Download Degree of Enhancement in Extraocular Muscles in Patients

Degree of enhancement in extraocular muscles
in patients with hyperthyroidism on contrast enhanced MRI
T. Taoka, S. Iwasaki, H. Nakugwa, A. Fukusumi, K. Takayama,
M Sakamoto, T. W a h , K Kichikawa, H. Ohishi
Department. of Radiology, Nara Medical Universig, Nara, Japan
ABSTRACT: Our purpose is to evaluate the degree of
enhancement in EOMs in patients with hyperthyroidism.
We examined EOMs of 17 patients with hyperthyroidism
(including 3 patients with hypertrophy of EOMs and
exopthalmus, 8 patients without hypertrophy of EOMs but
with exopthalmus , and 6 patients without exopthalmus )
and 10 normal volunteers using fat suppressed contrast
enhanced MRI. Degree of enhancement in EOMs was
highest in normal volunteers and decreased in the order of
patients without exopthalmus, patients without
hypertrophy of EOMs but with exopthahnus and lowest in
patients with hypertrophy of EOMs and exopthalmus.
PURPOSE: Extraocular muscles (EOMs) are known for
their extremely rich capirally dstribution and their
characteristic enhancement pattern on MRI. Our purpose
is to evaluate hemodynamics of EOMs in patients with
hyperthyroidism using fat suppressed dynamic contrast
enhanced MRI.
MATERIALS and METHODS: We examined EOMs of
17 patients with hyperthyroidism and 12 normal
volunteers. Patients with hyperthyroidism consist of
various statuses as follows.
1) EOM hypertrophy (-), Exopthalamus(-)
2) EOM hypertrophy (-), Exopthalamus(+)
3) EOM hypertrophy (+), Exopthalamus (+)
The imaging sequence was fast spin echo (TR=350 ms,
TE=20 ms, ET=2) with chemical shift selective fat
saturation. Images were acquired before and 30, 60, 90,
120, 150 and 180 seconds after administration of
Gadolinium-DTPA (0.1 mmolKg). We quantified the
maximum enhancement ratio of each EOM and got the
ratio to that of temporal muscle (EOM to temporal muscle
ratio). We compared EOM to temporal muscle ratio of
superior rectus, lateral rectus, medial rectus and inferior
rectus muscle among hyperthyroidism patients with
various status and normal volunteer.
RESULTS: We show EOM to temporal muscle ratio for
each muscle in normal volunteers and patients with
various status of hyperthyroidism (Table). For each EOM,
there was a trend that EOM to temporal muscle ratio
decrease in the order of normal, patients without
exopthalmus, patients without hypertrophy of EOMs but
with exopthalmus and patients with hypertrophy of EOMs
and exopthalmus (Figure).
EOM to temporal muscle ratio in patients with overall
hyperthyroidism and normal volunteer were 1.38
(SD=0.22) and 1.80 (SD=0.38) for medial rectus muscle.
In the same order, EOM to temporal muscle ratios were
1.27 (SD=0.24) and 1.50 (SD=0.25) for inferior rectus
muscle, 1.32 (SD=0.20) and 1.57 (SD=0.21) for superior
rectus muscle, and 1.23 (SD=0.20) and 1.51 (SD=O.16) for
lateral rectus muscle. There were statistically significant
differences between patients with EOM hypertrophy and
normal volunteers in medial rectus inferior recrtus and
lateral rectus muscle.
© Proc. Intl. Soc. Mag. Reson. Med. 10 (2002)
Hyperthyroidism
bedial
I
I
1.80
ectus m. (0.25)
Superior
ectus m. (0.21)
ateral
bectus m. I (0.16) 0.23) l(0.20) l(0.08)
Table: Mean (and S1 I of EOM to temuoral ratio for each EOM
in normal volunteers and patients with various status of
hyperthyroidism.
I
CONCLUSIONS: Degree of extraocular muscle
enhancement in patients with hyperthyroidsm tended to
decrease, especially in the cases with EOM hypertrophy,
suggesting impaired circulation and reduced interstitial
space because of edema, hypertrophy of connective tissues
or perivascuritis within extraocular muscles. Since
histological evaluation is difficult in this benign disorder in
clinical cases, degree of enhancement which seems to
reflect hemodynamics and tissue changes of extraocular
muscles will be useful in evaluating severity or clinical
course of thyroid opthalamopathy.
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Figure: EOM to temporal muscle ratio for medial rectus
muscle in normal volunteers and pabents wlth various status of
hyperthyroidism