Tolosa-Hunt Syndrome and Idiopathic Orbital Inflammatory Pseudotumor

Tolosa-Hunt syndrome and idiopathic orbital inflammatory pseudotumor are both chronic granulomatous diseases with common clinical characteristics (painful ophthalmoplegia) and response to corticosteroid therapy. Tolosa-Hunt is characterized by inflammation of the cavernous sinus and/or superior orbital fissure, while idiopathic orbital inflammatory pseudotumor involves the orbit. There may be territorial overlap of the two entities.

Contrast-enhanced, thin-slice (axial and coronal) MRI of the cavernous sinus and fat-suppressed pre- and post-contrast images of the orbits are recommended for evaluation.

Tolosa-Hunt syndrome

Imaging may be normal or demonstrate inflammatory changes in the cavernous sinus, superior orbital fissure, and/or orbit. Suprasellar and parasellar tumor invasion of the cavernous sinus may have a similar appearance. Enlargement of the optic nerve or extraocular muscles may also bee seen. MRA may show narrowing of the cavernous portion of the internal carotid artery.

Inflammatory orbital pseudotumor

Inflammatory orbital pseudotumor most commonly involves the extraocular muscles and/or lacrimal gland. The margins are irregular and the lesion may look infiltrative, mimicking neoplasm or infection.

The most common pattern is termed myositic and involves the extraocular muscles (superior complex and medial rectus most common). The tendinous insertions are also involved, differentiating this entity from thyroid-associated orbitopathy (tendons are spared).

Isolated lacrimal gland involvement (case shown here) is the second most common pattern, with diffuse enlargement of gland in the anteroposterior dimension. Differential considerations include sarcoidosis and lymphoproliferative disorders.

Another pattern of involvement is isolated to the globe and retrobulbar orbit. There is thickened sclera with heterogeneous enhancement and variable involvement of the retrobulbar fat and optic nerve.

The least common pattern involves irregular thickening and enhancement of the optic nerve sheath. Differential considerations include optic neuritis.

A diffuse pattern may also be observed, involving several of the above patterns.

Reference

• Taylor DC. Tolosa-Hunt Syndrome. eMedicine, Mar 12, 2009.
• Wasmeier C, Pfadenhauer K, Rösler A. Idiopathic inflammatory pseudotumor of the orbit and Tolosa-Hunt syndrome--are they the same disease? J Neurol. 2002 Sep;249(9):1237-41.