Screening Leads to Simultaneous Lambert–Eaton Myasthenic Syndrome and Limbic Encephalitis Diagnoses, in Unusual Case Report

A recent case report of a man diagnosed with simultaneous Lambert-Eaton myasthenic syndrome (LEMS) and limbic encephalitis (LE) highlights the need for thorough screening of patients, especially those with unusual symptoms.

The case report, titled “Paraneoplastic Lambert–Eaton Myasthenic Syndrome With Limbic Encephalitis: Clinical Correlation With the Coexistence of Anti-VGCC and Anti-GABAB Receptor Antibodies,” was published in the Journal of Clinical Neuromuscular Disease.

This case focused on a 57-year-old diabetic man with a long history of smoking, who sought hospital treatment after experiencing difficulty focusing his vision, and general weakness, for six months.

Initial tests found muscle weakness and antibodies against P/Q-type voltage-gated calcium channel (VGCC), but no evidence of cancer, and a diagnosis of LEMS was made. LEMS is the result of the body’s immune system producing antibodies against VGCC, which leads to the immune system attacking the body, resulting in symptoms like muscle weakness. The patient’s doctors planned to begin treatment with Firdapse (3,4-diaminopyridine), which can increase communication between nerve cells and muscle cells, helping to lessen LEMS symptoms.

However, before they began treatment, the patient started becoming strangely confused, and he had two seizures. LEMS doesn’t usually result in changes in cognition or seizures.

Since the treatment is itself known to increase the risk of seizures, the clinicians postponed treatment and did a more thorough examination, which included additional antibody screening and “a more aggressive search” for a tumor.

This screening led to a simultaneous diagnosis of LE, which is inflammation in the brain, specifically in the limbic system, a group of structures in the brain that, among other things, help regulate emotion. Like LEMS, LE can be triggered by the body producing antibodies against its own proteins, for example, antibodies against gamma-aminobutyric acid (GABA) receptor.

Unlike LEMS, symptoms of LE often include changes in mood, but both conditions can be paraneoplastic – meaning that they can occur as the result of a tumor, but the symptoms aren’t associated with the tumor itself.

In this patient, doctors found antibodies against GABA receptor in the fluid around his brain, and a tumor in his lung. The diagnosis was simultaneous LEMS and LE, both of which were paraneoplastic.

The patient was placed on levetiracetam, an anti-seizure medication, and his tumor was treated with chemotherapy and radiation. This controlled his symptoms for a year – though as of the publication of the report, the patient’s cancer had returned, and he was in the process of getting additional treatment.

Interestingly, there have been previous reports of patients with LEMS having antibodies against both VGCC and GABA – but these patients didn’t develop LE.

This case report highlights the need to do thorough screens, especially when patients present with unusual symptoms. In this specific case, for example, the researchers wrote,”Confusion and seizures are not part of LEMS presentation and should prompt evaluation for an alternative cause.”