Enlargement of the tensor intermuscularis muscle in Graves' ophthalmopathy. A computed tomographic and magnetic resonance imaging study
K. L. Goodall, A. Jackson, B. Leatherbarrow and R. W. Whitehouse
Department of Ophthalmology, Manchester (England) Royal Eye Hospital.
OBJECTIVE: To determine whether the tensor intermuscularis muscle (TIM),
which consists of muscle fibers in the superolateral intermuscular orbital
septum, is involved in Graves' ophthalmopathy (GO). DESIGN: The computed
tomographic (n = 24) and magnetic resonance imaging (n = 10) appearances of
the TIM were retrospectively examined in 34 patients with known GO. The
severity of GO was assessed by applying a scoring system from 0 to 3 (ie,
normal [0], mild [1], moderate [2], and severe [3]) to each of the rectus
muscles and superior oblique muscle. The severity of exophthalmos,
enlargement of the superior ophthalmic vein, and displacement of the
lacrimal gland were also recorded. RESULTS: The TIM appeared as thickening
of the septum immediately behind the globe, and it was best seen on coronal
magnetic resonance images. There was enlargement of the TIM in 19 of the 34
patients, and it was bilateral in 17. Enlargement was present only in
patients with moderate or severe involvement of other muscles (muscle
index, > 7/15), and it was significantly correlated with the muscle
index (P < .05), exophthalmos (P < .05), enlargement of the superior
ophthalmic vein (P < .005), and anterior displacement of the lacrimal
gland (P < .01). Severe enlargement of the TIM was seen in only five of
the 34 patients, and it showed a close correlation with the muscle index (P
< .005), exophthalmos (P < .001), enlargement of the superior
ophthalmic vein (P < .001), and anterior displacement of the lacrimal
gland (P < .001). CONCLUSIONS: Enlargement of the TIM in GO can be
identified on computed tomographic and magnetic resonance imaging scans. It
is invariably associated with moderate or severe involvement of other
extraocular muscles, and it correlates closely with other well-recognized
imaging features of severe GO.
