Masanori Namba

Developmental changes of optical properties in neonates determined by near-infrared time-resolved spectroscopy.

Near-infrared spectroscopy has been used for measurement of changes in cerebral Hb concentrations in infants to study cerebral oxygenation and hemodynamics. In this study, measurements by time-resolved spectroscopy (TRS) were performed in 22 neonates to estimate the values of light absorption coefficient and reduced scattering coefficient (μs), cerebral Hb oxygen saturation (Sco2), cerebral blood volume (CBV), and differential pathlength factor (DPF), and the relationships between postconceptional age and μs, Sco2, CBV, and DPF were investigated. A portable three-wavelength TRS system with a probe attached to the head of the neonate was used. The mean μs values at 761, 795, and 835 nm in neonates were estimated to be (mean ± SD) 6.46 ± 1.21, 5.90 ± 1.15 and 6.40 ± 1.16/cm, respectively. There was a significant positive relationship between postconceptional age and μs at those three wavelengths. The mean Sco2 value was calculated to be 70.0 ± 4.6%, and postconceptional age and Sco2 showed a negative linear relationship. The mean value of CBV was 2.31 ± 0.56 mL/100 g. There was a significant positive relationship between postconceptional age and CBV. The mean DPF values at 761, 795, and 835 nm were estimated to be 4.58 ± 0.41, 4.64 ± 0.46, and 4.31 ± 0.42, respectively. There was no relationship between postconceptional age and DPF at those three wavelengths. The results demonstrated that our near-infrared TRS method can be used to monitor μs, Sco2, CBV, and DPF in the neonatal brain at the bedside in an intensive care unit.

Noninvasive optical imaging in the visual cortex in young infants.

During the developmental stage, the brain undergoes anatomic, functional, and metabolic changes necessary to support the complex adaptive behavior of a mature individual. Estimation of developmental changes occurring in different regions of the brain would provide a means of relating various behavioral phenomena to maturation‐specific brain structures, thereby providing useful information on structure‐function relationships in both normal and disease states. We used multichannel near‐infrared spectroscopy (MNIRS), a new noninvasive imaging technique for revealing the course of neural activity in selected brain regions, to monitor the activities of the visual cortex as mirrored by hemodynamic responses in infants subjected to photostimulation during natural sleep. In the infants, oxyhemoglobin and total hemoglobin decreased and deoxyhemoglobin increased in the visual cortex with photostimulation. This pattern of responses was different from the response pattern in adults reported previously. The different patterns of responses to photostimulation in the visual cortices of infants and adults might reflect developmental and behavioral differences. It may reflect a different functional organization of the visual cortex in infants or ongoing retinal development. Our results demonstrated that regional hemodynamic change could be detected in a small area around the visual cortex. MNIRS offers considerable potential for research and noninvasive clinical applications. Hum. Brain Mapping 22:124–134, 2004.

Relationship between Cerebral Interstitial Levels of Amino Acids and Phosphorylation Potential during Secondary Energy Failure in Hypoxic-Ischemic Newborn Piglets

The aim of this study was to determine the validity of the hypothesis that excitatory amino acids are related to phosphorylation potential during primary and secondary cerebral energy failure observed in asphyxiated infants. We report here the results of experiments using newborn piglets subjected to severe transient cerebral hypoxia-ischemia followed by resuscitation. We examined cerebral energy metabolism by phosphorus nuclear magnetic resonance spectroscopy and changes in levels of amino acid neurotransmitters in the cortex by microdialysis before, during, and up to 24 h after the hypoxic-ischemic insult. The concentrations of aspartate, glutamate, taurine, and γ-aminobutyric acid were significantly elevated during the hypoxic-ischemic insult compared with prebaseline values. Shortly after resuscitation, glutamate, taurine, and γ-aminobutyric acid concentrations decreased but then began to increase again. These secondary elevations were greater than the primary elevations. A negative linear correlation was found between primary interstitial levels of glutamate and taurine and minimum values of phosphocreatine/inorganic phosphate during the secondary energy failure. The cerebral energy state depended on the time course of changes in excitatory amino acids, suggesting that amino acids play distinct roles during the early and delayed phases of injury.

A 10-year-old boy with Marfan syndrome exhibiting cerebrovascular abnormalities

A young male with Marfan syndrome, diagnosed at the age of 10 years, presented with conspicuous elongation and tortuosity of the internal carotid, middle cerebral, vertebral and basilar arteries on cranial magnetic resonance and computed tomography angiography. There is a little mention of cerebral blood vessel examinations in the guidelines of the American Academy of Pediatrics for Marfan syndrome. Guidelines may be provided for the evaluation of cerebrovascular system for the patients with Marfan syndrome who have family history of Marfan syndrome as well as a family history of death from subarachnoid hemorrhage.

Estimation of circulating blood volume in infants using the pulse dye densitometry method

Background:  Estimation of hemodynamics is important for critically ill infants. Pulse dye densitometry (PDD) using indocyanine green (ICG), which enables measurements of circulating blood volume at the bedside, has recently been developed for adults.

Extrauterine environment affects the cortical responses to verbal stimulation in preterm infants.

Using optical topography, changes in the cerebral oxygenation were compared in the parieto-temporal lobe of preterm and term infants of equal postconceptional age in response to verbal stimulation. Eight preterm infants of gestational age 23-34 weeks were studied at postconceptional term age (38-46 weeks). Ten term infants were studied at 2-11 days after birth. Twenty-four-channel near-infrared optical topography (NIOT) was used to measure changes in concentration of oxyhemoglobin ([oxyHb]), deoxyhemoglobin ([deoxyHb]) and total hemoglobin ([totalHb]) in the bilateral temporal cortices. Verbal stimulation was provided by a recording of a Japanese fairy tale. The latency in response to verbal stimulation was significantly shorter in the preterm infants than in the term infants. This time is thought to reflect brain development, particularly the development of the neuro-vascular coupling mechanisms in the cerebral cortex. The present results indicate that the number of days after birth is more closely related to development of auditory system and neuro-vascular coupling than is postconceptional age. Thus, this suggests that early extrauterine environment affects the cortical responses to verbal stimulation in preterm infants.

Relationship between cerebral oxygenation and phosphorylation potential during secondary energy failure in hypoxic-ischemic newborn piglets.

The aim of this study was to evaluate the hypothesis that cerebral hemoglobin (Hb) oxygenation is related to phosphorylation potential during primary and secondary cerebral energy failure in newborn infants who have experienced birth asphyxia. We subjected newborn piglets to severe transient cerebral hypoxic-ischemia followed by resuscitation and examined cerebral energy metabolism by 31P-magnetic resonance spectroscopy and evaluated changes in cerebral Hb oxygen saturation (ScO2) using full-spectrum near-infrared spectroscopy before, during, and up to 54 h after the hypoxic-ischemic insult. ScO2 was significantly decreased during the hypoxic-ischemic insult compared with baseline values. During secondary energy failure, piglets were separated based on the relationship between the ratio of phosphocreatine to inorganic phosphate and ScO2; those with a negative correlation were less injured than those with a positive correlation. These results indicate that changes in ScO2 as measured by near-infrared spectroscopy are related to phosphorylation potential during secondary energy failure in asphyxiated infants.

In vitro production of bilirubin photoisomers by light irradiation using neoBLUE

Background: The light‐emitting diode is used as one of the new light sources for phototherapy. NeoBLUE (Atom Medical, Tokyo, Japan) incorporates blue light‐emitting diodes for the treatment of neonatal hyperbilirubinemia. The authors compared the in vitro efficacy of neoBLUE with conventional phototherapy devices.

Change of bilirubin photoisomers in the urine and serum before and after phototherapy compared with light source

Background : The clinical effect of phototherapy for neonatal hyperbilirubinemia is based on the production and elimination of cyclobilirubin. Generally, the clinical effect of light sources is estimated by the reduction in the total serum bilirubin level. One procedure with less invasiveness than blood collecting is urine collection. Whether the effectiveness of light sources used for phototherapy could be assessed using measurements of bilirubin photoisomers in urine was studied.

Estimation of cerebral blood flow in a newborn piglet model of neonatal asphyxia.

Hypoxic ischemic encephalopathy (HIE) in newborn infants is one of the causes of later serious brain damage. In recent years, hypothermia therapy has attracted attention as an effective means of for preventing HIE-induced brain damage and has been used clinically 1, 2,3. However, the problem of which newborn infants should be selected for hypothermia therapy remains unsolved. Currently, selection is based on results of various tests such as neurological tests, blood biochemical tests and electroencephalography (EEG) 4. However, there is no definitive evaluation method.