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Fig. 27. Rhabdomyosarcoma. Coronal post-contrast fat-suppressed T1 MRI shows a sinos nasal mass with intracranial invasion ( arrow ) that demonstrates multiple lobular compo nents with more intense peripheral enhancement suggestive of the “botryoid sign”.

Schwannoma MRI is sensitive and specific for the diagnosis of extracranial head and neck schwan nomas and should be considered the imaging modality of choice for evaluating the associated nerve of origin. 33,34 Schwannomas typically appear as ovoid or fusiform masses with high T2 signal and avid enhancement on MRI ( Fig. 26 ).

Malignant Neoplasms Rhabdomyosarcoma

MRI findings of rhabdomyo sarcoma are most helpful in staging and assessing thera peutic response. 35 In particular, multiplanar postcontrast T1 weighted sequences are useful for identifying intracranial extension ( Fig. 27 ). The presence of multiple ring enhancing components within the tumors that resemble bunches of grapes (botryoid sign) is helpful in suggesting rhabdomysarcoma. 36

Fig. 28. Maxillary alveolar sarcoma. Contrast enhanced CT with axial bone windows ( A ) and reconstructed coronal soft tissue images ( B ) demonstrate an expansile, solid mandibular lesion with extension into the orbit.

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