Keywords Middle turbinate - orbital decompression - thyroid eye disease
Introduction
Orbital decompression for thyroid eye disease (TED) is performed to increase the boney
orbital volume to accommodate the pathologically expanded orbital soft tissues. Traditional
indications for orbital decompression include compressive optic neuropathy (CON) or
extreme proptosis producing disfigurement or corneal exposure.[1 ] Orbital decompression may be customized to account for the unique patient's anatomy,
orbital pathology, and surgical goals.[2 ] The endonasal endoscopic approach to medial orbital decompression provides excellent
visualization of the medial aspect of the orbit, including the apex and floor medial
to the infraorbital nerve, without the need for an external incision. In the standard
surgical approach, the ethmoidal air cells and lamina papyracea are removed in addition
to the medial aspect of the floor.
To maximize the decompressive effect of a two-wall approach (medial wall and floor),
we have previously advised removal of the posterior ⅔ of the orbital strut.[3 ] We now describe the addition of a middle turbinectomy to further augment the medial
expansion of orbital contents, and, in turn, the decompressive outcome. Middle turbinate
resection (MTR) is commonly performed during endonasal endoscopic sinus and skull
base surgery for inflammatory and neoplastic disorders. While the increase in orbital
contents expansion after standard endoscopic decompression has been well established,[3 ]
[4 ]
[5 ]
[6 ] adjunctive MTR to maximize medial wall decompression has not previously been described.
In addition to improved visualization, MTR may allow additional expansion of orbital
contents into the ethmoid bed.
Herein, we present a volumetric analysis of the orbital soft-tissue expansion into
the ethmoid bed after endoscopic medial wall decompression with MTR to quantify the
volume of expansion into space previously occupied or obstructed by the middle turbinate.
Methods
Institutional Review Board approval was obtained for this Health Insurance Portability
and Accountability Act compliant study, which adheres to the tenants of the Declaration
of Helsinki. A retrospective review of patients who underwent endoscopic medial wall
decompression with MTR between July 2019 and April 2020 was performed. All endonasal
surgeries were performed by a single surgeon (D. G.) and additional orbital surgeries,
including lateral wall decompressions and upper eyelid retraction repair, were performed
by M. K. The inclusion criteria were patients with thyroid eye disease in the active
or quiescent phase, and patients with pre and postoperative orbital computed tomography
(CT) imaging available. The exclusion criteria were patients who had previous endonasal
surgery.
Surgical Technique
The surgery begins with ipsilateral comprehensive endoscopic sinus surgery, including
a maxillary antrostomy, sphenoid sinusotomy, total ethmoidectomy, and frontal sinusotomy.
Next, a curved endoscopic scissor is used to resect the entire middle turbinate from
the axilla to the basal lamella up to its skull base attachment, with the curve of
the scissor aimed inferiorly to avoid skull base injury as the dissection proceeds
posteriorly. Care should be taken to avoid injury to the olfactory region and skull
base. Suction monopolar cautery is used for hemostasis at the basal lamella arterial
branch of the sphenopalatine artery. Next, the mucosa overlying the medial orbital
wall is removed, and curettes are used to fracture and remove the lamina papyracea
and orbital floor medial to the infraorbital canal. In some patients, a 4-mm diamond
burr drill is then used to resect the orbital process of the palatine bone as well.
Next, a disposable Beaver blade and arthroplasty meniscus blade are used to incise
periorbita. A ball-tipped maxillary ostium seeker is used to separate the periorbita
from the orbital fat and muscle, and grasping forceps are then used to remove the
periorbita.
Image Analysis
Imaging software AW (GE Healthcare, Chicago, IL, USA) was used to overlay pre- and
postoperative orbital CT scans in the axial and coronal planes. The window level (0–100%)
of each scan was adjusted to visualize the preoperative position of the middle turbinate
and the postoperative orbital soft tissue that had prolapsed into the ethmoid sinus
([Fig. 1 ]). The imaging software Vitrea (Vital Images Inc., Minnetonka, MN, USA) was used
to manually segment postoperative scans to determine the volume of orbital tissue
which had filled the space previously occupied by or medial to the middle turbinate.
Only orbital tissue within the space of the middle turbinate or medial up to the nasal
septum was included in the volume analysis ([Fig. 2 ]). Volumetric analysis was performed on each segmented side individually ([Fig. 3 ]).
Fig. 1 Patient 3. Fusion of pre and postoperative orbital computer tomography scans. (A ) Preoperative coronal computer tomography. (B ) Postoperative coronal computer tomography after bilateral medial wall decompression
and middle turbinate resection. Note herniated orbital soft tissue up to the nasal
septum. (C ) Fusion of pre and postoperative scan, each at 50% opacity.
Fig. 2 Patient 4. (A ) Fusion of pre and postoperative coronal computer tomography scan. (B ) Red shading represents volumetric segmentation of small amount of orbital soft tissue
prolapsed into the space previously occupied by the right middle turbinate. Note that
no orbital soft tissue has prolapsed into this space on the left. (C ) Sagittal view of orbital soft tissue within the space of the resected middle turbinate,
shaded in red.
Fig. 3 Patient 1. (A ) and (B ) Postoperative coronal computer tomography showing volumetric segmentation of orbital
soft tissue within the area of the resected middle turbinate on the right and left,
shaded in blue. (C ) 3D reconstruction of orbital soft tissue within the space of the resected middle
turbinate and volumetric analysis showing ∼ 1.74 cc of volume in this region on the
right, shaded in blue.
Comparisons of middle turbinate volume were made using the Mann-Whitney U test.
Results
Nine orbits from 5 patients were included in this study. All patients were female,
with an average age of 55.6 years (range 32–74). Patient demographics are displayed
in [Table 1 ]. All patients had a history of hyperthyroidism and were euthyroid at the time of
surgery. Indications for decompression included CON (40%), as evidenced by visual
acuity, pupillary reactions, color vision, and Humphrey visual field testing, and
excessive proptosis with corneal exposure/ulceration (60%). Patients had a combination
of orbital fat and extraocular muscle enlargement. All patients underwent endonasal
medial wall and floor decompression. Two patients (4 orbits) underwent concurrent
lateral wall and fat decompression. Two of five patients (both with CON) were treated
with orbital radiotherapy postoperatively and ⅘ patients were treated with steroids,
either intravenous or oral, perioperatively.
Pre and postoperative exam details are listed in [Table 1 ]. Preoperative BCVA was 20/30 or better in ⅗ patients. Two patients had decreased
acuity secondary to CON or keratopathy. Postoperatively, vision remained stable or
improved in all patients. All patients received postoperative imaging within 1 month
following surgery. The follow-up time ranged from 4 to 9 months.
Table 1
Exam and operative details
Patient
Age
(yrs)
Sex
(M/F)
Initial thyroid status
Adjunct therapy
Surgical indication
Preop BCVA
Preop Hertel
(mm)
Decompression surgery performed
Postop BCVA
Reduction in proptosis (mm)
MTR volume (cc)
1a
74
F
Hyperthyroid
ORT and prednisone
CON
20/20
22
Endoscopic
2-wall
20/20
4
1.74
1b
20/20
22
Endoscopic
2-wall
20/20
2
1.86
2a
53
F
Hyperthyroid
ORT and prednisone
CON
CF
25
Endoscopic
2-wall
20/30
6
1.23
2b
20/30
26
Endoscopic
2-wall
20/30
8
0.3
3a
32
F
Hyperthyroid
none
Proptosis
20/20
29
3-wall and fat
20/20
4
1.2
3b
20/20
29
3-wall and fat
20/20
3
0.73
4a
53
F
Hyperthyroid
Prednisone
Proptosis
20/20
26
3-wall and fat
20/25
3
0.44
4b
20/25
24
3-wall and fat
20/25
1
0
5a
66
F
Hyperthyroid
Prednisone
Proptosis/keratopathy
20/40
27
Endoscopic
2-wall
20/30
3
0
Abbreviations: BCVA, best corrected visual acuity; CON, compressive optic neuropathy
as evidenced by decreased visual acuity, decreased color vision, afferent pupillary
defect, or Humphrey visual field defect; F, female; M, male; mm, millimeters; MTR,
middle turbinate resection; ORT, orbital radiation therapy.
Patients divided into a and b for right and left orbits, respectively. Endoscopic
2 wall decompression = medial wall and floor; 3-wall = endoscopic 2 wall plus lateral
wall and fat. MTR = middle turbinate resection; cc = cubic centimeters.
Of the 9 orbits, 7 (78%) had orbital soft tissue occupying the space of the resected
middle turbinate evident on postoperative imaging. The average volume of orbital tissue
within or medial to the space previously occupied by the middle turbinate was 0.83
+/− 0.67 cc. The range of volume for the 7/9 patients with orbital soft-tissue expansion
into the middle turbinate space was 0.3 to 1.9 cc. Two orbits did not have soft tissue
prolapse into the space of the resected middle turbinate. Volume did not differ between
patients who had undergone 2 or 3-wall decompressions, p = 0.41.
The average pre-operative Hertel exophthalmometry was 25.5 mm and 25.6 mm on the right
and left respectively (range 22–29). The average postoperative Hertel exophthalmometry
was 22 mm and 22.5 mm (range 18–26). The average improvement in Hertel exophthalmometry
was 3.78 mm (range 1–8 mm) p = 0.006.
No patients suffered from any complications related to middle turbinectomy, which
may include postoperative epistaxis, cerebrospinal fluid (CSF) rhinorrhea, atrophic
rhinitis, or olfactory dysfunction.
Discussion
Endoscopic medial wall decompression for patients with thyroid eye disease (TED) is
a well described procedure with documented reduction in proptosis ranging between
2 and 6 mm for the medial wall and floor.[3 ]
[4 ]
[5 ]
[6 ]
[7 ]
[8 ] In a traditional endoscopic medial wall decompression, the medial anatomic limit
of the decompression is the middle turbinate; MTR moves this limit medially to the
nasal septum. We found that MTR in conjunction with medial wall and floor decompression
increased the volume for orbital soft tissue prolapse by 0.3 to 1.9 cc in 78% of patients.
On average, each cubic centimeter of volume expansion is associated with a proptosis
reduction of 1 mm.[9 ] Therefore, we would anticipate an average of 0.83 mm improvement above the standard
surgical results with the addition of MTR. The authors specifically segmented only
orbital soft tissue within the space of the middle turbinate, and not the volume of
the middle turbinate itself, to analyze the additional soft tissue space afforded
by MTR. Differences in orbital decompression after MTR may be related to orbital compliance,
or other patient-specific factors.
Partial middle turbinate resection is commonly performed to improve the intraoperative
view during functional endoscopic sinus surgery (FESS) and also as a treatment for
nasal airway obstruction (NAO) in patients with concha bullosa.[10 ] Middle turbinate resection remains a subject of controversy among sinus surgeons,
with proponents touting improvements in postoperative sinus patency and irrigation
access, while opponents emphasize the risk of complications.[11 ]
[12 ] While the middle turbinate does play physiological roles in air conditioning, sinus
ventilation, air filtration, and olfaction, recent literature suggests that the rate
of complications—including epistaxis, CSF leak, frontal sinus stenosis, olfactory
dysfunction, and empty nose syndrome—are low.[13 ]
[14 ]
[15 ]
[16 ] Complications of turbinate resection including atrophic rhinitis and empty nose
syndrome are more often associated with total inferior turbinectomy than with partial
MTR.[13 ]
[17 ] In a series of endoscopic tumor resections and skull base reconstructions, turbinate
resection was not correlated with nasal obstruction, poor sinonasal function or poor
sleep. Additionally, no cases of debilitating sinonasal dysfunction or empty nose
syndrome were reported.[18 ]
Middle turbinate resection has been described in endoscopic orbital decompression
but is not widely or routinely utilized.[19 ] Because MTR is an adjunct to a traditional endoscopic medial wall decompression,
we do not expect outcomes or complication rates to differ substantially from those
previously published and within surgical standards.[3 ] Differences in postoperative proptosis reduction and MTR volume may be explained
by variability in orbital soft-tissue fibrosis, which may limit the expansion of orbital
soft tissues into the surrounding open sinonasal space. Patients 2 and 4 were shown
to have side-to-side asymmetry of the volume of orbital tissue within the space of
the resected middle turbinates. This may similarly be related to differences in orbital
soft tissue compliance or variations in the amount of partial resection on the middle
turbinate on each side of the patient.
The present study has several limitations. The small sample size and lack of a control
group limit the analysis. However, 78% of the orbits in this study received augmented
volume after MTR. Therefore, these findings may apply to the larger population of
patients undergoing endoscopic medial wall decompression. Two imaging platforms were
used in this study, AW to fuse the pre and postoperative images, and Vitrea to conduct
volumetric analysis, which introduces human error. The purpose of the study, however,
was to determine whether MTR augments medial wall decompression, and not to perform
a detailed volumetric analysis. Further investigations with larger groups of patients
as well as control groups and prolonged follow-up times may allow us to characterize
the exact volume of the middle turbinate and the potential for orbital volume augmentation
and proptosis reduction after resection. Two patients (4 orbits) underwent concurrent
lateral wall and fat decompression; however, this did not significantly affect the
overall augmented volume achieved by MTR compared with those patients undergoing only
a 2-wall decompression. Additionally, 2 patients (patients 1 and 2) were within the
active phase of thyroid eye disease at the time of decompression. This also did not
affect outcomes or volumes achieved from MTR.
Conclusion
This preliminary study suggests that MTR augments the orbital volume expansion achieved
by medial orbital decompression. Middle turbinate resection may be considered as a
low-risk, useful adjunct to medial wall decompression in select patients who require
maximal decompressive effect.
