Surgery for Exophthalmos

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Surgery for Exophthalmos

• Stephanie Cordes, MD
• Karen Calhoun, MD

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Introduction

• Exophthalmos is a condition of altered thyroid
  metabolism that causes protein depositions within
  the extraocular muscles
• Graves disease is a multisystem disorder
  characterized by
• hyperthyroidism associated with diffuse
  hyperplasia of the thyroid gland
• infiltrative ophthalmopathy leading to
  exophthalmos
• infiltrative dermopathy with localized pretibial
  myxedema
• Therapy is still primarily directed at
  manifestations of the disease in a palliative
  fashion

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Pathophysiology

• Many patients are euthyroid at the time the eye
  symptoms appear, although further testing usually
  reveals dysthyroidism
• Treatment of the thyroid disease does not prevent
  the later development of orbital manifestations
  or ameliorate eye symptoms already present
• Current theory involves autoreactive T cells
  which are reactive to the TSH receptors
• Humoral immunity produces antibodies to the TSH
  receptor that are stimulatory, resulting in
  hyperthyroidism

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Pathophysiology

• Extraocular muscles are the site of the most
  clinically evident changes in these patients
• Muscles are enlarged and there is an associated
  intense proliferation of perimysial fibroblasts
  and dense lymphocytic infiltration.
• Retrobulbar fibroblasts secrete
  glycosaminoglycans which causes interstitial
  edema, these cells can also produce MHC class II
  molecules, heat shock proteins, and lymphocyte
  adhesion molecules
• Fibroblast antigen may be similar to all or part
  of the TSH receptor, representing a shared
  thyroid-eye antigen

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Pathophysiology
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Graves Ophthalmopathy

• More than 50 of patients with Graves disease
  have eye complaints, only 5 warrant intervention
• Lid retraction is the orbital symptom that is
  most likely to regress without treatment
• Proptosis usually peaks 4 to 13 months after the
  onset of the disease, and regression in the range
  of 3 to 7 mm occurs in half of the patients over
  the ensuing 1 to 3 years
• Eye involvement is bilateral in the majority of
  patients although 5 to 14 will have unilateral
  disease
• Major asymmetry of eye involvement is common,
  Graves remains the most common etiology of
  unilateral proptosis in adults

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Classification

• ATA class I - involves lid lag and appearance of
  a stare
• ATA class II - increased intraocular pressure
  leads to chemosis, excessive lacrimation,
  periorbital edema, and photophobia
• ATA class III - volume of orbital contents
  increases causing proptosis (increase of 4ml
  leads to 6mm proptosis)
• ATA class IV - extraocular muscles become
  dysfunctional resulting in decreased ocular
  mobility and diplopia
• ATA class V - corneal exposure, desiccation,
  irritation and ulceration
• ATA class VI - most severe, involves damage to
  the optic nerve leading to impairment of vision

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ATA Classification
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Patient Evaluation

• Most patients are initially evaluated by a
  medical specialist
• Full endocrinology work up is essential
• Some patients complain of symptoms of
  hyperthyroidism
• Any patient with unilateral or bilateral
  exophthalmos should be considered to have thyroid
  disease
• Increased total and free T3, total and free T4,
  reverse T3 uptake, TRH, and thyroid stimulating
  immunoglobulin
• Most patients can be shown to have some amount of
  thyroid dysfunction

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Physical Examination

• Can confirm the upper and lower eyelid
  retraction, proptosis, and other physical signs
  of hyperthyroidism
• Pathognomonic sign for Graves' ophthalmopathy is
  hyperemia over lateral rectus muscle
• Complete ophthalmologic exam should be performed
• Serial eye exams are required to monitor disease
  progress and response to therapy, they should
  measure soft tissue changes, document proptosis,
  intraocular pressure, ocular motility,
  strabismus, and visual function
• Complete head and neck exam including thyroid
  status

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Physical Examination
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Radiology

• CT scans of the orbit are essential if surgery is
  planned
• Findings include 2 to 8 fold increase in the
  extraocular muscle bodies sparing the tendinous
  portions
• Inferior and medial rectus muscles are most
  commonly involved
• Ultrasound can demonstrate thickening of all the
  extraocular muscles - used to monitor the
  response to therapy
• T2 weighted images on MRI can show active
  inflammation in the orbit, no bony detail
• Scans should include paranasal sinuses and rule
  out any significant sinus disease

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CT Scan
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Differential Diagnosis

• Most common diagnosis to consider in bilateral
  proptosis is pseudotumor cerebri
• Lymphoma of the orbit can produce proptosis
• Metastatic tumor, vascular anomaly, neurofibroma,
  and retinoblastoma can all cause unilateral
  proptosis
• Most other disease entities have only superficial
  similarities to Graves ophthalmopathy and can be
  ruled out
• Keep a high index of suspicion if the diagnosis
  is to be made in a timely fashion

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Differential Diagnosis
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Management

• Multispecialty team approach is recommended
  because of multiple organ systems involved
• Team should include - endocrinologist,
  radiologist, nuclear medicine physician,
  radiation therapist, ophthalmologist,
  otolaryngologist, and neurosurgeon
• Both medical and surgical management options for
  the treatment of Graves disease

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Medical Management

• All patients require management of their
  hyperthyroidism
• Management usually centers on the suppression of
  the thyroid activity, after euthyroid status is
  achieved for 6 months the orbital status usually
  stabilizes
• 1 to 2 of patient will develop a deterioration
  in the visual status and the treatment of choice
  is high dose steroids
• Adjunctive treatment includes lubricants,
  artificial tears, moisture chambers, and taping
  retracted eyelids if necessary
• Low dose radiation therapy has been used 20Gy in
  10 fractions for 2 weeks - patients early in
  disease process most likely to benefit

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Surgical Management

• Preoperative counseling centers on risks of
  vision motility disorders and failure to achieve
  a satisfactory result
• Considered for two stages of dysthyroid
  exophthalmos
• In the acute or subacute stages, steroids are
  used, if the patient fails to regain visual
  acuity with the steroids then surgical
  decompression is indicated
• In the late stage, when proptosis and lid
  retraction is evident then cosmetic decompression
  is indicated
• Usual functional indications for decompression
  are decreasing visual acuity, visual field
  defects, abnormal visual-evoked potentials, and
  disc edema as well as corneal exposure with
  keratitis not responsive to medical management

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Surgical Approaches
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Superior Orbital Decompression

• Involves unroofing the entire superior orbital
  wall by a craniotomy
• Neurosurgeon exposes the orbit by a frontal
  craniotomy
• After the optic nerve has been identified, the
  bony roof of the orbit is removed from just
  anterior to the optic foramen to the
  anterosuperior orbital rim
• Superior periosteum is then incised in an
  H-shaped fashion and the orbital fat allowed to
  herniate into the cranial vault
• Titanium mesh and pericranial flap are used to
  close the defect
• This approach is used for only very severe cases
  due to associated morbidity

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Medial Orbital Decompression

• Approached through the standard external
  ethmoidectomy incision or through a coronal
  forehead approach
• Ethmoidectomy approach displaces the medial
  canthal tendon and elevates the lacrimal sac out
  of its fossa
• Anterior and posterior ethmoid arteries are
  identified and clipped
• A complete ethmoidectomy is performed removing
  all the mucosa bearing septa
• Posterior ethmoid cells are removed back to the
  posterior ethmoid plate
• Medial orbital periosteum is incised
  longitudinally

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Medial Orbital Decompression
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Inferior Orbital Decompression

• Creates a large inferior orbital floor blow out
  fracture while sparing injury to the infraorbital
  nerve
• Procedure can be done through subciliary,
  transconjunctival, or Caldwell-Luc incision, but
  some authors prefer to combine the approaches for
  better visualization
• A skin-muscle flap is elevated in the lower
  eyelid and the orbital rim is visualized
• The periosteum is incised and elevated from the
  orbital floor for approximately 4 cm
• Caldwell-Luc incision is made sublabially and a
  wide antrostomy is formed

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Inferior Orbital Decompression

• Course of the infraorbital nerve is visualized
  and the bone medial and lateral to the nerve is
  removed
• The remainder of the floor is removed under
  direct visualization, 3 cm anteroposterior range
  for bone removal is safe, medially removed to
  lacrimal fossa and laterally removed to the
  zygoma
• Periorbita is incised longitudinally, number of
  incisions determined intraoperatively, 4 to 6
  usually adequate
• Fat herniates into the defects on either side of
  the nerve
• Middle meatal ostium enlarged to provide for
  ventilation and drainage of the sinus

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Inferior Orbital Decompression

• Sinus is then irrigated free of blood and Penrose
  drain inserted
• Incisions are closed in layers, avoid closing the
  soft tissue layer of the lower eyelid to prevent
  ectropion
• Procedures associated with the paranasal sinuses
  should use perioperative antibiotics
• Inferior decompression alone gives a mean of 3.5
  mm reduction in proptosis, whereas combined
  antral and ethmoid decompression has been shown
  to produce a mean of over 5 mm reduction in
  proptosis

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Inferior Orbital Decompression
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Lateral Orbital Decompression

• Approaches include coronal, direct rim incision,
  or extended lateral canthotomy
• Periosteum over the lateral orbital rim is
  exposed and incised widely
• It is elevated from the orbital side of the
  infratemporal fossa for approximately 3 to 3.5 cm
  posteriorly
• Lateral orbital rim can be cut and mobilized
  leaving its attachment to the periosteum to
  assist with closure
• Much of the lateral orbital wall can be removed
  (about 2.5 to 3.5 cm)
• Periorbita is incised and fat teased out into
  newly created space

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Lateral Orbital Decompression
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Endoscopic Orbital Decompression

• Medial and medioinferior floors of the orbit can
  be removed through a transnasal approach
• Can not decompress the orbit lateral to the
  infraorbital nerve or extensively open the
  periorbita for extrusion of fat
• May require a septoplasty for exposure
• Uncinate process is taken down and a large
  antrostomy is created opening superiorly to the
  level of the orbital floor and inferiorly to the
  roof of the inferior turbinate
• Middle turbinate is routinely resected
• Ethmoidectomy is performed and the anterior and
  posterior ethmoid arteries are identified

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Endoscopic Orbital Decompression

• Medial orbital wall is expose from the fovea
  ethmoidalis to the anterior face of the sphenoid
  sinus
• Trocar inserted through the canine fossa can
  allow visualization through the puncture while
  working through the nose
• Infraorbital nerve is identified and mucosa
  elevated from the roof of the maxillary sinus
• Lamina papyracea is fractured and removed to the
  level of the ethmoid arteries, bone removal is
  carried superiorly to within 2 mm of the fovea
  ethmoidalis, posteriorly to the face of the
  sphenoid, and laterally to the nerve

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Endoscopic Orbital Decompression

• A buttress of bone is preserved anteriorly at the
  juncture of the inferior and medial orbital walls
  to avoid excessive inferior displacement of the
  globe
• Orbital periosteum is incised superiorly in a
  posterior to anterior direction with a sickle
  knife taking care to avoid excessive penetration
  with the knife
• Orbital fat protrudes into the ethmoid cavity
• Silastic splint is placed to avoid postoperative
  adhesions and packing is not used
• Endoscopic approach allows a mean reduction of
  proptosis of 3 mm

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Endoscopic Orbital Decompression
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Orbital Fat Removal

• Recently proposed as alternative to decompression
  surgery
• Utilizes subciliary and upper lid crease
  incisions
• Fat compartments are debulked from upper and
  lower lids similar to a blepharoplasty
• Must achieve excellent hemostasis, usually with
  bipolar cautery
• As much as 6 mm of proptosis reduction can be
  achieved with this approach

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Treatment Options
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Complications

• If allowed to progress unchecked, patients can
  develop progressive optic neuropathy which can
  lead to blindness
• Major complications of medical management is the
  failure to recognize a medical failure and to
  delay surgery
• Steroid therapy complications - gastric ulcer,
  irritable personality, reactivation of dormant
  infection
• Radiation complications - cataracts, pituitary
  suppression, and optic fibrosis
• Decompression surgery - diplopia, unsatisfactory
  result, corneal abrasion, excessive retraction on
  the globe, retrobulbar hematoma, injury to
  infraorbital nerve, ectropion, retinal hemorrhage
  (diabetic patient), and orbital cellulitis

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Complications
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Emergencies

• Retrobulbar hematoma, retinal vascular occlusion,
  and corneal ulcer are the major sight threatening
  emergencies
• Retrobulbar hematoma is treated with opening of
  skin incisions and evacuating the clot
• Retinal vascular occlusion is related to
  increased intraocular pressure and is an
  ophthalmologic emergency
• Patient should be maintained on appropriate eye
  protection to avoid corneal ulceration
• Patient should be warned to seek immediate
  medical attention for increasing pain in the eye
  or for decreasing vision