Paraneoplastic neurological syndromes, a diverse group of neurological syndromes, are associated with small cell lung, testicular, ovarian, and breast
cancers; however, their association with
neuroendocrine carcinoma of the small intestine remains unreported. In this report, we present the case of a 78-year-old man diagnosed with
neuroendocrine carcinoma of the small intestine and experienced symptoms such as subacute progressive
numbness of the extremities and impaired gait. These symptoms were diagnosed as
tumor-associated neurological syndrome. The patient had also undergone pyloric
gastrectomy for early-stage
gastric cancer several years prior to the appearance of the neurological symptoms. Therefore, we could not determine whether the
tumor-related neurologic syndrome was owing to
gastric cancer or
neuroendocrine carcinoma of the small intestine; however, one of these conditions was the cause of the neuropathy. The gait disturbance and
numbness relatively improved after surgery for the
neuroendocrine carcinoma of the small intestine, suggesting that the
neuroendocrine carcinoma of the small intestine likely caused the paraneoplastic neurological syndrome. Collectively, we present a unique report highlighting the putative relationship between small bowel
neuroendocrine carcinoma and
tumor-associated neurologic syndromes.