The pathogenesis of bipolar disorder (BD) is to date not entirely clear. Classical genetic research showed that there is a contribution of genetic factors in BD, with high heritability. Twin studies, thanks to the fact that confounding factors as genetic background or family environment are shared, allow etiological inferences. In this work, we selected twin studies, which focus on the relationship between BD, genetic factors and brain structure, evaluated with magnetic resonance imaging. All the studies found differences in brain structure between BD patients and their co-twins, and also in respect to healthy controls. Genetic effects are predominant in white matter, except corpus callosum, while gray matter resulted more influenced by environment, or by the disease itself. All studies found no interactions between BD and shared environment between twins. Twin studies have been demonstrated to be useful in exploring BD pathogenesis and could be extremely effective at discriminating the neural mechanisms underlying BD.

Two men, 56 and 33 years old, (case 1 and case 2) were examined neuropsychologically after successful resuscitation from circulatory arrest following extreme accidental hypothermia and near drowning. After submersion in ice water for at least 20 minutes they received CPR for 45 to 60 minutes. Body-core temperature at start of CPB was 24°C and 22°C, respectively. A neuropsychological examination was performed within two months after the accident and 1 year later. An additional follow-up interview was made 3 years after the accidents. Both had severe problems with memory, visuospatial performance, executive function, and verbal fluency. The follow-up demonstrated improvement in the visuospatial test in both and in the verbal learning, recall, and logical reasoning tests in case 2. Both still had problems with executive function, and case 2 also in verbal fluency. Case 1 also had problems with flexibility, planning and abstract ability. Despite the protective effects of hypothermia and gradual improvement of symptoms over time, some of the deficits were permanent. A thorough neuropsychological examination of patients suffered from anoxia is advisable, because gross neurological examination and MRI scans may not always reveal underlying brain dysfunction. (JINS, 2008, 14, 660–666.)

Despite evidence for executive dysfunction in school-aged preterm children, less is known about the early development of these difficulties or their underlying neuropathology. This study used prospective longitudinal data from a regional cohort of 88 very preterm and 98 full-term comparison children to examine the executive functioning (EF) of preschool children born very preterm. The relationship between the severity of neonatal cerebral white matter (WM) abnormalities on magnetic resonance imaging (MRI) at term equivalent and children's EF at ages two and four years (corrected age) was examined. At age four, very preterm children with WM abnormalities performed less well than full-term children on the Detour Reaching Box, a measure of behavioral inhibition and cognitive flexibility, even after controlling for child IQ, SES, and medical background. Examination of patterns of EF performance between the ages of 2 and 4 years showed that the performance of all groups improved with age. However, very preterm children with mild and moderate-severe WM abnormalities were characterized by higher rates of consistent performance impairments. These findings support the presence of early and persistent executive difficulties in preschool children born very preterm, and highlight the importance of white matter pathology in the development of executive impairments. (JINS, 2008, 14, 90–101.)