3209 Ptosis: when is it not myasthenia?

• Published in: BMJ neurology open 2024-08, Vol.6 (Suppl 1), p.A56-A56
• Main Authors: Reynolds, Molly, Calma, Aicee D, Cheung, Veronica, Tan, Irene, Veitch, Elizabeth, Reddel, Stephen
• Format: Article
• Language: English
• Subjects: Diplopia; Myasthenia gravis; Poster Abstracts; Tomography
• ISSN: 2632-6140
• DOI: 10.1136/bmjno-2024-ANZAN.158

A 61-year-old right-handed female was referred for myasthenia gravis management due to right unilateral ptosis, vertical diplopia and positive icepack test. However, she also noted 18 months of progressive left lateral diplopia, new right colour desaturation and right orbital discomfort. Examination revealed right mydriasis and partial ptosis with inferior oblique, inferior recti and lateral recti weakness. There was subtle proptosis of the right eye, visual acuity was 6/7.5 bilaterally and fundoscopy normal.Routine pathology and inflammatory markers including angiotensin converting enzyme (ACE) were normal. Initial computer tomography (CT), reportedly normal, missed an infiltrative lesion within the right superior orbital fissure with erosion of the sphenoid bone subsequently demonstrated on magnetic resonance imaging (MRI). Whole body positron emission tomography (PET) revealed intense orbital apex uptake (SUV 10.8), suspicious for malignancy, and extensive high uptake lymphadenopathy elsewhere. High resolution CT chest demonstrated bilateral ground glass opacities.Orbital and transbronchial lung biopsies demonstrated non caseating granulomas, with no infection nor malignancy.This case demonstrates that sarcoidosis can cause cranial bony erosion mimicking a tumour, an uncommon isolated phenomenon. While myasthenia gravis does commonly present with ptosis, the slow progression, colour desaturation, pupillary involvement and proptosis strongly suggested an orbital apex syndrome. Clinical assumptions and imaging need to be carefully reviewed in such cases.