Abstract
Purpose
To evaluate the radiographic volume change in extraocular muscles (EOM) following orbital wall decompression for Nunery type 1 and type 2 thyroid-associated orbitopathy (TAO).
Methods
Medical records of 31 orbits in 20 patients undergoing postoperative orbital CT after orbital decompression for TAO were retrospectively reviewed. The patients were divided according to Nunery classifications. A type 1 classification was assigned to patients who had no diplopia and essentially normal versions. A type 2 classification was assigned to patients with restrictive motility loss and diplopia within 20 degrees of the primary position. EOM volumes were determined by the summation of each EOM's cross-sectional areas in the coronal plane of the CT scans and multiplying the sum by the slice thickness. Main outcome measure was a comparison of EOM volume changes between types 1 and 2 TAO and a relationship between EOM volume and change in proptosis.
Results
In type 2 TAO, a significant increase in the volume of the medial rectus muscle, lateral rectus, and total EOM was detected postoperatively (p = 0.044, 0.022, 0.049), whereas no significant changes were found in the EOM's volume changes in type 1 TAO. The reduction of proptosis after orbital decompression in type 1 TAO was significantly greater than in type 2 TAO (p = 0.025). A significant positive association was observed between the preoperative EOM volumes and the reduction of proptosis following orbital wall decompression (r = 0.505).
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![]() | Figure 1.(A) Orbital CT scan for a patient who had orbital decompression of both orbits. The medial rectus, inferior rectus, lateral rectus, and superior rectus group in the left side was outlined on coronal view. (B) Postoperative coronal CT of same patient documenting postoperative bilateral enlargement in cross-sectional area of medial rectus, inferior rectus, lateral rectus, and superior rectus. |
![]() | Figure 2.(A) The relationship between the changes in medial rectus muscle volume (postoperative-preoperative in ml) and the preoperative medial rectus muscle volume in ml. (B) Type 1 C. Type 2. |
![]() | Figure 3.(A) The relationship between the preoperative total extraocular muscle volume (in ml) and the changes in proptosis (postoperative-preoperative in mm). (B) The relationship between the changes in total extraocular muscle volume (postoperative-preoperative in ml) and the changes in proptosis (postoperative-preoperative in mm). |
Table 1.
Demographic data of Nunery type 1 and type 2 patients
Table 2.
The preoperative and postoperative volume (ml) of the rectus muscles following orbital decompression
CT measure |
Type 1 (n = 11) |
Type 2 (n = 20) |
||||||
---|---|---|---|---|---|---|---|---|
Pre-operative | Post-operative | Change* | p-value | Pre-operative | Post-operative | Change* | p-value | |
MR | 0.63 ± 0.11 | 0.84 ± 0.4 | 0.21 ± 0.42 | 0.085 | 1.06 ± 0.52 | 1.32 ± 0.49 | 0.26 ± 0.32 | 0.022 |
LR | 0.48 ± 0.32 | 0.55 ± 0.31 | 0.07 ± 0.17 | 0.225 | 0.71 ± 0.44 | 0.82 ± 0.43 | 0.11 ± 0.13 | 0.049 |
IR | 0.71 ± 0.17 | 0.77 ± 0.27 | 0.06 ± 0.16 | 0.593 | 1.27 ± 0.44 | 1.30 ± 0.46 | 0.03 ± 0.21 | 0.866 |
SRG | 0.53 ± 0.16 | 0.57 ± 0.22 | 0.04 ± 0.15 | 0.768 | 0.86 ± 0.43 | 0.88 ± 0.32 | 0.02 ± 0.20 | 0.851 |
Total EOM† | 2.35 ± 0.58 | 2.73 ± 1.04 | 0.38 ± 0.66 | 0.247 | 3.89 ± 1.51 | 4.32 ± 1.37 | 0.42 ± 0.61 | 0.044 |