Involvement of the capsular genu in reward-related feeding

Abstract

Dear Sirs, Food intake is regulated by homeostatic and reward-related pathways. The hypothalamus and brainstem integrate homeostatic signals with reward-related pathways, such as the dopaminergic neurons of the ventral tegmental area, nucleus accumbens, insular cortex, anterior cingulate cortex, and orbitofrontal cortex [1]. Eating disorders following brain lesions of the frontal and temporal lobe, hypothalamus, thalamus, and brainstem have all been described [2–4]. A 58-year-old right-handed woman suddenly presented with abnormal eating behavior and excessive daytime sleepiness in August 2009. The patient was seen consuming a large amount of salt-boiled, green edamame-type soybeans by a family member, and she slept throughout the day, except for when she was eating, on the day before her admission. The patient had no history of eating disorder. Neurological examination was unremarkable except for memory disturbance. She scored 26 points on the MiniMental State Examination (MMSE) scale (the impaired items being related to orientation and recall). No frontal release signs were observed. Brain magnetic resonance imaging (MRI) showed an acute ischemic lesion in the right capsular genu (Fig. 1a), with deep white matter lesions. Sixteen days after onset of symptoms, the patient was discharged with mild residual cognitive impairment and daytime sleepiness. After discharge, the patient could not resist the urge to eat and consumed three packs of edamame per day, resulting in weight gain of 5 kg over 3 months. The feeling of hunger was not necessary for this eating behavior to occur. The patient admitted that, before the onset of stroke, she had wanted to eat edamame whenever she saw her husband eating them while drinking beer but that she had previously restrained herself from doing so. She did not display increased eating behavior with other foods. Her appetite and eating behavior returned to normal by November 2009. In August 2010, she returned to our outpatient clinic with a 2-month history of the previously observed symptoms of daytime sleepiness and increased consumption of edamame. Brain MRI showed bilateral capsular genu infarcts (Fig. 1b). Brain single-photon emission computed tomography (SPECT) showed hypoperfusion in the bilateral frontal lobes (Fig. 1c, d). She scored 23 points on the MMSE scale (the impaired items being related to orientation, attention, calculation, and recall). We report a patient who developed right and left capsular genu infarcts on two separate occasions; both episodes were associated with identical clinical symptoms of increased reward-related feeding and daytime sleepiness. The patient displayed an irrational desire to consume edamame. Edamame is a nutritious green vegetable, also known as fresh green soybean, which is harvested at the peak of ripening just before it reaches a hardening stage. The stroke of each side of the capsular genu in the same patient on different occasions, which induced reproducible abnormal eating behavior related only to palatable food in the absence of frontal release signs, suggests the involvement of reward-related food pathways. This behavior is in contrast with binge eating, which is observed in patients with thalamic infarcts [2, 4]. However, because our patient K. Suzuki (&) T. Sada H. Takekawa K. Hirata Department of Neurology, Dokkyo Medical University, 880 Kitakobayashi, Mibu, Shimotsuga, Tochigi 321-0293, Japan e-mail: keisuke@dokkyomed.ac.jp