Researchers reported in a study that none of the patients who presented with isolated unilateral ptosis without other ocular pathology had myasthenia gravis (MG), demonstrating the exceedingly low yield of investigating patients with isolated ptosis for possible MG, and published their results in the European Journal of Ophthalmology.
Patients who present with ptosis are most commonly diagnosed with benign aponeurotic ptosis. However, they may also have serious underlying medical conditions, such as Horner’s syndrome, third nerve palsy, or MG.
MG affects the neuromuscular junction, leading to fatigability of the skeletal muscles and frequent fluctuations in symptoms. Most patients with MG develop the generalized disease; however, in roughly 25% to 50% of cases, patients may develop isolated ocular MG.
Read more about MG differential diagnosis
Much is still unknown with regards to the association between isolated ptosis and MG. A small study reported that 6% of patients with undifferentiated ptosis were eventually diagnosed with MG. The authors hence decided to review the clinical data of patients referred to a neuro-ophthalmology clinic for undifferentiated ptosis to establish the frequency of MG among this patient population.
The research team excluded patients with a known diagnosis of MG, Horner’s syndrome, or third nerve palsy. A total of 66 patients with undifferentiated ptosis were identified. MG was suspected by clinicians in 50% of the cases, however, the final diagnosis was benign aponeurotic ptosis in 75% of patients. The key to an accurate diagnosis includes a careful ocular examination and a detailed account of the patient’s medical history.
“In patients with isolated ptosis, absence of MG symptoms (diplopia, bulbar symptoms and proximal muscle weakness) and normal ocular motility, alignment and orbicularis strength on examination essentially rule out the diagnosis of MG obviating the need for further testing,” the authors concluded.
Donaldson L, Issa M, Dezard V, Margolin E. Low probability of myasthenia gravis in patients presenting to neuro-ophthalmology clinic for evaluation of isolated ptosis. Eur J Ophthalmol. Published online June 9, 2022. doi:10.1177/11206721221107300