title: Insulinoma Masquerading as Rapid Eye Movement Sleep Behavior Disorder: Case Series and Literature Review.
abstract: Insulinoma is a rare endocrine tumor that can cause a wide variety of symptoms, including abnormal nocturnal behavior. We report on 3 patients with insulinoma who presented with abnormal nocturnal behavior and injury during sleep, which simulated rapid eye movement (REM) sleep behavior disorder (RBD). In case 1, the fasting glucose level was 15  mg/dL, and insulin levels were elevated (15  μU/mL). In case 3, when the patient was transferred to the hospital because of a disturbance of consciousness, hypoglycemia (29  mg/dL) was detected. In contrast, in case 2, fasting glucose sampling did not indicate hypoglycemia, but continuous glucose monitoring revealed nocturnal hypoglycemia. The time from initial symptoms to a diagnosis of insulinoma ranged from 7 months to 2 years. All 3 patients had previously received anticonvulsant drugs for suspected epilepsy, but the medications were ineffective. Polysomnography showed no evidence of REM sleep without atonia in any of the 3 patients. No patient remembered any events that occurred during sleep. When a patient manifests abnormal behavior during the night and early morning, glucose monitoring should be performed, especially during the night and early morning. Clinicians should be aware that although insulinomas are rare, they can mimic parasomnias, such as RBD.
authors.affiliation: From the Department of Neurology (KS, AK, KH), Dokkyo Medical University, Tochigi, Japan; School of Nursing (MM), Dokkyo Medical University, Tochigi, Japan; Department of Neurology (TM), Dokkyo Medical University, Koshigaya Hospital, Saitama, Japan; Department of Neuropsychiatry (TK, MS, TS), Akita University School of Medicine, Akita, Japan; and International Institute for Integrative Sleep Medicine (WPI-IIIS) (TK, TS), University of Tsukuba, Tsukuba, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Suzuki
authors.forename: Akiko
authors.initials: A
authors.lastname: Kawasaki
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyamoto
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanbayashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Sato
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Shimizu
authors.forename: Koichi
authors.initials: K
authors.lastname: Hirata
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007340:Insulinoma / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D020187:REM Sleep Behavior Disorder / Q000175:diagnosis*