Total Brain Size Research Articles

Glucose Turnover Study in Children After Severe Brain Injury 178

In 1977, Bier et al described the linear relation of total body glucose flux and brain size in individuals (premature infants to adults) (r=0.97). We used Bier's method to evaluate the usefulness of measurement of glucose flux by 6,6 dideuteroglucose in the certification of brain injury. During a 15 month period, a prospective study was done with 13 patients admitted to PICU. They were divided in three groups: A-control, B-Glasgow Coma Scale less than 10, C-brain death. Prior to study, enteral feedings were discontinued for 8 hours and IVF's with D5W were tapered down in 4 hours. An intravenous bolus of 6-6 dideuteroglucose was followed by a continuous infusion of the isotope. Bedside glucose monitoring was done every 30 minutes, and blood samples were drawn at 0, 120, 150, 180, 210 and 240 minutes for glucose, insulin and 6-6 dideuteroglucose enrichment. Expected glucose production rate (GPR) as a function of body weight was compared with the patient's GPR and expressed as percent of the expected. A low GPR was considered below 60%, borderline GPR was 60-80% and normal GPR was above 80%. Group A (n=3) had a mean GPR of 83%, group B (n=5) of 74% and group C (n=2) of 69%. All patients with normal neurologic outcomes had normal GPR. Patients with a low GPR died or, if survived experienced no improvement in their neurological status. Four patients that died had normal or borderline GPR. Two patients with normal or borderline GPR were discharged with moderate to severe brain damage. We conclude that the predictive value of GPR for a bad outcome in this group of patients is 100%. A normal GPR was not predictive of a good outcome. We speculate that patients with normal GPR but poor neurologic status at discharge may have a better recovery potential.

A prospective follow-up study of brain morphology and cognition in first-episode schizophrenic patients: Preliminary findings

Brain morphological abnormalities have been reported in several independent investigations of chronic schizophrenic patients. The present study is a prospective 4-year follow-up of first-episode schizophrenic patients to determine whether some of these abnormalities may be a consequence of regional brain structural change over time after the onset of a first psychotic episode. Whole hemisphere, temporal lobes, superior temporal gyrus, hippocampus, caudate, corpus callosum, and lateral ventricles were measured in a series of MRI scans taken over a 4-year period in 20 patients and five controls. Total volume reduction was noted in both hemispheres to a greater degree in patients than controls. When adjusted for total brain size, left ventricular enlargement occurred in patients, but not controls, over time. These preliminary data suggest that subtle cortical atrophy may be occurring over time after the onset of illness.

Magnetic resonance imaging volumetric measurements of the superior temporal gyrus, hippocampus, parahippocampal gyrus, frontal and temporal lobes in late paraphrenia.

Quantified magnetic resonance measurements were made of superior temporal gyrus, parahippocampal gyrus, hippocampal, frontal and temporal lobe volumes and of the planar area of the thalamus and basal ganglia structures in 47 late paraphrenic patients and 33 healthy elderly controls. The late paraphrenics were divided into 31 schizophrenics and 16 patients with delusional disorder according to ICD-10 guidelines. Patients with delusional disorder tended to have smaller left temporal volumes compared with control subjects and patients with schizophrenia, but this difference failed to reach accepted levels of statistical significance after correction for the effects of multiple statistical comparisons, age and total brain size. Physiological right-left asymmetry, reported for temporal and frontal lobe volumes, was present in control, schizophrenic and delusional disorder subjects but delusional disorder patients had a significantly greater degree of temporal lobe asymmetry. The results add to the evidence for heterogeneity among late-onset psychoses and emphasize the subtle nature of any structural brain abnormalities in these patients.

Natural space-use patterns and hippocampal size in kangaroo rats.

The size of the hippocampus, a forebrain structure that processes spatial information, correlates with the need to relocate food caches by passerine birds and with sex-specific patterns of space use in microtine rodents. The influences on hippocampal anatomy of sexual selection within species, and natural selection between species, have not yet been studied in concert, however. Here we report that natural space-use patterns predict hippocampal size within and between two species of kangaroo rats (Dipodomys). Differences in foraging behavior suggest that Merriam's kangaroo rats (D. merriami) require better spatial abilities than bannertail kangaroo rats (D. spectabilis). Sex-specific differences in mating strategy suggest that males of both species require more spatial ability than females. As predicted, hippocampal size (relative to brain size) is larger in Merriam's than in bannertail kangaroo rats, and males have larger hippocampi than females in both species. Males of a third species (D. ordii) also have smaller hippocampi than Merriam's kangaroo rat males, despite being similar to Merriam's in brain and body size. These results suggest that both natural and sexual selection affect the relative size and perhaps function of mammalian hippocampi. They also reassert that measures of functional subunits of the brain reveal more about brain evolution than measures of total brain size.

Neuroanatomical correlates of age-sensitive and age-invariant cognitive abilities: An in vivo MRI investigation

The relationship between brain asymmetry and age-related differences in cognitive abilities was examined in a sample of 29 healthy volunteers (18 to 78 years old). The volumes and areas of cerebral hemispheres as well as several cortical and subcortical regions were estimated from magnetic resonance imaging (MRI) scans. Fluid and crystallized intelligence were assessed by tests of nonverbal reasoning and vocabulary. The magnitude of leftward hemispheric volume asymmetry significantly and uniquely contributed to explaining the variance in both cognitive measures. None of the indices of regional hemispheric asymmetry showed a similar pattern of associations with intelligence. Although total brain size, and the size of dorsolateral prefrontal cortex positively correlated with fluid intelligence, they also correlated with age and head size, and did not add significantly to the fluid intelligence variance explained by age alone.

Evidence of Decrease in Brain Size in Ranch Mink, <i>Mustela vison </i>f. dom., during Subadult Postnatal Ontogenesis

Total brain size and the volume of several brain parts were compared in male and female ranch mink of varying age and body size in an attempt to quantify postnatal maturation and growth processes in this altricial species. Volumes of fresh whole brains and of different brain parts were calculated from prepared histological sections from juvenile (2- to 3-month-old), subadult (5-month-old), and adult (older than 7 months) individuals. Allometrical calculations were performed on the basis of body weight. Changes in size of different parts of the brain obtained to different degrees were found to be dependent on age but independent of body size. From the juvenile stage to the subadult stage, total brain size remains unchanged, although most major brain parts increase in size, while the grey matter of the isocortex decreases. During subsequent development from subadult to adult, total brain size evidently decreases. Within the brain all major structures also decrease in size, except for the medulla oblongata and the mesencephalon, which remains relatively stable in size. The grey matter of the isocortex shows the greatest decrease, followed by the allocortex and corpus striatum, the cerebellum, the white matter of the isocortex, and the diencephalon. Thus, an unusual but evident 'overshoot' in size of the total brain and certain parts apparently occurs in this species before adulthood is reached. This phenomenon is discussed in connection with size changes concomitant with domestication as well as with cageing of individuals and with postnatal and seasonal size changes known from some soricid species as the so-called Dehnel phenomenon.

Normal pituitary gland: changes in shape, size, and signal intensity during the 1st year of life at MR imaging.

Magnetic resonance images of the pituitary glands in 48 endocrinologically normal neonates and infants were analyzed to determine the changes in pituitary gland size, shape, and signal intensity that occur during the 1st year of life. A progressive increase in the length--but not height--of the gland was seen throughout the 1st year. When corrections for total brain size were made, the pituitary gland was found to diminish in relative cross-sectional area throughout infancy. Upward convexity of the gland was seen in 63% of neonates less than 1 month of age, but in only 4% of infants older than 2 months. Hyperintensity of the adenohypophysis relative to the brain stem was visualized on T1-weighted images in 18 of the 24 (75%) neonates and infants less than 2 months old; this appearance was never seen in older infants. An area of high signal intensity was visualized in the posterior pituitary in 32 of 48 cases (67%), and its visualization was unrelated to age. The neonatal and young infant pituitary gland is thus significantly rounder, brighter, and relatively larger during the first 2 months of life than in later infancy.