2. All inflammatory diseases that affect some or all of the structures contained within the
orbit external to the ocular globe.
Inflammatory process may extend beyond the orbit, into the cavernous sinus through
the orbital apex.
OID needs to be differentiated from neoplastic and infectious diseases that may have a
similar presentation.
4. CLINICAL FEATURES
Any of the structures within the orbit may be involved, the presenting symptoms can
be quite varied, but pain is often a prominent complaint.
Involvement of the extraocular muscles – diplopia
Lacrimal gland involvement - painful superolateral orbital swelling.
Generalized orbital tissue involvement - all of the above features plus
Proptosis
Chemosis
Periorbital or lid swelling
In severe cases, blindness due to optic nerve compression.
Onset can be acute to insidious depending upon the etiology.
5. Acute inflammation - symptoms developing over hours to days
Most commonly infectious etiology.
Orbital congestion from a rapidly growing tumor may mimic orbital cellulitis and
tumor necrosis may provoke an inflammatory reaction.
A subacute clinical course is common with TAO and idiopathic orbital inflammation,
but also occurs with the systemic vasculitides.
6. TAO - The most common cause of orbital inflammation
In adults, accounting for nearly 60% of cases in the 21- to 60-year-old age
group and 40% of orbital disease in those older than 60 years
Up to 10% of patients with OID due to thyroid disease do not have Graves’
disease
7. The mean age of onset of Graves’ thyroid disease is 41 Years
Women are affected at least 3 times more frequently
Men and those with onset after the age of 50 years tend to have more severe disease
Smoking appears to significantly increase both the incidence and the severity of TAO
8. The pathophysiology of TAO - autoimmune mediated process supported by the
histopathologic findings.
Marked infiltration of lymphocytes and macrophages due to molecular mimicry
Increased production of hydrophilic glycosaminoglycans in connective tissue
surrounding the extraocular muscles, fibroadipose tissue, and enlargement of extraocular
muscles sparing tendinous insertion of muscle.
This differs from idiopathic orbital inflammation that shows more extensive lymphocytic
infiltration, including the tendinous insertion of the muscle.
9. Two stages of TAO
Characterized by an active inflammatory phase followed by the quiescent or “burnt-out” phase. The initial
period of acute inflammation lasts approximately 6 months to 2 years f/b fibrotic phase
Symptoms – Minimal pain, Dry eye, puffy eyelids, proptosis, diplopia, visual loss
Lid retraction (Dalrymple sign) – M/C ocular sign
Proptosis
Sympathetic drive of muller muscle
Upgaze restriction
Levator fibrosis
10. Anterior segment signs of TAO
Superficial punctate keratitis
Superior limbic keratoconjuctivitis
Conjuctival congestion over rectus muscle insertion
Strabismus
IR>MR>SR>LR
Optic Nerve and Fundus
Blurring of vision, visual loss, field loss
Patients with optic nerve compression may not have marked proptosis or seemingly
mild proptosis, but they show markedly decreased retropulsion ( Tight orbits )
Without visible papilloedema. Visual field, RAPD follow up is required
11.
12. Thyroid profile with anti TPO ( 10% have euthyroid status with only elevated anti
TPO )
Visual field testing periodically
MRI – more sensitive than CT scan
In TAO the characteristic finding is enlargement of the extraocular muscles that spare
the tendinous insertions.
An ordered pattern of involvement is also often seen, with the inferior rectus involved
first, followed by involvement of medial, superior, and lateral recti muscles. The
oblique muscles are rarely involved.
13. Bilateral (but not necessarily symmetrical) involvement is seen in 90%
Other findings include an increased amount of intraorbital fat.
Isolated rectus muscle involvement in 6%. SR is common. Isolated LR leads towards
other diagnosis.
Signal of the extraocular muscles on MRI is also useful in predicting response to
therapy, with a low T2 signal corresponding to a more fibrotic form, which is less
responsive to therapy compared with those patients with increased T2 signal in the
extraocular muscles.
A number of authors have reported that increased extraocular muscle volume correlates
with the severity of optic neuropathy
14. Imaging of thyroid-associated ophthalmopathy.
(A) Axial FLAIR (fluid attenuated inversion
recovery) MRI showing marked bilateral
enlargement of the extraocular muscles, in
particular, the medial recti, that has spared the
tendinous insertions, resulting in the
characteristic “spindle shape.”
(B) Coronal STIR (short tau inversion recovery)
MRI of the same patient, revealing the extent of
extraocular muscle enlargement and increased
signal. There is also mucosal thickening in the
visualized paranasal sinuses.
(C) Axial T1-weighted MRI of the orbit with
contrast (gadolinium) and fat suppression further
highlighting the typical pattern of TAO muscle
enlargement and increased muscle enhancement.
Joseph R. Lutt, MD et al., 2008 [3]
15. Prisms for small deviation. Tape occlusion of 1 Lens or segment of the glasses
for diplopia
Dry eye, corneal exposure Artificial tear during day and lubricating
ointment in the night
Systemic steroids for Severe inflammation and in compressive optic neuropathy
in TAO. EUGOGO suggests 4.5 – 5 gm of MPS.
16. If no response in 48-72 hours, steroid probably won't work. Need surgical
decompression and maintenance steroid.
In case of good response to steroid, Orbital radiation can be considered.
In severe cases of TAO, combined steroid, radiation and surgery is considered.
Rituximab, cyclosporine, octreotide, IVIg less common modalities of treatment
Selenium 200mcg/day in deficient patients
RCT for above drugs showed conflicting results
17. Orbital radiation__ For moderate to severe cases along with steroid. It is
believed to damage fibroblasts and lymphocyte.
1500 – 2000 cGy fractioned over 10 days is administered via lateral field with
posterior angulation.
Need to continue steroid for few weeks till effect of radiation initiates
Better response in active inflammatory stage within 7 months of onset of TAO.
DM is a contraindication because of risk of worsening retinopathy.
18. Orbital inflammatory disease (OID, aka orbital inflammatory pseudotumor, idiopathic
orbital inflammatory syndrome, nonspecific orbital inflammation).
Gleason in 1903, accounts for 6% of diseases involving the orbit.
Third most common orbital disease after Grave’s orbitopathy and lymphoproliferative
diseases.
Commonly unilateral with symptoms and clinical findings depending on the site
involved.
Generally, acute OID presents with proptosis, extraocular motility disturbance, pain,
erythema, and chemosis
19. • Dacryoadenitis of Lacrimal glands
• Myositis of extraocular muscles
• Perineuritis of optic nerve
• Orbital cellulitis
• Orbital apicitis ( Tolosa Hunt Syndrome )
• Periscleritis
• Diffuse orbital inflammatory disease
20. Inflammation of the lacrimal gland which is commonly seen in OID.
Presents as a painful, firm, erythematous mass with edema in the lateral upper lid, and
possible ptosis.
Classic appearance is of diffuse enlargement of the gland, including the orbital and
palpebral lobes along with inflammation of surrounding tissues
Whereas epithelial neoplasm which is close D/D typically involves a portion of the
lacrimal gland, usually the orbital lobe.
21. BA
Dacryoadenitis.
A: Axial T2 shows diffuse enlargement of the left lacrimal gland. Note the tapered posterior margin (long arrow), as well as the
involvement of the orbital lobe (short arrow). These findings suggest a lymphoid or inflammatory process rather than an epithelial
neoplasm.
B: Axial fat-suppressed contrast enhanced T1 shows infiltration of the preseptal (long arrow) and post septal (short arrow) fat. These
features suggest orbital inflammatory disease rather than orbital lymphoma.
22. Adenoid cystic carcinoma of the lacrimal gland.
A: Axial T1 non-enhanced MRI showing an enlarged, heterogeneous left lacrimal gland (black arrow). Compare this to the
contralateral normal gland (white arrow)
B: Axial T1 non-enhanced MRI showing sparing of the palpebral lobe (arrows).
A B
23. Lacrimal gland lymphoma (A and B)
compared to inflammatory dacryoadenitis
(C and D).
A: DWI image in a patient with lacrimal gland
lymphoma. Note the bright signal intensity(arrow)
secondary to inhibition of water movement by the
densely packed lymphoma cells
B: The corresponding ADC map of this patient shows
an associated reduction in ADC, represented by the dark
signal just lateral to the orbit (arrow)
C: DWI image in a patient with inflammatory
dacryocystadenitis. Note the dark signal compared to
the patient with lymphoma (arrow)
D: ADC map shows bright signal in the involved
lacrimal gland (arrow) as compared to normal brain
parenchyma.
A B
C D
24. Non-infectious inflammatory condition primarily affecting the extraocular muscles
(EOM).
Presents with Unilateral orbital or periorbital pain, painful and restricted eye movement,
proptosis, periorbital edema and hyperemia of the conjunctiva.
The classic appearance of EOM myositis includes a unilateral thickening of one or two
EOMs, often also involving the surrounding fat, tendon, and myotendinous junction.
Important Differential diagnosis
1)TAO 2)IgG4 related disease 3)Lymphoma 4)CCF
Differentiation from Thyroid Disease --- Unilateral disease, infiltration of the
surrounding fat, & early involvement of the superior oblique muscle
25. A B C
A: Coronal fat-suppressed contrast-enhanced T1 shows enlarged left superior oblique (white arrow) and superior rectus (black arrow) muscles, and mild
infiltration of the surrounding fat
B: Coronal fat-suppressed T2 shows low signal in the superior oblique muscle (white arrow), suggesting a more chronic, burned out process, whereas the
superior rectus muscle (black arrow) shows brighter signal, indicative of a more acute process
C: Parasagittal oblique fat-suppressed contrast-enhanced T1 shows an enlarged superior rectus muscle belly (long arrow). The tendinous insertion (short arrow)
is uncharacteristically spared by this process. Nevertheless, unilateral disease, infiltration of the surrounding fat, and early involvement of the superior oblique
muscle indicate pseudotumor ahead of thyroid eye disease.
26. Indirect carotid-cavernous fistula.
A: Coronal T2 MRI with fat saturation demonstrating mild infiltration of orbital fat (arrowhead) and thickening with high signal intensity in the EOMs. In this
image, the lateral rectus muscle appears brightest (short white arrow). Note the enlarged SOV (long white arrow), suggesting CCF over myositis
B: Axial post-gadolinium T1 MRI with fat saturation. The SOV (long white arrow) is engorged secondary to retrograde flow from the cavernous sinus. The
superior oblique muscle (short white arrow) is also enlarged
C: Angiogram with lateral projection common carotid artery injection (patient facing to the right) showing abnormal early filling in the cavernous sinus and SOV
(short black arrows), as well as an abnormal tangle of vessels along dorsal surface of cavernous sinus (long black arrow), representing abnormally dilated
intracavernous ICA branches.
A B C
27. Inflammation of preseptal (peri-orbital) or postsetpal (orbital) fat.
Patients typically present with proptosis, chemosis, and painful diplopia.
It is best evaluated on contrast-enhanced T1 MRI with fat suppression, most common finding is poorly-
defined periorbital enhancement enveloping the globe and extending into post – septal fat.
Infectious cellulitis shares similar imaging features ---- it is important to obtain any clinical history of fever,
sinusitis, or meningitis, as well as any evidence of leukocytosis.
On T2 MRI, infectious cellulitis typically presents as a hyperintense lesion. OID lesions range from to
hypo- to hyperintense
28. Infectious orbital cellulitis.
A: Axial CT showing layering fluid in the ethmoid sinus and frontal recess on the left (black arrows), and infiltration of the orbital fat (white
arrow)
B: Coronal T1 fat saturated post-gadolinium MRI demonstrates orbital fat infiltration (long white arrow). Fluid in the adjacent ethmoid
sinus (black arrow) and intracranial extension of the process (short white arrow) are also features that indicate infection rather than
orbital inflammatory disease.A
A B
29. Diffuse cellulitic orbital inflammatory disease.
A: Coronal T1-weighted image shows diffuse infiltration of the intraconal fat on the left (arrow)
B: Axial fat suppressed contrast-enhanced T1 shows diffuse enhancement throughout the intraconal fat. No well-defined focal mass or focal fluid collection is
seen.
A B
30. Intraorbital inflammation extends along the optic nerve and nerve sheath.
Because inflammation affects the nerve sheath rather than the nerve itself, the
primary presenting clinical feature is pain, while visual acuity, visual fields and
color vision are typically unaffected.
The classic appearance is of increased signal intensity surrounding the optic
nerve, and extending into adjacent fat on post-gadolinium T1 MRI with fat-
suppression.
D/D – Meningioma ( CT scan – localised mass and calcification )
Demyelinating lesion ( Spare soft tissue around the nerve )
31. A B
Perineuritic orbital inflammatory disease.
A: Coronal fat-suppressed contrast-enhanced T1 shows circumferential enhancement about the left optic nerve (long arrow), with sparing of
the nerve substance. There is also mild infiltration of the surrounding soft tissues (short arrow)
B: Axial fat-suppressed T2 shows a small amount of edema about Tenon’s capsule (arrow). This finding, along with clinical history of
acute, painful presentation, help distinguish perineuritic pseudotumor from optic nerve sheath meningioma.
32. Meningioma of the right optic nerve
sheath.
Axial fat – suppressed contrast enhanced T1-
weighted image show a well-defined
enhancement of a localized mass in the optic
nerve sheath (“tram – track sign”) which is
characteristic for meningioma.
1-2% of meningioma
Seen in NF-2
Slow growing rare benign tumour
Gradual loss of vision in affected eye
Sx, Radiation, combination
33. Refer to inflammation of the sclera, uvea (iris, ciliary body, choroid), or
tenon’s capsule.
Characterized by orbital pain, exophthalmos, and eyelid edema and clearly
seen on MR or CT as a heterogeneous thickening along the outer rim of the
eye.
Axial T1 post-contrast MRI with fat saturation - Visualization of the enhancing
vascular choroid as well as any extension into retrobulbar fat.
D/D – Systemic inflammatory disease which causes posterior scleritis such as
SLE, RA. Infectious periscleritis secondary to sinus infection should be ruled
out.
34. Periscleritic orbital inflammatory disease.
Eighty-seven-year-old immunocompromised man with left eye pain and ordering indication of “cellulitis”.
A: Axial contrast-enhanced CT shows mild infiltration of the left periorbital fat (short white arrow). There is also periscleral edema (long
white arrow), and subtle high density along the temporal surface of the globe that is suggestive of a subchoroidal fluid collection (black
arrow)
B: Axial fat-suppressed contrast-enhanced T1 shows these findings more conspicuously. Note that the elevated choroid layer (black arrow)
extends anteriorly to the region of the ciliary body. Periscleral edema (long white arrow) extending to Tenon’s capsule is better seen.
A B
35. Focal Mass
OID may also present as a focal inflammatory mass.
Represents 9% of orbital mass.
Lymphoma accounts for 20% of focal mass. Difficult to distinguish.
OID may present with eyelid edema, optic nerve atrophy, and conjunctival congestion
while lymphomatous lesions present more commonly with palpable mass
36. Imaging features of inflammatory pseudotumor that help distinguish it from
lymphoma
OID - Marked T2 hypointensity and T1 mild hyperintensity with post
gadolinium enhancement
Lymphoma – T1 hypointensity and T2 marked hyperintensity. On DWI –
more lobular
Metastasis – Bright on T2 except Scirrhous breast cancer metastasis which is
T2 hypointense
Benign tumors, such as Solitary fibrous tumor, can also show marked T2
hypointensity and overlap with OID in appearance.
37. Orbital inflammatory
disease producing a
focal mass.
Axial T2 shows a well-
defined, T2 hypointense mass
in the right orbit, discrete from
adjacent extraocular muscles
and from the lacrimal gland.
38. Involvement of the orbital apex is less common and associated with poor
outcome.
Inflammatory lesions of the orbital apex are at risk of invading the optic nerve
early or extending into the cavernous sinus.
Extension of OID into the cavernous sinus is known as “Tolosa Hunt
Syndrome” which is characterised by
Cavernous sinus inflammation,
Relapsing/remitting acute orbital pain and paralysis of cranial nerves Ⅲ, Ⅳ,
Ⅴ1, and Ⅵ.
39. Severe retro orbital / periorbital constant pain of acute onset
Diplopia, Visual loss, Paresthesias along the forehead
Unilateral
Rare till 2nd decade
40. International headache society criteria for Tolosa Hunt syndrome
Episode(s) of unilateral orbital pain for an average of 8 weeks if left untreated
Associated paresis of the 3rd , 4th or 6th cranial nerves, which may coincide with onset
of pain or follow it by a period of up to 2 weeks
Pain that is relieved within 72 hours of steroid therapy initiation
Exclusion of other conditions by neuroimaging and (not cumpolsory) angiography
Treatment – corticosteroid. Methotrexate, azathioprine in non responsive cases.
Relapse in 40% cases.
41. Orbital apicitis
(Tolosa-Hunt).
Axial fat-suppressed contrast- enhanced T1
shows ill-defined enhancement involving the
right orbital apex, and extending into the
middle cranial fossa along the margin of the
cavernous sinus (arrow).
Common features of CNS involvement
Abnormal soft tissue extending into the
middle cranial fossa
Expansion of the ipsilateral cavernous sinus
walls
Post-gadolinium enhancement of the
meninges or dura.
42. A
B
Tolosa-Hunt syndrome,
before and after treatment.
A: Axial fat suppressed
contrast-enhanced T1 showing
bilateral cavernous sinus
infiltration and enhancing
tissue along the lateral margins
of the cavernous sinus;
B: Complete resolution after
treatment.
43. High dose steroid – Acute/Subacute OID. Dramatic response helps confirm diagnosis. Tapering should be
done over months.
Methotrexate ( 15 – 20 mg ) is been successful as a steroid sparing agent.
Cyclophopshamide - in refractory cases can be used along with steroid
MMF – role not proven
Azathioprine , cyclosporine – Trial proven role
Refractory cases – Anti TNF – alpha inhibitors. I.V infliximab, S.C Adalimumab and Etanercept
Radiotherapy
44. IgG4-related disease (RD) was first described in patients with autoimmune
pancreatitis who had high serum IgG4 levels
Male = Female. Younger age group
Since 2003, considered as a multi system disorder which involves pancreas,
biliary tree, salivary glands, kidney, lung, skin and prostate
CNS manifestations are uncommon. Hypertrophic pachymeningitis and
hypophysitis are frequent manifestations. Commonly occurs in conjuction
with other system involvement
45. In Orbit, it involves Lacrimal glands > Extraocular muscles > Adipose tissue
C/F - Painless unilateral or Bilateral periorbital swelling, erythema due to
lacrimal gland involvement
EOMs – IR > SR – levator complex > LR > MR > IO > SO . EOM
involvement is less common than TAO.
Compressive optic neuropathy – less common
Epiphora due to nasolacrimal duct involvement
Salivary gland enlargement
46. Diagnostic criteria IgG4 ROD (2015) by Goto et al.
Imaging studies show enlargement of lacrimal gland, trigeminal nerve or extraocular muscle as
well as masses, enlargement or hypertrophic lesions in various ophthalmic tissues
Histology examination shows marked lymphoplasmacytoid infiltration and storiform fibrosis.
Ratio of IgG4+ cells to IgG+ cells of 40% or above, or more than 50 IgG4+ cells/HPF
Blood test shows elevated serum IgG4 ( >= 135 mg/dl)
Treatment – Corticosteroid. Relapse rate has been reported as high as 70%. Treatment of
relapse involve 6-10 week of steroid or rituximab. Relapse is seen also with rituximab after 6
months
Poor outcome with MMF, Azathioprine and Radiotherapy
47. IgG4-related disease.
Axial post contrasted enhanced
T1 – Weighted image with fat –
suppression displays the typically
affected bilateral lacrimal gland
and left inferior rectus muscle.
48. Sarcoidosis is an idiopathic, multisystem inflammatory disorder characterized
by noncaseating granulomas.
Ophthalmic disease occurs in 25 to 50% of patients with sarcoidosis among
which Anterior and posterior uveitis are common.
Sarcoid infiltration of the orbit is less common which is present in
approximately 1/4th of cases with ocular involvement and up to 10% of all
patients.
Generally limited to the lacrimal glands. When extralacrimal gland
involvement is present, it is almost always unilateral.
49.
50. Presentation is same as other OIDs like pain, ophthalmoplegia, proptosis and
later diminished vision.
The symptoms of sarcoidosis tend to wax and wane. Spontaneous remissions
are not uncommon.
Diagnosis is made with the help of other organ involvement
ACE level doesn’t help without pulmonary involvement. Chest CT has been
reported to be far more sensitive than chest radiography or ACE levels for
sarcoidosis
51. Confirmed diagnosis usually requires pathologic evidence of noncaseating
granulomatous inflammation as well as the exclusion of other possible
granulomatous diseases.
Treatment - Corticosteroid
In refractory, steroid-dependent or steroid intolerant cases, methotrexate,
azathioprine, and infliximab have proven useful
52.
53. Churg– Strauss syndrome ( Rare case reports )
Polyarteritis nodosa ( 10 cases of Orbital PAN has been reported )
Giant cell arteritis ( Rare case reports )
WG has a special predilection for orbital tissue which is a small- and medium-sized
vessel vasculitis
Ophthalmic disease affects 28 to 58% of patients at some point in the course of WG
and is present as a part of the initial symptom complex in 8 to 16% of patients.
54. Orbital inflammation along with episcleritis, scleritis, or uveitis is common than retinal
vasculitis
Involvement of the orbit is thought to result from either continuous spread from the
sinuses or secondary to a primary vasculitic process. Diffuse orbital involvement is
common.
Bilateral eye pain, proptosis, erythema, and motility restriction are common clinical
features
Proptosis is a poor prognostic sign, with half of patients in 1 series subsequently losing
vision due to optic nerve ischemia.
55. ANCA can have a high positive predictive value for this disease in patients with a
symptom complex suggesting WG
Sensitivity and specificity for c-ANCA with antibodies directed toward proteinase 3
(PR3) is between 80 and 100%
Since greater than 30% of patients with limited WG, in which the kidneys are spared,
will not have ANCA positivity, it should not be used to rule out WG.
Hence, confirmed diagnosis can be done on basis of biopsy
56. The diagnosis of WG is usually based on histological findings in a compatible clinical
setting.
The classic histopathological triad
1)granulomatous inflammation
2)Tissue necrosis
3)vasculitis involving arteries, capillaries,and veins.
Nearly all patients who underwent orbital biopsy in 1 small series had evidence of
necrosis and granulomas [1]
Necrotizing vasculitis appears to be less common, occurring in less than one-third of cases
Perry SR, Rootman et al., 1997 [1]
57. Granulomatosis with
polyangiitis
T1 weighted MRI of orbit with
gadolinium infusion and fat
suppression
A: Image showing a mass
involving right orbital space and
extending into the ethmoid sinus.
The mass is displacing the globe.
A small mass is also shown in left
orbital space
B: Image showing reduction in
mass after 12 week of treatment
58. Remission – Corticosteroid, Methotrexate, Cyclophosphamide, Rituximab
Maintenance – Azathioprine, Methotrexate, leflunomide, Rituximab
The treatment of limited WG is typically less aggressive than that of life-threatening
pulmonary or renal disease with corticosteroid
More aggressive therapy is reserved for those with potential optic nerve compromise with
combination of high dose corticosteroid and cyclophosphamide
Rituximab vs Azathioprine in maintenance therapy [1]
Guillevin L et al., Rituximab versus Azathioprine for maintenance in ANCA-associated vasculitis.N Engl J Med.2014;371(19):1771-1780 [1]
59. Recently, a remarkable treatment response with the use of rituximab, an anti-CD20
monoclonal antibody observed in resistant disease.
The largest of several small case series involving patients with WG included 11
patients whose disease was refractory to maximally tolerated cyclophosphamide and
glucocorticoids
Three of these 11 patients were reported to have ocular involvement and all 11 had
disease remission within 6 months. [1]
Keogh KA et al., Induction of remission by B lymphocyte depletion in eleven patients with
refractory antineutrophil cytoplasmic antibody-associated vasculitis. Arthritis Rheum 2005 [1]
60.
61. Rare causes of OIDs
Xanthogranulomatous disease
Adult-onset xanthogranuloma (AOX)
Adult-onset asthma and periocular xanthogranuloma (AAPOX)
Necrobiotic xanthogranuloma (NBX)
Erdheim–Chester Disease (ECD)
Castleman’s disease
Kimura’s disease and angiolymphoid hyperplasia with eosinophilia
Melkersson–Rosenthal syndrome
Rosai–Dorfman disease
Need biopsy to confirm
Myositic pseudotumor. A: Coronal fat-suppressed contrast-enhanced T1 shows enlarged left superior oblique (white arrow) and superior rectus (black
arrow) muscles, and mild infiltration of the surrounding fat; B: Coronal fat-suppressed T2 shows low signal in the superior oblique muscle (white arrow), suggesting a
more chronic, burned out process, whereas the superior rectus muscle (black arrow) shows brighter signal, indicative of a more acute process; C: Parasagittal oblique
fat-suppressed contrast-enhanced T1 shows an enlarged superior rectus muscle belly (long arrow). The tendinous insertion (short arrow) is uncharacteristically spared
by this process. Nevertheless, unilateral disease, infiltration of the surrounding fat, and early involvement of the superior oblique muscle indicate pseudotumor ahead
of thyroid eye disease.