Download Thyroid Ophthalmopathy

Thyroid Ophthalmopathy
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Most common cause of unilateral and bilateral proptosis in adults.
Approximately 40 percent of patients with Graves disease have or will develop
signs of thyroid-related orbitopathy.
Pathophysiology
 Autoimmune-mediated inflammation of the extraocular muscle and periorbital
connective tissue
 Early inflammatory infiltrate of the extraocular muscles, connective tissues,
and lacrimal gland is later replaced by fibrosis.
 Not clear if this is a cell-mediated or a humoral immune response
 Inflammation of the orbital soft tissues and extraocular muscles is thought to
be regulated by thyroid-stimulating hormone (TSH) receptor protein
(CD40), which may be expressed on orbital fibroblasts causing chemotaxis of
inflammatory cells in the orbit.
 Lymphocytic infiltration of the orbital tissue causes a release of cytokines
which act primarily on fibroblasts.
 Fibroblasts secrete hyaluronic acid. Doubling the hyaluronic acid content in
orbital tissue causes a 5-fold increase in the tissue osmotic load. The osmotic
damage results in muscle edema, leading to proptosis, subsequent fibrosis of
muscle fibers, and eventually tissue atrophy.
Clinical
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Graves’ disease consists of hyperthyroidism associated with goiter, pretibial
dermopathy, and infiltrative ophthalmopathy.
natural course of Graves’ ophthalmopathy is usually self-limiting but may not
correspond directly with the patient’s thyroid status.
most common finding is eyelid retraction, although the spectrum of findings is
wide, ranging from subtle lid lag to disabling diplopia, severe exposure
keratopathy, and potentially blinding optic neuropathy.
Upper lid retraction (Dalrymple sign) due to
1. Proptosis
2. sympathetic drive of the Müller muscle
3. fibrosis of inferior rectus, leading to overaction of superior rectus and
levator
4. contralateral ptosis (myasthenia).
Lid lag on downgaze (von Graefe sign)
Pseudoptosis – due to contralateral lid retraction is present.
Ptosis - levator dehiscence or concurrent myasthenia
Chemosis
periorbital edema
Altered ocular motility
Strabismus common with extraocular muscle involvement
deep glabellar rhytides caused by hypertrophy of brow depressor muscles
compensating for lid retraction.
Optic neuropathy - nerve constriction due to “cone” of inflamed muscles
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Compressive optic neuropathy is the most common cause of irreversible visual
loss secondary to thyroid-related orbitopathy.
Compressive optic neuropathy, which is characterized by painless, gradual
loss of visual function, is best assessed by pupillary abnormalities (afferent
pupillary defect in the presence of asymmetric disease), diminished color
vision, and visual field defects; in some patients, central vision may not be
affected.
Investigations
 Blood
o TFTs, Antithyroid peroxidase antibody
 US
o may show thickened muscles
 CT/MRI:
o thickened muscles – usually medial and inferior rectus.
o dilated superior ophthalmic vein.
 Histologic Findings:
o Lymphocytic cell infiltration
o Enlargement of fibroblasts
o Accumulation of mucopolysaccharides
o Interstitial edema
o Increased collagen production
Treatment
 Regulation of thyroid function does not abort eye involvement.
 Usually runs a self-limited but prolonged course over 1 or more years. Patients
also should realize that no immediate cure is available.
 Thyroid ablation with orally ingested radioactive iodine (RAI; I-131) may
exacerbate the eye disease compared to antithyroid drugs or surgical ablation.
Symptomatic
 Treat dry eyes
 Monitor for exposure
 Sleep head up to reduce oedema
Medical
 Oral steroids - reserved for patients with severe inflammation or compressive
optic neuropathy. Steroids may decrease the production of
mucopolysaccharides by the fibroblasts. Effective in temporary preservation
of vision.
 Pentoxifylline and nicotinamide may be useful. Both agents are believed to
inhibit cytokine-induced glycosaminoglycan synthesis by the retroorbital
fibroblasts.
 plasmapheresis and intravenous immunoglobulin
 Orbital radiation – for moderate-to-severe inflammatory symptoms, diplopia,
and visual loss, and in cases in which steroid therapy is contraindicated or
ineffective
o Low dose - 1500-2000 cGy fractionated over 10 d
o believed to damage orbital fibroblasts or perhaps lymphocyte
o risks: Cataract, radiation retinopathy, and radiation optic neuropathy
Surgery
 Surgical intervention is not recommended during the inflammatory stage.
 Stability of the disease should be documented for at least 6 months before any
operative correction is undertaken.
Surgical options
Lid camouflage techniques
1. Lid lengthening surgery (for mild cases)
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Upper lid retraction
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lengthening of levator aponeurosis or division of Mullers muscles
(mild 2-3mm lid retraction)
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decreases corneal exposure and can be used to camouflage mild-tomoderate proptosis.
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Most common complication - high eyelid crease
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eyelid retraction may develop in the contralateral lid (Herings Law)
Lower lid
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lengthening usually requires a spacer material,
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need 4x wider than the amount of scleral show.
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Graft materials include human acellular dermis, tarsus, and
conjunctiva from the upper lid, hard palate, and ear cartilage.
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Recurrence of retraction common, reduced by tarsorraphy and
lateral strip
2. Lateral tarsorrhaphy – alternative for lid retraction. Note that horizontal
tightening procedures (ie lateral strip) will increase scleral show, better to
combine them.
Decompression
Indications
1. a sight-threatening compressive optic neuropathy unresponsive to
immunosuppressive therapy
2. proptosis causing severe ocular surface disease
3. cosmetic appearance unlikely to be improved by lid surgery alone
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Anterior decompressions are effective in reducing proptosis.
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In compressive optic neuropathy, however, decompression along the
posterior medial wall is necessary to address apical optic nerve compression
1. Orbital fat decompresion
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indicated for predominant enlargement of the orbital fat compartment,
rather than the rectus muscles on orbital imaging
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Unlike cosmetic blepharoplasty, fat is also removed posterior to the equator
of the globe
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Combined transconjuctival and blepharoplasty incisions
2. Expansion osteotomy (originally advocated by Tessier)
3. Orbital decompression- initial treatment of compressive optic neuropath or
after failed medical treatment
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Incisions:
a.
Transorbital
i. subciliary incisions
ii. lid crease incisions (blepharoplasty)
iii. transconjuctival - provides excellent visualization of the orbital
floor and medial wall. Visualization of the most posterior
portion of the medial wall, which must be adequately removed
for treatment of compressive optic neuropathy, may be
suboptimal in this approach
iv. transcaruncular
v. Lynch incision
b. Transcranial coronal incisions.
c. transantral – sublabial incision
d. endonasal - allows the removal of the orbital floor and medial wall,
especially at the orbital apex. Visualization of the medial orbital wall is
superior to other approaches, permitting more complete medial
posterior orbital wall decompression. Access to the anterior orbital
floor is limited.
e.
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Osteotomies
o At least 2 orbital walls usually are decompressed
o Most commonly the medial wall and floor of the orbit via
transantral approach
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Sublabial incision
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excellent visualization of the floor and inferior portion of the
medial wall.
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visualization of the orbital apex, posterior ethmoids, and
lateral wall of the sphenoid sinus is difficult.
o Other options:
a. Lateral orbital wall - Lateral wall decompression does not
adequately address the medial wall of the orbit, which is
required for treatment of compressive optic neuropathy.
b. Orbital floor
c. Lateral wall + lateral part of floor (Matton)
d. Medial and lateral walls (balanced decompression – avoids
diplopia)
e. Orbital roof - transfrontal decompression has significant risk
of cerebrospinal fluid leakage, meningitis, and transmission
of cerebral pulsations to the eyes.
f. Medial wall + partial floor + partial lateral wall + fat
(Roncevic and Jackson)
g. 3-wall resection
4. 4-wall resection (combined neurosurgery)
Adjunctive surgeries
1. Strabismus surgery - goal of surgery is to minimize diplopia in primary and
reading positions
2. Blepharoplasty
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Usually last operation required.
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Conservative skin excisions only.
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Set fold lower (ie 6-7mm)
Medial wall removal should not extend above the frontoethmoidal suture. This averts
bleeding from the ethmoidal arteries and prevents cerebrospinal fluid (CSF) leaks.
When the orbital floor is removed, preservation of a strut of bone between the
ethmoid and maxillary bones may reduce strabismus from inferomedial shift in the
globe position.
Lateral wall decompression does little to relieve apical compression but helps to
reproduce proptosis.
Complications of orbital decompression include blindness, hemorrhage, diplopia,
periorbital numbness, globe malposition, sinusitis, lid malposition.
Transcaruncular approach (PRS Sept 2003)
(Above, left) Caruncle and medial conjunctiva exposed. Silk traction sutures are
placed through the tarsus of the upper and lower eyelids just lateral to the puncta. The
dotted black line indicates incision site. (Above, right) Medial incision made at the
junction of the posterior one third and anterior two thirds of caruncle. (Below,
left) Blunt dissection with tips of scissors placed firmly against the posterior edge of
the posterior lacrimal crest, revealing the plane of dissection. (Below, right) Exposure
of the medial wall of the orbit with malleable retractor protecting the globe. Orbital
retractor used to retract herniated orbital fat.
Incision at the junction of the posterior one third and anterior two thirds of the
caruncle allows passage along a natural plane between the Horner muscle and the
medial orbital septum. Horner muscle buffers this safe and bloodless plane from the
lacrimal sac.
Because dissection is carried out posterior to the lacrimal system, the canthal tendon
attachments are left intact.
The plica semilunaris should not be confused with the caruncle as this will result in
too deep a dissection plane with possible damage to the medial rectus muscle and
poor visualization secondary to herniation of orbital fat
Under direct visualization, the medial wall of the orbit was infractured with a
periosteal elevator and removed with bayonet forceps. Ethmoid air cells were
removed in a graded fashion using endoscopic instruments.
Care was taken to limit dissection inferior to the level of the anterior and
posterior ethmoidal foramina (frontal-ethmoidal suture) to avoid violating the
intracranial space and creating the potential for cerebrospinal fluid leaks.
Photograph of orbit from adult human skull depicting bony landmarks. The dashed
line marks the posterior lacrimal crest. The asterisks mark the anterior and posterior
ethmoidal foramina. The dotted line below the asterisks shows the frontoethmoidal
suture, which serves as landmark for the level of the cribriform plate. The ribbonshaped area shows the position of the inferomedial orbital strut at the
maxilloethmoidal junction. The floor of orbit medial to infraorbital neurovascular
junction is retroilluminated, demonstrating the thinnest portion of the floor of the orbit
approximately 1.5 cm posterior to the orbital rim.