EVEN MINOR RISK OF OXYGEN DEPRIVATION AT OR IMMEDIATELY AFTER BIRTH MAY PLACE PREMATURE BABIES AT GREATER RISK FOR COGNITIVE AND LANGUAGE PROBLEMS, PROPORTIONATE TO THE DEGREE OF "HYPOXIA"

 

 

WASHINGTON - Birth is a time of peril for the human brain, especially in pre-term infants. For vulnerable "preemies," biochemical signs of reduced blood oxygen levels (hypoxia) soon after birth are associated with lower IQs and language skills. In 2001, premature babies were 12 percent of U.S. births - the highest level in 20 years, due in part to more multiple pregnancies, induced labor, and older mothers. The January issue of Neuropsychology, published by the American Psychological Association (APA) reports on links among pre-term birth, risk for birth hypoxia and cognitive problems, and reveals how the risk threshold for brain damage in preterm babies could be lower than thought.

Psychologists compared the intellectual and language development of five- and six- year olds, all of whom had been born prematurely. Half the group were, during or immediately following birth, at slight to moderate risk for hypoxia. The other half had no such risk, although they resembled the risk group on other early risk factors and on socio-demographic characteristics. Despite the relatively small difference between the groups in the degree of risk, the authors report that the two groups "diverged significantly" in their development.

The relationship between mild to moderate birth hypoxia and later cognitive abilities contradicts established wisdom that regards severe oxygen deprivation as the threshold for brain damage in an "all or nothing" manner. The findings add to other recent evidence of a continuum of brain injury due to asphyxia around birth.

The researchers, at Wayne State University, The University of Memphis, and Baptist Memorial Hospital in Memphis, studied 52 children. All had been born at or before 36 weeks (normal term is about 40 weeks). Twenty six of the children were at slight to moderate risk of perinatal hypoxia, as measured by higher blood acidity within two hours of birth (lower than normal arterial blood pH). The other 26 children in the comparison group were at lower perinatal risk.

Co-authors Tracy Hopkins-Golightly, Ph.D., Sarah Raz, Ph.D., and Craig J. Sander, M.D. tested all 52 children at an average age of six on intelligence and language (receptive and expressive) skills.

There was a significant relationship between blood pH soon after birth and later cognitive and language skills. For example, the pre-term group, with mild to moderate acidosis, scored about 10 to 11 points lower on verbal and visuospatial tests than the low-risk pre-term group - a large discrepancy. Such data, say the authors, reveal that even a minor risk for hypoxia around birth may have a "discernible influence on the course of cognitive development."

Says Raz, now at Wayne State University in Detroit, "most neonatologists would probably not expect to find a statistically significant relationship between degree of acidosis measured soon after birth and performance on cognitive tests in preschool and early school-age children, when acidosis is only mild to moderate, at worst".

Although it is well-known that premature babies tend to have more cognitive problems than full-term infants, scientists want to tease out the specific complications -- from a host of many - that cause the most trouble. A good way to do that is to compare two groups of preterm infants, who share the risks of pregnancy, delivery and the vulnerable postnatal period, but who differ in terms of one single, special risk factor (such as birth hypoxia).

Structural or functional imaging, such as MRI, may shed light on which brain areas are the most vulnerable to damage by hypoxia in the preterm infant. For now the authors speculate that, in babies born prematurely, even minor risk may be associated with damage to the periventricular white matter, deep inside the brain.

By linking birth complications to specific cognitive problems occurring later, scientists hope to understand the brain's vulnerability to insult during early human development. Furthermore, knowledge of how early risk factors affect cognitive abilities may help doctors to evaluate the effectiveness of medical interventions that support preterm infants during and after birth.

Article: "Influence of Slight to Moderate Risk for Birth Hypoxia on Acquisition of Cognitive and Language Function in the Preterm Infant: A Cross-Sectional Comparison With Pre-Term Birth Controls," Tracy Hopkins-Golightly, Ph.D., University of Memphis; Sarah Raz, Ph.D. University of Memphis and Wayne State University; and Craig J. Sander, M.D., Baptist Memorial Hospital; Neuropsychology, Vol. 17, No. 1.

A Look Into the Teenage Brain

Scientists used to think that the teenage brain more closely resembled the adult brain than a child's brain. Recent studies have indicated that isn't necessarily the case. The August 9th, 1999, issue of "US News and World Report" reported on some of the most recent findings.

Most teens don't wear trench coats and shoot fellow students, but adults have often been amazed at how teens can seem to be happy-go-lucky, well-adjusted, seemingly-normal people one minute and ranting, raving lunatics who are impossible to understand the next.

The single most frustrating thing to parents of teens is the fact that they can run so hot and cold. One minute they love you and the next they hate you. The reason for this seems hidden deep inside the teenage brain.

Since the inception of the M.R.I. (magnetic resonance imaging) scientists have been able to study the human brain in ways never thought possible before. Adults and teens wired for study purposes are given certain stimuli and certain regions of the brain light up with activity. What puzzled researchers at first was that adult brains light up in both the prefrontal cortex and the limbic regions almost simultaneously. Teen brains only light the limbic region and the prefrontal cortex region stays dark.

The problem with the fact that teen prefrontal cortex regions of the brain show practically no activity is that the prefrontal cortex is like the CEO of the brain. The limbic region is the seat of the emotions. It is no wonder teens are so ruled by emotions and seem to be so illogical. The "US News" article states "the prefrontal cortex is the seat of civilization." The part of the brain that will later balance the emotions with reason and common sense is sadly asleep at the wheel until long after puberty.

The limbic region, found deep within the brain, is the source of raw emotions such as anger. Unfortunately, the limbic region goes into hyperdevelopment mode during the teen years. The raw emotions are tempered in adult brains by signals from the prefrontal cortex. According to Karl Pribriam, director of the Center for Brain Research and Informational Sciences at Radford University in Virginia, "the prefrontal cortex is in charge of `executive functions.' "These include the brain's ability to handle ambiguous information and make decisions, to coordinate signals in different regions of the brain, and to tamp down or prolong emotions generated in the limbic system."

"In an adult, for instance, an overheard insult might arouse a murderous rage, until the prefrontal cortex figures out that the comment was meant for somebody else and tells the limbic system to pipe down."

Teens shown pictures of faces with certain strong emotions were almost never able to tell what emotion was being expressed. Adults shown the same pictures almost always knew what emotion was being shown. This reveals yet another piece of the puzzle in trying to understand teenagers.

The gist of the "US News" seemed to be that teenagers are much like a computer. You can pump good information into them, but if the hardware is incapable of processing it therein lies the problem. The hardware in the teen brain is pretty much incapable of maturely processing information until the early twenties.

"The teenage tendency to leap before looking is compounded by the fact that adolescence is a time for seeking out new experiences, including some that are dangerous. `I think all people do stupid things sometimes. It just seems like teenagers do it more often,' says Rachel Fisher, an 18-year-old senior from Lakewood, Colo. That's an understatement. Driving without a seatbelt, getting tattooed, smoking cigarettes, shoplifting-the list of foolish things kids do is longer than most parents really want to know."

The good news for parents seems to be "that the vast majority of kids will make it through adolescence with few permanent scars, except for the occasional hole through a belly button. New research shows that most children emerge from adolescence physically and emotionally intact-although their parents will probably never be the same."

It probably won't help parents to tell their teenagers that we know their brains are a work in progress. It might help parents to realize that teen brains are incapable of processing information the same way adult brains do. So next time your teen looks at you in that certain way only a teenager can, just look back at them and smile, realizing full well that his/her brain is only half there for a few more years.

HYPERBARIC OXYGEN IMPROVES PERIPHERAL NERVE REGENERATION

Several studies have documented the effectiveness of hyperbaric oxygen in models of acute and delayed crush injury. Intermittent exposure to hyperbaric hyperoxia serves to interrupt the injury cycle of edema, ischemia and tissue necrosis(1), as well as hemorrhagic hypotension(2), which in turn leads to former edema and ischemia. Tissue ischemia is countered by the ability of hyperbaric doses of oxygen to elevate tissue oxygen tensions(3). Furthermore, edema is reduced, secondary to hyperoxia-induced arteriolar vasoconstriction(4), leading to improved tissue viability, thereby reducing necrosis(1). Hyperbaric oxygen has also been studied in models of peripheral nerve injury(5).

Researchers from the US Air Force School Aerospace Medicine and Louisiana State University recently sought to determine what, if any, morphologic changes are associated with hyperbaric oxygen treated peripheral nerve injury(6). Their model involved a crushed sciatic nerve in the rabbit.

Exposure to hyperbaric oxygen across the range of current clinical dose schedules was compared to untreated, and pressure (hyperbaric air) controls. The extent of nerve regeneration was documented via morphologic analysis of electron micrographs, by a pathologist blinded as to group.

All of the animals exposed to hyperbaric doses of oxygen were reported to demonstrate advanced stages of a healed nerve, in contrast to both control groups.

As this research was limited to a determination of regeneration of morphology, the exact effects of hyperbaric oxygen were not known. The authors speculate, however, that there may be several suggesting increased myelination, decreased edema, reduced internal collagen and improvements in neurofilamentous material density.

They conclude that this study provides additional evidence of a link between tissue oxygen levels and the health of peripheral nerves.

... all animals exposed to hyperbaric oxygen "demonstrated characteristics expected of in the advanced stages of a healed nerve"

References:

  • Strauss MB et al.: Delayed use of hyperbaric oxygen for treatment of a model anterior compartment syndrome. Journal of Orthopedic Research 1986; 4:108-111.
  • Skyhar MJ et al.: Hyperbaric oxygen reduces edema and necrosis of skeletal muscle in compartment syndromes associated with hemorrhagic hypotension. Journal of Bone and Joint Surgery 1986;68A:1218-1224
  • Nylander G: Tissue ischemia and hyperbaric oxygen treatment. Scand 1986; suppl. 533.
  • Nylander G et al.: Reduction of postischemic edema with hyperbaric oxygen. Plastic and Reconstructive Surgery 1985;76:595-603
  • Zamboni WA et al.: Functional evaluation of peripheral-nerve repair and the effect of hyperbaric oxygen. Journal of Reconstructive Microsurgery 1995; 11:27-29.
  • Bradshaw PO, et al.: Effect of hyperbaric oxygenation on peripheral nerve regeneration in adult male rabbits. Undersea and Hyperbaric Medicine 1996; 23(2): 107-113.
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