Fetal Brain MRI: Novel Classification and Contribution to Sonography

Abstract

Purpose: 1) To evaluate and classify the indications for fetal brain MRI in a tertiary referral center. 2) To assess the contribution of fetal brain MRI to fetal neurosonography.

Materials and Methods: A retrospective study in a tertiary medical center during a two-year period (2011 – 2012) included pregnant women who underwent fetal brain MRI. MRI was implemented at 32 weeks of gestation unless a severe abnormality possibly requiring earlier medical intervention was suspected.

Results: 633 patients were included, 40 (6.3 %) underwent repeated examinations with a total of 733 fetal MRI scans. Patients were classified to three main indication cohorts: Suspected primary brain anomaly (52.9 %), non-CNS disorders (32.5 %) and obstetrical complications (14.6 %). These cohorts were further divided into 16 separate groups with lateral ventricle abnormalities being the most common (23.7 %), followed by exposure to TORCH (17.5 %) and cerebral cortex abnormalities (13 %). 149 (19.3 %) fetal MRI scans demonstrated additional findings. Repeated examinations were commonly implemented in complicated monochorionic-biamniotic (MCBA) twin pregnancies (34.6 %) and in cases of supra-tentorial cysts (19 %). The average gestational age for MRI scan in the MCBA group was 26 ± 5 weeks in comparison to ≥ 31st weeks in all other groups (p < 0.001).

Conclusion: The current study describes a detailed picture of fetal brain MRI indications. Most patients were referred because of CNS anomalies. The impressive diversity of 16 separate entities emphasizes the expanding use of fetal brain MRI. Complicated MCBA pregnancies, which may have dramatic events, constitute a unique challenge due to early and repetitive MRI examinations and may serve as a role model for the contribution of fetal MRI during antenatal evaluation. The contribution of MRI to prenatal evaluation in various indications is discussed.

Zusammenfassung

Ziel: 1) Bewertung und Klassifizierung der Indikationen für eine MRT des fetalen Gehirns in einem Tertiärzentrum. 2) Die Bewertung der MRT des fetalen Gehirns unterstützend zur Neurosonografie.

Material und Methoden: Eine retrospektive Studie in einem medizinischen Tertiärzentrum schloss Schwangere über einen Zeitraum von 2 Jahren (2011 – 2012) ein, bei denen eine fetale MRT des Gehirns erfolgte. Die MRT wurde in der 32. Schwangerschaftswoche durchgeführt, wenn nicht aufgrund des Verdachts auf schwere Anomalien eine frühere medizinische Intervention nötig war.

Ergebnisse: Eingeschlossen wurden 633 Patienten mit insgesamt 733 fetalen MRT-Untersuchungen, davon 40 (6,3 %), bei denen wiederholt Untersuchungen durchgeführt wurden. Die Patienten wurden nach der Hauptindikation in drei Kohorten eingeteilt: Verdacht auf primäre Hirnanomalien (52,9 %), Erkrankungen ohne ZNS-Beteiligung (32,5 %) und geburtshilfliche Komplikationen (14,6 %). Diese Kohorten wurden in 16 verschiedene Untergruppen eingeteilt, wobei die häufigsten Auffälligkeiten Anomalien der Seitenventrikel (23,7 %), Exposition zu TORCH-Erregern (17,5 %) und Anomalien der Hirnrinde (13 %) waren. Bei den fetalen MRT-Untersuchungen wurden in 149 Fällen (19,3 %) zusätzliche Befunde erhoben. Folgeuntersuchungen wurden im Allgemeinen in schwierigen monochoriotisch-diamniotischen (MCDA) Zwillingsschwangerschaften (34,6 %) und in Fällen mit supratentoriellen Zysten (19 %) durchgeführt. Das durchschnittliche Schwangerschaftsalter bei MRT-Untersuchung in der MCDA-Gruppe betrug 26 ± 5 Wochen im Vergleich zu ≥ 31. SSW in allen anderen Gruppen (p < 0,001).

Schlussfolgerung: Die vorliegende Studie beschreibt ein detailliertes Bild der Indikationen für eine MRT des fetalen Gehirns. Die meisten Patienten wurden aufgrund von lokalisierten ZNS-Auffälligkeiten untersucht. Die beeindruckende Vielfalt von 16 unterschiedlichen Untergruppen unterstreicht den zunehmenden Einsatz der MRT des fetalen Gehirns. Schwierige MCDA-Schwangerschaften, die dramatische Verläufe haben können, sind eine ganz besondere Herausforderung aufgrund der frühen und wiederholten MRT-Untersuchungen. Sie können als Vorbild dienen, was den Beitrag der fetalen MRT bei der vorgeburtlichen Analyse anbelangt. Die Leistung der MRT für die pränatale Bewertung bei verschiedenen Indikationen wird diskutiert.

Key words

brain - CNS - MR imaging

• References

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