Magnetic resonance signal intensity measurements in the diagnosis of fetal central nervous system anomalies

Abstract

Objectives: To evaluate the possible role of Magnetic Resonance (MR) signal intensity measurements in diagnosing Central Nervous System (CNS) anomalies antenatally. Methods: MR images of 110 fetal brains between 18 and 38 weeks were studied. Nine were excluded due to destroyed brain. 50 had CNS anomalies. 51 had normal CNS and were used as controls. Regions of interest (ROI) cursors were placed in Vitreous, cerebellar vermis, thalamus, frontal white matter, corona radiata, periventricular region and grey matter. The lateral ventricle diameters were also obtained. Signal intensity ratio (SIR) was calculated by the signal intensity of each of the above regions to that of the vitreous. SIR in controls were compared with fetuses having: (1) Hydrocephalus. (2) Arnold Chiari type-2 Malformation (ACM-2) (3) Non-progressive ventriculomegaly (4) Miscellaneous CNS anomalies. The correlation of the normalcy or abnormalcy of the brain was based on Clinical/Physical examination in 51, Ultrasound in 20, MRI in 2 and autopsy in 28. Results: In hydrocephalus and ACM-2, the SIR of vermis and periventricular region were higher than controls whereas in non-progressive ventriculomegaly and miscellaneous CNS anomalies there was no significant difference. Conclusion: Signal intensity measurements are useful to differentiate physiological and non-progressive ventriculomegaly from hydrocephalus and ACM-2.