University of Missouri researchers presented a rare case of Lambert–Eaton myasthenic syndrome (LEMS) that initially showed eye muscle weakness as a primary symptom in a 59-year-old woman, according to a report in the journal Cureus.
Myasthenia gravis and LEMS are two autoimmune disorders that share a common cause — an abnormal interaction between nerve cells and muscles. This is due to the overproduction and accumulation of antibodies that block nerve cells’ electrical signals, which prevents muscles cells from receiving them. However, the two disorders have different symptoms and therapy approaches.
About 59 percent of patients with myasthenia gravis have impaired functioning of the muscles around the eyes, a condition known as ocular myasthenia. In contrast, muscle weakness in patients with LEMS mostly affects the limbs, and ocular symptoms are more uncommon.
In the study “Pure Ocular Weakness as the Initial Manifestation of Lambert–Eaton Myasthenic Syndrome,” researchers highlighted the patient’s case, which was noteworthy because the main LEMS symptom was visual impairment.
The woman arrived at an ophthalmology clinic after four months of having persistent headaches, double vision, and droopy eyes. But she showed significant improvement after her eyelid muscles were stimulated with a cold ice test for three minutes.
The clinical team then tested her for blocking antibodies, but the test was negative. Based on her symptoms, she was initially diagnosed with ocular myasthenia and referred to the neurology department for further evaluation.
Physical and neurological examinations revealed that the patient had mild impairment of nerve cell electrical conductance and muscle responsiveness. Her elbow movement was particularly affected. This finding led doctors to suspect LEMS.
LEMS also is linked to cancer in about half of the cases, mostly small cell lung cancer. In this case, because the patient had a history of smoking, a chest scan was performed that confirmed the presence of a lung cancer lesion.
A new analysis of autoantibodies revealed levels about 180 times higher of calcium channel blocking antibodies, which confirmed a diagnosis of LEMS.
“Although ocular symptoms are predominantly seen in myasthenia such symptoms can also occur in LEMS,” which may make diagnosis more difficult, the researchers wrote. “Our study highlights the importance of strong clinical suspicion in diagnosing patients with LEMS,” particularly if they have a history of smoking, they added.