| Object: To investigate the value of B-scan, CDI, CT and MRIin differentiation of extraocular muscle enlargement causedby various diseases.Methods: Retrospective analysis from January 1st 2002 toDecember 31ST 2002 of imaging materials of 156 cases withenlarged extraocular muscles on CT scans.Results:1. Thyroid associated ophthalmopathy (TAO) and idiopathic orbital inflammatory pseudotumor (IOIP) CT-scan showed extraocular muscles of TAO were symmetrically enlarged with a fusiform shape. Insertion was normal in most cases, bilateral and multiple muscles involvement were more common. The margin was sharp. The frequency of specific muscle involvement in descending order were the inferior rectus, medial rectus, superior rectus and lateral rectus. Sparing tendon and a single enlarged muscle were displayed in some atypical cases. In IOIP, unilaterality, single muscle involvement, enlargement of the tendon were seen commonly. The border was usually blurred. However, bilaterality, multiple muscle involvement, sparing of the tendon were also found in IOIP. The lateral rectus was found to be most commonly involved followed by medial rectus, inferior rectus. Moderate and severe enlargement were usually observed in TAO and IOIP. B-scan showed medium-low internal reflectivity of enlarged belly in TAO and IOIP. The former had a normalinsertion and the latter had a thickened insertion. Two cases with IOIP were showed no flow signal on CDI. The enlarged muscles, compared with soft tissues, weie isointense on Ti-weighted scans and less hyperintense on T2~weighted images.2. Orbital trauma and carotid cavernous fistula (CCF) Unilateral and mild enlargement of multiple muscles were showed on CT-scan in orbital trauma and CCF. A blurred border and spared tendon were often observed. -The fracture and enlargement of superior ophthalmic vein was seen in orbital trauma and CCF, respectively. B-scan showed mild muscle belly enlargement with irregularity in the border, mild and moderate echoes in trauma. It showed no enlargement of muscle on MRI in three cases of trauma.3. Cysticercosis, intramuscular tumors, metastatic tumors, fibrous histiocytomas and a benign hemangioperic -ytoma One single marked enlarge muscle, irregular fusiform shape and thickened insertion were features on CT in the diseases of mentioned above. A hyperintense spot in low intense muscular belly was a feature on CT of cysticercosis. A thickened tendon insertion , focal heterogeneities of internal reflectivity and tapered echoes were seen on B-scan in two cases with intramuscular hemangioma. A kind of special phenomena of red and blue flood flow cycling each other was showed on CDI in a case with intramuscular venous hemangioma. Of a fibroushistiocytoraa and a benign hemangiopericytoma, the muscle and the tumor were not distinguished on IB-scan, and had a medium-low echography. Abundant flood flow signals were observed on GDI in a fibrous histiocytoma and a benign hemangiopericytoma. A low internal echo and a blurred back border were found on B-scan in two metastatic tumors. No flood flow signal was found in one case by GDI. On MRI, a case of metastatic tumors had medium-low signals in Ti-weight scan, medium signals in T2-weight scan. The another case was showed heterogeneities.4. Benign pleomorphic adenoma and adenocystic carcino -mas of lacrimal gland An enlargement mass was indistin -guished from lateral rectus on CT in cases with adenocystic carcinoma. The shape of lateral rectus muscle was basically normal basically on MRI. In benign pleomorphic adenoma, a mild ribbon-shaped enlargement of lateral rectus and insertion involved were found on CT. Both of B-scan and GDI showed no pictures of involved muscles in these two di seases.5. Venous vascular malformation, ateriovenous hemang -ioma and intraorbital spontaneous hemorrhage In one case with venous vascular malformation, medial rectus muscle was showed a marked irregularly enlargement on CT-scan, with an internal heterogeneity. Another one was dis... |
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