How Lambert-Eaton myasthenic syndrome presents around the eyes

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of the neuromuscular junction, and some patients first turn up in an eye care practice with drooping eyelids and double vision. Because it can look much like myasthenia gravis on examination, recognizing it early can make a meaningful difference for patients.

Alfredo A. Sadun, MD, PhD, a neuro-ophthalmologist who holds the Flora L. Thornton Endowed Chair at Doheny Eye Centers-UCLA and serves as vice chair of ophthalmology at UCLA, spoke with Ophthalmology Times about what LEMS is and how it presents around the eyes.

What sets LEMS apart from myasthenia gravis?

Sadun said he teaches LEMS by starting with myasthenia gravis, an autoimmune failure at the neuromuscular junction that is not common but not exceedingly rare either. LEMS is also autoimmune, but it is extremely rare and is connected to a cancer, which makes it a much more dangerous condition.

"The distinction from the clinical presentation can be very hard to make," Sadun told Ophthalmology Times. "So it can look very much like myasthenia gravis."

Strictly speaking, LEMS does not involve the eyeball itself but the muscles around the eye, he explained. As in myasthenia gravis, the eyelids and eye movements are the most common site of muscle weakness in the entire body. "In both cases, the patient, about 90% of the times, comes to you with the complaint that one lid or both lids are drooping," he said.

How do the eye findings present?

Variability is the hallmark of both diagnoses, according to Sadun. Patients may report that a lid droops by late morning, or not until evening, and that the problem comes and goes. Weakness accumulates as the day goes by, as the patient becomes generally fatigued, and as the clinician keeps stressing the muscle being measured. Sadun illustrated the point with a teaching joke in which each successive examiner, from medical student to resident to fellow to Sadun himself, measures more lid droop than the last.

"The more we play with the eye, the more we fatigue it, the worse it gets," he said.

Double vision is the other common complaint, and it has nothing to do with the optics of the eye. Muscle weakness keeps one eye from moving as far as the other. If the muscle that lifts the right eye is affected, for example, the left eye goes all the way up during upgaze while the right eye goes only halfway, the eyes fall out of alignment, and the brain perceives 2 images.