fMEG - the clinical point of view
Fetal MEG is a unique method to record directly nondistorted magnetic fields corresponding to electrical currents that are generated in the human fetus as in neurons or myocardial cells. Therefore fMEG offers the first time a non-invasive insight into functional fetal brain development. Basic understanding of neuro-cognitive development can be achieved as described above.
Furthermore this approach provides a very useful tool for pregnancy surveillance to monitor fetal neurological development. This was not accessible in obstetrics so far.
But the brain is highly vulnerable especially to oxygen deprivation as in fetuses suffering chronic hypoxia due to placental insufficiency. Those kids are not only intrauterine growth restricted (IUGR) and burdened with higher perinatal morbidity and mortality. It is known that these infants are at risk of deranged neurological and cognitive long-term outcome (Leitner et al. 2007).
First fMEG-studies on IUGR fetuses showed a delayed latency decrement of auditory evoked responses (AER) during gestation compared to normal fetuses and indicated that AER could serve as a marker for functional fetal brain development (Kiefer et al. 2008).
- Figure 1: AER at 33. weeks of gestational age (left to right). Above: the evoked response (AER) as potential-peak (y-axes in femtoTesla) per time (x-scale in ms). Below left side: the corresponding magnetic field - visible as red-blue dipole in the sensor array. Below middle: AER-potentials in the channels of the sensor array.
The clinical research on the fMEG in Tübingen focuses to establish norm values of evoked brain responses during gestation in healthy fetuses in comparison with those at risk of constricted brain development. A major project focuses on the longitudinal monitoring of IUGR-fetuses and is funded by the DFG.
Another valuable magnetic field is the fetal heart signal. fMEG records the fetal cardiac activity in high temporal resolution and sensitivity. This provides the exact acquisition of the exact heart rate in R-R-intervals which is superior to the CTG-registration. Fetal heart rate serves as a marker of fetal well being. The high resolution of the fetal heart rate variability (HRV) in MEG-recordings provides new aspects for fetal monitoring. Parameters of sympathetic-parasympathetic balance can be observed as HRV-frequency spectra or quantifications of R-R-interval-differences. The influence and alterations of the vegetative system can be determined. This could be useful to monitor fetal well-being as well as fetal activity or resting states.
Out of the magnetic cardiac signal a so called magentocardiogramm (MCG) can be obtained. This is an equivalent to the known ECG. Beside the rhythmicity the physiological information of the cardiac function is available. This offers a new diagnostic insight in fetal heart function, especially if arrhythmic beats are assumed. With MCG the physiological development of cardiac activity currents can be received even in early gestational weeks starting with the second trimester and could help to varify and classify fetal arrhythmias (Strasburger et al. 2010).
- Figure 2: Fetal cardiac activity as fMCG-curve with a bipolar P-wave, QRS-complex and T-wave.
MCG-studies are ongoing at the fMEG-Center in Tübingen to standardize MCG acquisition and cardiac time interval values during gestation in uncomplicated pregnancies and those with the risk of fetal arrhythmias.
The collaboration between the fMEG-Center and the department of obstetrics and gynecology provides the favorable condition of the clinical research integrating reserach with the clinical support expertise of the departments taking care of the recruted probands.
Principal investigator
Dr med Isabelle Kiefer
http://www.uni-frauenklinik-tuebingen.de/bereiche/praenataldiagnostik/fmeg.html
References
Leitner Y, Fattal-Valevski A, Geva R, Eshel R, Toledano-Alhadef H, Rotstein M, Bassan H, Radianu B, Bitchonsky O, Jaffa AJ, Harel S. Neurodevelopmental outcome of children with intrauterine growth retardation: a longitudinal, 10-year prospective study. J Child Neurol. 2007; 22(5):580-7.
Kiefer I., Siegel E., Preissl H., Ware M., Schauf B., Lowery C., Eswaran H. Delayed maturation of Auditory evoked responses in Growth-restricted fetuses revealed by magnetoencephalographic recordings. Am J Obstet Gynecol. 2008 Nov;199(5):503.e1-7. Epub 2008 Jun 4.
Strasburger JF, Wakai RT.Fetal cardiac arrhythmia detection and in utero therapy.Nat Rev Cardiol. 2010 May;7(5):277-90
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