Mary Catherine Lessig

Brain activation by disgust-inducing pictures in obsessive-compulsive disorder

BACKGROUND There is growing interest in the role of disgust in the pathogenesis of obsessive-compulsive disorder (OCD). METHODS Eight OCD subjects with contamination preoccupations and eight gender- and age-matched healthy volunteers viewed pictures from the International Affective Picture System during functional magnetic resonance imaging scans. RESULTS A different distribution of brain activations was found during disgust-inducing visual stimulation in several areas, most notably the insula, compared with neutral stimulation in both OCD subjects and healthy volunteers. Furthermore, whereas activation during the threat-inducing task in OCD subjects showed a pattern similar to that in healthy volunteers, the pattern of activation during the disgust-inducing task was significantly different, including greater increases in the right insula, parahippocampal region, and inferior frontal sites. CONCLUSIONS This pilot study supports the relevance of disgust in the neurocircuitry of OCD with contamination-preoccupation symptoms; future studies looking at non-OCD individuals with high disgust ratings, non-contamination-preoccupied OCD individuals, and individuals with other anxiety disorders are needed.

Satiety dysfunction in Prader-Willi syndrome demonstrated by fMRI.

The neurobiology relating to the insatiable appetite observed in Prader-Willi syndrome (PWS) has not been fully characterised. Two functional magnetic resonance imaging (fMRI) scans were performed on each of three adults with PWS. The scans were carried out pre- and post-treatment with the antiepileptic topiramate, which had little effect on body weight and appetite in these subjects. Subjects fasted overnight and drank a 75 g dextrose solution prior to fMRI scans for measurement of brain activation levels during/after glucose ingestion. Following glucose administration, there was a significant delay in activation at the hypothalamus and other brain regions associated with satiety compared with previous data on obese volunteers. These regions include the insula, ventromedial prefrontal cortex, and nucleus accumbens. Individuals with PWS showed a mean latency of 24 min while in a previous study obese volunteers had shown a latency of 15 min and lean volunteers a latency of 10 min in the hypothalamus. Our results provide evidence towards a satiety dysfunction in the central nervous system of PWS patients.

Effects of Topiramate in Adults With Prader-Willi Syndrome

Prader-Willi syndrome is a multisystem neurogenetic obesity disorder with behavioral manifestations, including hyperphagia, compulsive behavior, self-injury, and mild to moderate mental retardation. In an 8-week open-label study, we evaluated adjunctive therapy with the anticonvulsant topiramate in 8 adults with Prader-Willi syndrome. Appetite was measured by a 1-hour access to food four times throughout the study and quantified with a visual analogue scale. Topiramate did not significantly change calories consumed, Body Mass Index, or increase self-reported appetite. In addition, there were no significant changes in compulsions. Surprisingly, topiramate treatment resulted in a clinically significant improvement in the self-injury (i.e., skin-picking) that is characteristic of this syndrome. Potential benefits of topiramate for self-injury should be evaluated further in controlled trials.

Topiramate attenuates self-injurious behaviour in Prader-Willi Syndrome.

Self-injurious behaviour (SIB), most notably skin picking, has been described by various terms in the literature ranging from neurotic/psychogenic excoriations to compulsive/pathological skin picking. Prader-Willi Syndrome (PWS) is a neurogenetic multisystem disorder characterized by infantile hypotonia, mental retardation, short stature, hypogonadism, dysmorphic features, and hyperphagia with a high risk of obesity. Psychiatric manifestations include SIBs in the form of skin picking, nail biting and rectal gouging. Topiramate is a novel anti-epileptic medication without significant liability of weight gain. There are no published reports of topiramate being utilized in PWS or SIB. We report attenuation of SIB with resultant lesion healing in three PWS adults treated with topiramate in an 8-wk open-label trial. Although our findings should be treated with caution, they suggest that double-blind or cross-over studies with topiramate are warranted to establish the possible role of topiramate in attenuating SIB in PWS and other disorders that involve SIB.