Painless Orbital Pseudotumor With Levator Palpebrae and Superior Rectus Muscle Swelling in MRI

Abstract

Background & Significance: Orbital pseudotumor, also known as idiopathic orbital inflammatory syndrome (IOIS), is a heterogeneous group of disorders characterised by orbital inflammation without any identifiable local or systemic causes. It is a rare clinical entity and a diagnosis of exclusion. Common clinical manifestation is a mixture of infiltrative and inflammatory signs and symptoms, including swelling, pain, proptosis, diplopia, decreased vision and ptosis. We experienced a case of “painless” orbital pseudotumor, which was diagnosed by orbital CT and MRI with good response to steroids.

Case: A 32-year-old woman was admitted to the hospital with recurrent onset of painless left ptosis, upper eyelid swelling and diplopia. There were 2 episodes (6 years ago and 1 year go) of migraine-like headaches accompanying left ptosis, eyelid edema and diplopia before admission. Thereafter, she was treated with systemic corticosteroids, which resulted in dramatic improvement of symptoms within 4-6 weeks for both episodes. Upon neurological examination, we found moderate limitation of left eye movement, especially abduction, but visual acuity and pupillary reflex was normal. She complained of diplopia, but there was no ocular pain or headache. Serum level of ASO was slightly increased. Other than such, there were no clinical and serological evidences of collagen vascular disease and Grave’s disease. Plain and contrastenhanced CT scan of orbit showed diffuse-enhanced thickening of left levator palpabrae muscle. Orbital MRI also showed gross enlargement of left superior rectus muscle and levator palpabrae muscle, and such enlargement was extended to muscle tendon junctions. Low signal intensity was present on this lesion in T2 weighted images and left upper eyelid was enhanced with gadolinium. We were able to diagnose her case as orbital pseudotumor by imaging techniques, and decided to start the systemic corticosteroid treatment, to which clinical symptoms have shown good responses.

Conclusions or Commentes: IOIS is an unusual inflammatory condition established by typical clinical and imaging findings. The presenting symptoms are usually acute with accompanying pain, photophobia, proptosis, eyelid swelling, chemosis, conjunctival injection, double vision and, less commonly, vision loss. IOIS is more likely to be abrupt on the onset and painful than other inflammatory conditions. However, it may also be present without pain. We are reporting a case of painless orbital pseudotumor which involves superior rectus muscle and levator palpabrae muscle with relapsing pattern. “Painless” indicates that painless orbital pseudotumor should not be ruled out in the case of “painless ophthalmoplegia.”