New and Noteworthy Information—May 2014
The International League Against Epilepsy has altered its practical definition of epilepsy per the recommendation of a task force, according to an article published online ahead of print April 14 in Epilepsia. Recognizing the limitations of the practical definition of epilepsy as two unprovoked seizures more than 24 hours apart, the task force proposed that epilepsy be considered to be a disease of the brain defined by any of the following conditions: (1) At least two unprovoked (or reflex) seizures occurring more than 24 h apart; (2) one unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk (ie, at least 60%) after two unprovoked seizures, occurring over the next 10 years; (3) diagnosis of an epilepsy syndrome.
Older people who have apathy but not depression may have smaller brain volumes than those without apathy, according to data published online ahead of print April 16 in Neurology. Investigators performed cross-sectional analyses of data from 4,354 persons without dementia (average age, 76) participating in a population-based study. Apathy symptoms were assessed with the Geriatric Depression Scale. Brain volumes and total white matter lesion (WML) volume were estimated on 1.5-T MRI using an automated segmentation program. Regional WML load was calculated using a semiquantitative scale. Compared with individuals with fewer than two apathy symptoms, participants with two or more apathy symptoms had significantly smaller gray matter volumes, smaller white matter volumes, and smaller thalamus volumes. The latter individuals also were more likely to have WMLs in the frontal lobe.
The APOE4 gene variant confers a substantially greater risk for Alzheimer’s disease to women than it does to men, researchers reported online ahead of print April 14 in Annals of Neurology. The group performed Cox proportional hazards analysis to compute hazard ratios (HRs) for an APOE-by-sex interaction on conversion in 5,496 healthy individuals and 2,588 patients with mild cognitive impairment (MCI). The investigators also tested the interaction in CSF biomarker levels of 980 subjects from the Alzheimer’s Disease Neuroimaging Initiative. Among controls, male and female carriers were more likely to convert to MCI or Alzheimer’s disease, but the effect was stronger in women (HR, 1.81 for women; HR, 1.27 for men). The interaction remained significant in a predefined subanalysis that was restricted to APOE3/3 and APOE3/4 genotypes.
The size and shape of the nucleus accumbens and the amygdala may differ in young adults who smoke marijuana at least once a week, according to a study published April 16 in the Journal of Neuroscience. Investigators collected high-resolution MRI scans on young adults who used recreational marijuana and on controls. The researchers conducted three independent analyses of morphometry in gray matter density, volume (total brain and regional volumes), and surface morphometry. The study authors found greater gray matter density in marijuana users than in control participants in the left nucleus accumbens extending to the subcallosal cortex, hypothalamus, sublenticular extended amygdala, and left amygdala, even after controlling for age, sex, alcohol use, and cigarette smoking. Trend-level effects were observed for a volume increase in the left nucleus accumbens only.
Neuronal death in Parkinson’s disease may occur when the immune system mistakes neurons for foreign invaders and kills them, according to a study published April 16 in Nature Communications. An examination of postmortem brain tissue revealed major histocompatibility complex class I (MHC-1) proteins in catecholaminergic substantia nigra and locus coeruleus neurons. When researchers conducted in vitro experiments with mouse neurons and human neurons created from embryonic stem cells, they found that under certain circumstances, including conditions that occur in Parkinson’s disease, the neurons use MHC-1 to display antigens. Among the different types of neurons tested, the two types affected in Parkinson’s disease were far more responsive than other neurons to signals that triggered antigen display. The researchers also confirmed that T cells recognized and attacked neurons displaying specific antigens.
People who have had a stroke who consistently control their blood pressure may reduce the likelihood of a second stroke by more than half, according to research published online ahead of print March 27 in Stroke. In a post hoc analysis, 3,680 individuals with recent stroke who were followed up for two years were grouped according to the proportion of visits during which their blood pressure was controlled (ie, <140/90 mm Hg). Consistency of blood pressure control affected outcomes in individuals with baseline systolic blood pressure greater than 132 mm Hg. Among individuals with baseline systolic blood pressure higher than 153 mm Hg, risks of stroke, myocardial infarction, or vascular death were lower in those with blood pressure controlled during 75% or more visits, versus less than 25% of visits.
