To investigate these issues the Danish National Birth Cohort (Better health for mother and child) was established. A large cohort of pregnant women with long-term follow-up of the offspring was the obvious choice because many of the exposures of interest cannot be reconstructed with sufficient validity back in time. The study needs to be large, and it is aimed to recruit 100,000 women early in pregnancy, and to continue follow-up for decades. The Nordic countries are better suited for this kind of research than most other countries because of their population-based registers on diseases, demography and social conditions, linkable at the individual level by means of the unique ID-number given to all citizens. Exposure information is mainly collected by computer-assisted telephone interviews with the women twice during pregnancy and when their children are six and 18 months old. Participants are also asked to fill in a self-administered food frequency questionnaire in mid-pregnancy. Furthermore, a biological bank has been set up with blood taken from the mother twice during pregnancy and blood from the umbilical cord taken shortly after birth. Data collection started in 1996 and the project covered all regions in Denmark in 1999. By August 2000. a total of 60,000 pregnant women had been recruited to the study. It is expected that a large number of gene-environmental hypotheses need to be based on case-control analyses within a cohort like this.

Contours of equal loudness were determined in the frequency range 2–63 Hz and the loudness range 20–100 phon. The loudness curves run almost parallel in the infrasonic frequency range and much closer than in the audio region. Infrasound only a few dB above the hearing threshold will therefore seem loud and possibly annoying. The subjects were 20 normal hearing students aged between 18 and 25, and the psychometric method was based on maximum-likelihood estimation of psychometric functions.

No abstract

Twenty‐nine high‐risk preterm born children, from a cohort with cerebral blood flow (CBF) measurements in the first 2 d of life, were examined prospectively at the age of 5.5—7 y neurologically, neuropsychologically and by magnetic resonance imaging (MRI). They were compared to 57 control children in terms of neurology and neuropsychology. Abnormal MRI was found in 19 children. Low oxygen delivery to the brain was found in 63% of them, in contrast to 12.5% in those with normal MRI, indicating neonatal hypoxia‐ischemia as an important factor. The MRI abnormalities were mainly periventricular lesions (n = 19), especially periventricular leucomalacia (PVL, n = 17). Three of the very preterm children had severe cerebellar atrophy in addition to relatively mild periventricular abnormalities. MRI showed specific morphological correlates for the major disabilities, e.g. spastic CP (involvement of motor tracts), mental retardation (bilateral extensive white matter reduction or cerebellar atrophy) and severe visual impairment (severe optic radiation involvement). A morphological correlate for minor disabilities, i.e. functional variations in motor performance or intelligence, was not found, with the exception that symptoms of attention deficit hyperactivity disorder were related to mild MRI abnormalities. This could mean that with respect to cognitive functions, mild or unilateral periventricular MRI lesions could be compensated. However, as among preterms without mental retardation (n = 19), IQ was generally and significantly lower than in the control group; other, more chronic pathogenetic factors, not detectable by MRI alone, may play a role. □Attention deficit hyperactivity disorder, cerebral blood flow, cerebral palsy, magnetic resonance imaging, oxygen delivery, periventricular leucomalacia, prematurity

Background: Whole-brain N-acetyl aspartate (NAA), a measure of neuronal function, can be assessed by multislice echo-planar spectroscopic imaging. Objective: To test the hypothesis that the global brain NAA/creatine (Cr) ratio is a better predictor of cognitive dysfunction in multiple sclerosis than conventional magnetic resonance imaging measures. Design: Survey. Setting: Research-oriented hospitals. Patients: Twenty patients, 16 women and 4 men (mean age, 36 years), with early relapsing-remitting multiple sclerosis (mean Expanded Disability Status Scale score, 2.5). Main Outcome Measures: Correlation between the global NAA/Cr ratio and a cognitive dysfunction factor comprising 16 measures from an extensive neuropsy-chological test battery that best distinguished patients with multiple sclerosis from healthy control subjects. Results: A significant partial correlation between the global NAA/Cr ratio and the cognitive dysfunction factor was found (partial r = 0.62, P = .01), and 9 cognitively impaired patients had significantly lower global NAA/Cr ratios than 11 unimpaired patients (P=.04). No significant correlations were found between the cognitive dysfunction factor and conventional magnetic resonance imaging measures (ie, brain parenchymal fraction and lesion volume). Conclusions: Multislice echo-planar spectroscopic imaging provides global metabolic measures that distinguish between cognitively impaired and unimpaired patients with multiple sclerosis and correlate with a global cognitive measure. Standardization of the technique is needed, and largerscale studies that include healthy controls are suggested.

The study included 16 adolescents with optimally controlled hyperphenylalaninaemia (McKusick 26160), of whom six did not require treatment according to conventional criteria. All except the two patients with lowest median serum phenylalanine level throughout childhood (most values at 200-300 mumol/L) had white matter abnormalities detectable with magnetic resonance imaging. The lesions were particularly prominent in the watershed regions between the posterior and middle cerebral arteries. In most patients with moderate or severe hyperphenylalaninaemia frontal white matter lesions were present as well. Normal proton magnetic resonance spectra indicated that the lesions were stable. Occipital EEG abnormalities were frequent, and deficient performance on a pattern-recognition test was a characteristic neuropsychological finding. Serum phenylalanine levels at about 300 mumol/L or below throughout childhood and early adolescence may be required to avoid lesions. The present study demonstrates the limitations of even an optimally controlled dietary regimen in hyperphenylalaninaemia.

Eighteen subjects (age range: 18-25) rated the annoyance of 18 sound stimuli on a graphic scale (four infrasonic frequencies at different intensity levels and four levels of 1000Hz octave-ftltered pink noise for reference). The exposure time for each stimulus was 15 minutes. The order of exposures was determined from a latin square and each subject was exposed to only one stimulus per day. Equal annoyance contours were constructed to connect points that produced the same annoyance rating. The equal annoyance curves demonstrate that the lower the frequency the greater must be the sound pressure to cause a given amount of annoyance. Compared with 1000 Hz the curves lie much closer together in the infrasonic range. The closeness of the curves in the infrasonic region implies that small changes in sound pressure may cause relatively large changes in annoyance. Based on the experimental results a weighting curve with a slope of 12 dB per octave is suggested for the assessment of annoyance and loudness in the infrasonic range. A curve with the same slope and an attenuation of 0 dB at 10 Hz is at present under consideration in the International Standardization Organization. For environmental purposes a maximum permitted level of 95 dB is proposed for use with this curve.

Our results suggest that even in the NABT MR detects changes likely to be associated with an underlying pathology and possibly contributes to the cognitive impairment in MS.