Prevalence of Myasthenia Gravis in Patients Presenting to Neuro-Ophthalmology Clinic for Evaluation of Ptosis
Authors: Laura Donaldson, Mariam Issa, Victoria Dezard, Edward Margolin.
Author Disclosure Block: L. Donaldson: None. M. Issa: None. V. Dezard: None. E. Margolin: None.
Purpose: While most concerning underlying causes of ptosis such as third nerve palsy and Horner’s syndrome can be ruled out by normal pupillary and ocular motility examinations, myasthenia gravis (MG) can also present with ptosis. The incidence of ocular myasthenia gravis (OMG) in patients with isolated ptosis, however, is unknown. We reviewed all patients presenting to tertiary neuro-ophthalmology practice with ptosis of unknown etiology to determine the incidence of MG.
Study Design: Retrospective chart review
Methods: This is a retrospective study of all patients over 18 years of age presenting to a single, tertiary centre Neuro-ophthalmology practice between 2014 and 2021 with unclassified ptosis. Detailed data was extracted including patient demographics, referring physician, presenting ocular and systemic features, clinical signs, laboratory tests and imaging investigations.
Results: 60 patients were included in the study. 28 (47%) patients had ptosis along with various abnormalities of ocular motility and/or alignment and 32 (53%) had isolated unilateral ptosis without diplopia, abnormal ocular motility, or symptoms of generalized MG (GMG). Final diagnosis was aponeurotic ptosis due to levator palpebrae dehiscence in majority (73%) of patients, while 10 (17%) were diagnosed with MG (6 with OMG, 4 with GMG). Diplopia was present in 9/10 patients with MG and 8/10 had abnormal ocular findings on clinical examination such as orbicularis oculi weakness, Cogan’s lid twitch or fatiguability of ptosis on sustained upgaze. Only one patient referred for isolated unilateral ptosis was diagnosed with OMG and this patient had orbicularis oculi weakness.
Conclusions: None of the patients with isolated unilateral ptosis and otherwise normal examination had MG. All patients eventually diagnosed with MG had diplopia or orbicularis weakness on examination. Thus, the yield of investigating patients with isolated ptosis for MG is exceedingly low.