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Graves orbitopathy


Key points

  • Definition: An autoimmune inflammatory disorder affecting the orbit with leukocytic infiltration causing erythema, edema, conjunctivitis, and upper lid retraction.

  • Synonyms: Graves ophthalmopathy, thyroid orbitopathy, thyroid eye disease (TED), thyroid associated orbitopathy (TAO).

  • Classic clue: Bilateral extraocular muscle (EOM) enlargement sparing tendinous insertions, with increased retroorbital fat and exophthalmos.

  • Most common cause of proptosis in adults.

  • Compression of optic nerve (ON) may cause optic neuropathy.

  • Muscle entrapment may cause diplopia.

  • Proptosis may cause corneal ulceration.

  • Compression may cause enlargement of superior orbital vein and conjunctival congestion.

Imaging

Computed tomography features

  • Main computed tomography (CT) findings include EOM enlargement and enhancement, which is usually bilateral and symmetric.

  • Involved EOMs in decreasing frequency:

    • Inferior, medial, superior, and lateral rectus muscles.

    • Isolated muscle involvement most commonly involves superior rectus and levator palpebrae complex.

  • Classically, maximal swelling in muscle belly spares tendinous global attachment.

  • Smooth margins of involved muscles.

  • Increased retrobulbar fat volume.

  • Uveoscleral thickening.

  • Orbital apex crowding may cause dilated superior orbital veins.

  • Cerebrospinal fluid (CSF) trapping in subarachnoid space may increase diameter of ON sheath.

CT recommendations

  • Not preferred but may be the first imaging study.

    • Orbital radiation is undesirable.

Magnetic resonance features

  • Magnetic resonance imaging (MRI) T2 images demonstrate enlarged hyperintense EOMs due to edema and inflammation.

  • T2 may show increased CSF in the optic nerve sheath with a “tram track” appearance suggesting ON compression.

  • T1 with fat-saturation very sensitive to muscle enlargement.

  • MRI superior contrast makes it the best method to exclude ON compression.

    • Pseudotumor cerebri and raised intracranial pressure (ICP) may give this appearance.

  • May see superior ophthalmic vein distention.

MRI recommendations

  • Preferred imaging procedure.

  • Better at defining extent of abnormality.

  • Allows the follow-up of patients without increasing the cumulative radiation dose.

Clinical issues

Presentation

  • Upper lid retraction is most common.

  • Von Graefe sign—lid lag on infraduction (downward rotation).

  • Kocher sign—eye globe lag on supraduction (upward rotation).

  • Dalrymple sign—widened palpebral fissure.

  • Lagophthalmos—inability to close eyes.

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