J Korean Soc Magn Reson Med.  2011 Aug;15(2):176-180. 10.13104/jksmrm.2011.15.2.176.

Bilateral Extraocular Muscle Metastasis of Nasal Rhabdomyosarcoma Mimicking a Thyroid Associated Orbitopathy: A Case Report

• Shin JH
• Lee JH
• Lim HK
• Lee HY
• Park JW
• Baek HJ
• Choi YJ
• Ahn JH
• Baek JH

• KMID: 2000068
• DOI: http://doi.org/10.13104/jksmrm.2011.15.2.176

Abstract

Metastases to the orbit usually affect the intraorbital fat and bone than the extraocular muscles. Metastasis to the extracoular muscles commonly occurs unilaterally, and diffuse enlargement of the bilateral extraocular muscles due to metastasis is extremely rare. In this report, we will describe a case of diffuse metastasis to the bilateral extraocular muscles from nasal rhabdomyosarcoma masquerading as thyroid associated orbitopathy. We will also discuss about the MR imaging findings helpful for differential diagnosis from thyroid associated orbitopathy.

Keyword

Rhabdomyosarcoma; Alveolar; Extraocular muscle metastasis; Magnetic resonance imaging (MRI); Thyroid associated orbitopathy

MeSH Terms

Diagnosis, Differential
Muscles
Neoplasm Metastasis
Orbit
Rhabdomyosarcoma
Thyroid Gland

Figure

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  Fig. 1 (a-c) Initial orbit MR. Coronal T1-weighted (a), axial T2-weighted (b) and contrast-enhanced axial T1-weighted (c) images show diffuse enlargement and mild enhancement of the extraocular muscles except the left superior and the right lateral rectus muscles with sparing of the tendinous parts. The fat plane is clearly defined between the extraocular muscles and the orbital fat. Note there is abrupt curving and nodularity of the dilated muscle belly at the tendinous portion of the left medial rectus muscle (arrow). (d-f) Follow-up orbit MR 25 days after steroid pulse therapy. In addition to marked enlargement of the extraocular muscles on coronal T1-wieghted image (d), focal nodularity of the involvement muscles are more clearly demonstrated on axial T2-weighted (e) and contrast-enhanced axial T1-weighted (f) images. (g-h) 18F-FDG PET/CT performed on the same day with the 2nd follow-up orbit MRI. An axial 18F-FDG PET/CT image (g) shows intense hypermetabolism of the thickened bilateral medial and left lateral rectus muscles (SUVmax, 6.0 - 7.4 g/mL). The coronal maximum intensity projection image (h) shows multifocal hypermetabolic areas involving the axial and appendicular skeleton from disseminated bone metastasis. Contrast-enhanced axial T2-weighted image (i) after additional chemotherapy shows remarkable regression of the metastatic tumor involving the bilateral extraocular muscles.

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