Man’s reflex abnormality leads to diagnosis, treatment of LEMS
Report: Reflexes would briefly return if 54-year-old flexed his muscles
Some people with Lambert–Eaton myasthenic syndrome (LEMS) experience a phenomenon called postexercise facilitation of reflexes, where normal reflexes are initially absent but then briefly return after a muscle is flexed.
The case of a man who was diagnosed with LEMS after doctors noted postexercise facilitation of reflexes was described in The New England Journal of Medicine, in a brief report titled “Postexercise Facilitation of Reflexes in the Lambert–Eaton Myasthenic Syndrome.”
Patient experienced leg weakness after long walks
LEMS is an autoimmune disorder caused by the production of antibodies that attack voltage-gated calcium channels (VGCCs) on nerve endings. These channels normally allow calcium ions to enter nerve cells, triggering the release of neurotransmitters, or chemical messengers, that signal muscles to contract. However, in LEMS, the antibodies interfere with this process, leading to reduced signaling and symptoms like muscle weakness and fatigue.
Because the signals from nerves to muscles are impaired in LEMS, people with the condition may not show typical reflexes — for example, the leg kicking forward when the knee is hit with a soft hammer. But sometimes, if the affected muscles are tensed or flexed, the reflexes will briefly return. This postexercise facilitation of reflexes occurs because, when a person flexes their muscles, calcium flows into nerve cells, and the calcium influx can briefly restore normal reflexes.
“Postexercise facilitation of reflexes is present in a minority of patients with [LEMS],” the researchers wrote. “This facilitation of reflexes occurs because the accumulation of [calcium inside nerve cells] permits a transient bypass of the antibody effect, thereby facilitating a release of [neurotransmitters from nerve cells].”
This was the case for the 54-year-old man in this report. In the months before seeking medical attention, he had begun to experience unusual leg weakness after long walks, and then he started having trouble going up stairs and biking uphill. Upon physical examination, he didn’t have normal reflexes, but his reflexes would briefly return if he flexed his muscles — a textbook example of postexercise facilitation of reflexes.
This led clinicians to test for anti-VGCC antibodies, which was positive and ultimately led to a diagnosis of LEMS.
After the diagnosis was established, the man began treatment with Firdapse (amifampridine). Because LEMS is often associated with cancer, he also started to undergo regular cancer screenings. The researchers reported that, eight years after he began treatment, the patient was no longer experiencing any LEMS symptoms.
About the Author
