Following radiotherapy for the tumor, the patient fully recovered control of the tongue.
The study, “Reversible tongue atrophy in Lambert-Eaton myasthenic syndrome,” was published in the journal Neurology.
LEMS is characterized by muscle weakness, first noticeable in the legs, which makes walking and climbing stairs increasingly difficult. As the disease progresses, the arms and shoulders are affected. But impairments also can affect the mouth, with patients developing difficulties in speech, chewing, and swallowing.
Here, clinicians report the case of a man, age 48, who was admitted to the hospital with severe limb weakness that also affected his ability to swallow, speak, and chew. The patient also showed impaired respiration and required intubation and ventilation.
His response to repeated nerve stimulation continually dropped, and his muscles were too weak to undergo further testing, namely voluntary activation and tetanic stimulation. Voluntary activation is a way to assess the neurons’ firing that produce a given force output from a muscle. In tetanic stimulation, a clinician usually stimulates a muscle with a high frequency (50–200 Hz) for five seconds.
This clinical scenario suggested LEMS, which was confirmed by further clinical examination, including blood tests that revealed the presence of antibodies against a protein called SOX1.
The patient underwent treatment with corticosteroids and Firdapse (3,4‐diaminopyridine), which helps restore communication between muscle cells. He also underwent a plasma exchange (plasmapheresis) — the temporary removal of antibodies from the blood. However, the severe muscle weakness in the mouth continued. In fact, two months after showing the symptoms of LEMS, he became unable to fully protrude the tongue and showed a marked shrinkage on both sides of the tongue.
Antibodies against SOX1 are found in a large number of patients with LEMS associated with small-cell lung cancer (SCLC). The man was later diagnosed with SCLC.
He underwent radiotherapy for the tumor and, three months later, he recovered the tongue’s function. He also had lessened tongue atrophy. The tube inserted into his windpipe (trachea) to help him breathe was removed, and he continued to improve. He recovered full tongue function by 10 months.
This study reports for the first time a case of tongue atrophy in a patient diagnosed with LEMS. It likely was the result of severe damage to the neuromuscular junction, the site where nerve cells and muscles communicate.
While “tongue atrophy uncommonly occurs in generalized myasthenia gravis,” the researchers said, it “has not been previously reported in LEMS.”
“The underlying mechanism may be neurogenic atrophy [most severe type of muscle atrophy] due to severe neuromuscular junction dysfunction,” they concluded.