Cognitive impairment associated with carcinoid syndrome

To evaluate the cognitive performance of patients with carcinoid syndrome (CS) compared with population norms and cancer patients with non-neuroendocrine (non-NET) liver metastases.

The release of serotonin into the systemic circulation from metastatic small bowel neuroendocrine tumors (SB NET) causes CS. Many patients with CS followed in a multidisciplinary NET clinic seemed to exhibit a unique cognitive impairment. Because serotonin is known to influence a range of cognitive function, the question arouse as to whether cognitive impairment is another manifestation of CS.

Patients were recruited from the multidisciplinary NET and the hepatobilary cancer clinics at the cancer center. The CS group consisted of patients with proven SB NETs metastatic to liver; the cancer comparison group consisted of patients with liver metastases from non-NET cancer. All completed a self-reported cognitive questionnaire and a battery of 6 standardized neurocognitive tests. Both groups were compared to age/sex/educational-matched norms.

Thirty-six patients with CS and 20 with non-NET metastases were enrolled. Patients with CS reported greater cognitive dysfunction in all cognitive domains than both norms and the comparison cancer group. On cognitive testing, patients with CS demonstrated weakness in initiation, processing speed, visual memory, cognitive efficiency, and delayed verbal recall compared with norms. Although the patients with non-NET cancer also demonstrated some cognitive dysfunction compared with norms, the patients with CS did significantly worse on delayed recall (P = 0.03) and marginally slower on speeded mental flexibility (P = 0.097) compared with patients with non-NET cancer.

This study confirmed our clinical observation that patients with CS suffer from cognitive impairment that is different from the non-NET cancer group and population norms.