Myo-inositol metabolism in appropriately grown and growth-restricted fetuses: a proton magnetic resonance spectroscopy study.

OBJECTIVE: Myo-inositol (Myo-ins) is a marker of neuroglial cells, being present in the astrocytes of brain tissue, but also functions as an osmolyte. Numbers of astrocytes are known to increase following injury to the brain. Growth-restricted fetuses are at increased risk of later neurodevelopmental impairments even in the absence of overt lesions and despite preserved/increased cerebral blood flow. This study aims to investigate brain Myo-ins metabolism in fetuses with intrauterine growth restriction (IUGR) and evidence of cerebral redistribution using magnetic resonance spectroscopy (MRS) at a short echo time. STUDY DESIGN: Biometry and Doppler assessment of blood flow was assessed using ultrasound in 28 fetuses with IUGR and 47 appropriately grown control subjects. MRI was used to exclude overt brain injury. Proton magnetic resonance spectroscopy of the fetal brain was then performed at an echo time of 42 ms to examine the Myo-ins:Choline (Cho), Myo-ins:Creatine (Cr) and Cho:Cr ratios. RESULTS: No alterations in brain Myo-ins:Cho, Myo-ins:Cr or Cho:Cr ratios were detected between appropriately grown and growth restricted fetuses. CONCLUSIONS: IUGR is not associated with a measureable difference in brain myo-inositol ratios. This may be due to the protective effects of preserved cerebral blood flow in growth restriction and comparable astrocyte numbers when compared to controls.

Foetal volumetry using magnetic resonance imaging in intrauterine growth restriction.

OBJECTIVES: We used magnetic resonance imaging (MRI) to perform volumetry of foetuses with and without growth restriction, and identify deviations in organ growth. STUDY DESIGN: 20 growth restricted and 19 normal foetuses were scanned once during pregnancy at gestational age 20.53-36.57 weeks. MRI scans were performed on a 1.5T system using ssFSE sequences. Manual segmentation of whole body, brain, heart, lung, liver, thymus and kidney volume was performed. Data on the severity of foetal growth restriction and pregnancy outcome was collected. RESULTS: There was a significant reduction in foetal whole body volume and volume of all internal organs except the brain in growth restricted foetuses. A brain:liver ratio above 3.0 was associated with a 3.3 fold increase in risk of perinatal mortality (95% CI=1.68-6.47). CONCLUSION: MRI provides an accurate assessment of foetal organ growth. It may have a role to play in monitoring disease severity and the effect of future interventions.

Brain metabolism in fetal intrauterine growth restriction: a proton magnetic resonance spectroscopy study.

OBJECTIVE: The purpose of this study was to investigate alterations in brain metabolism in fetuses with intrauterine growth restriction (IUGR) and evidence of cerebral redistribution of blood flow. STUDY DESIGN: Biometry and Doppler assessment of blood flow was assessed with ultrasound in 28 fetuses with IUGR and cerebral redistribution and in 41 appropriately grown control subjects. Proton magnetic resonance spectroscopy of the fetal brain was then performed to determine the presence of choline (Cho), creatine (Cr), N-acetylaspartate (NAA), and lactate and to generate ratios for NAA:Cho, NAA:Cr, and Cho:Cr. RESULTS: Sixty-five percent of spectra were interpretable: N-acetylaspartate, choline, and creatine peaks were identified in all these spectra; lactate was present in 5 IUGR fetuses and in 3 appropriately grown fetuses. NAA:Cr and NAA:Cho ratios were significantly lower in IUGR fetuses with cerebral redistribution. CONCLUSION: Cerebral redistribution is associated with altered brain metabolism that is evidenced by a reduction in NAA:Cho and NAA:Cr ratios.

Proton magnetic resonance spectroscopy in the fetus.

Magnetic Resonance Imaging (MRI) has become an established technique in fetal medicine, providing complementary information to ultrasound in studies of the brain. MRI can provide detailed structural information irrespective of the position of the fetal head or maternal habitus. Proton Magnetic Resonance Spectroscopy ((1)HMRS) is based on the same physical principles as MRI but data are collected as a spectrum, allowing the biochemical and metabolic status of in vivo tissue to be studied in a non-invasive manner. (1)HMRS has been used to assess metabolic function in the neonatal brain but fetal studies have been limited, primarily due to fetal motion. This review will assess the technique and findings from fetal studies to date.