intracranial component if present.</p><h4>Treatment and prognosis</h4><p>Wide surgical resection if possible, as incomplete removal may lead to recurrence. More liable to malignant degeneration (11%) than intradural meningioma. </p><h4>Differential diagnosis</h4><p>The differential diagnosis for these tumours is wide and is based on their location but includes:</p><ul>
+<li>bone metastasis</li>
+<li><a href="/articles/osteosarcoma">osteosarcoma</a></li>
+<li><a href="/articles/giant-cell-tumour-of-bone">giant cell tumor</a></li>
+<li><a href="/articles/plasmacytoma">plasmacytoma</a></li>
+<li><a href="/articles/haemangioma">haemangioma</a></li>
+<li><a href="/articles/epidermoid-cyst">epidermoid cyst</a></li>
+</ul>

References changed:

5. Tokgoz N, Oner YA, Kaymaz M et-al. Primary intraosseous meningioma: CT and MRI appearance. AJNR Am J Neuroradiol. 2005;26 (8): 2053-6. <a href="http://www.ncbi.nlm.nih.gov/pubmed/16155159">Pubmed citation</a><span class="auto"></span>

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