A case of paraneoplastic cerebellar degeneration (PCD) and Lambert-Eaton myasthenic syndrome (LEMS) was associated with a hormone-related tumor in a patient’s oropharynx, or the middle part of the throat, according to a case report.
Although both of these neurological conditions have been linked to lung cancer, this is the first time they’ve been associated with a tumor outside the lungs, the researchers said.
The case study, “Paraneoplastic Cerebellar Degeneration and Lambert-Eaton Myasthenic Syndrome Associated with Neuroendocrine Carcinoma of the Oropharynx,” was published in the journal Internal Medicine.
LEMS is a rare autoimmune disease characterized by a malfunction of the neuromuscular junctions — the site where nerve cells and muscles communicate — leading to muscle weakness, reduced deep tendon reflexes, and problems in the autonomic nervous system, which controls involuntary functions of the body such as the heart rate.
More than 90% of LEMS patients develop antibodies against the body’s own voltage-gated calcium channels (VGCC) of the P/Q-type, a group of ion channels on the surface of cells. These autoantibodies bind to the nerve terminal at the neuromuscular junction and block the entry of calcium into the cells, which reduces the release of the neurotransmitter acetylcholine, causing muscle weakness.
These autoantibodies are also associated with PCD. Both PCD and LEMS cases are usually linked to small cell lung cancer (SCLC). “PCD-LEMS with extrapulmonary non-SCLC tumors; however, has not been previously reported,” the researchers wrote.
In this case study, the team of Japanese researchers reported for the first time a case of paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome (PCD-LEMS) in a patient with a neuroendocrine (hormone-related) tumor in the oropharynx.
The 78-year-old patient exhibited speech problems (dysarthria), difficulty swallowing (dysphagia), and muscle fatigue during walking.
Five months after presenting these symptoms, he went to a specialist with a tumor on the left side of the base of tongue and swelling of the cervical lymph nodes. He was ultimately diagnosed with small cell neuroendocrine carcinoma of the oropharynx.
After diagnosis, the patient underwent radio- and chemotherapy but he did not show any improvements in walking or reduction of muscle fatigue over the treatment period.
A neurological exam revealed he had muscle weakness in all limbs, scoring a four on the Medical Research Council scale for muscle strength, and lacked deep tendon reflexes.
Additionally, the patient lacked coordination of movement (ataxia), with a score of 13.5 on the Scale for the Assessment and Rating of Ataxia (SARA). SARA includes eight parameters and assesses disability by cumulative scoring from zero (no ataxia) to 40 (most severe ataxia).
Researchers measured the levels of the anti-P/Q-type VGCC antibodies in the patient’s blood, which were high (44 pmol/L). He was negative for other autoantibodies and magnetic resonance imaging of the head revealed no cerebellar abnormalities.
“Based on these findings, he was diagnosed as having PCD-LEMS,” the researchers wrote.
He underwent further chemotherapy treatment combined with intensity-modulated radiation therapy, which gradually improved his muscle weakness and reduced his SARA score to 6.5.
A follow-up at 16 months showed that the tumor was gone, showing no signs of malignancy, and his neurological symptoms had not worsened.
This is the first case of a patient with PCD-LEMS associated with an extrapulmonary tumor, and where cerebral ataxia responded to anti-tumor therapy, according to the researchers.
“PCD-LEMS should be considered, even in cases with extrapulmonary small-cell [neuroendocrine carcinomas], in the differential diagnosis of muscular weakness and cerebellar ataxia,” the study concluded.