Essential features of Chiari II malformation in MR imaging: an interobserver reliability study—part 1

Abstract

PurposeBrain MR imaging is essential in the assessment of Chiari II malformation in clinical and research settings concerning spina bifida. However, the interpretation of morphological features of the malformation on MR images may not always be straightforward. In an attempt to select those features that unambiguously characterize the Chiari II malformation, we investigated the interobserver reliability of all its well-known MR features.MethodsBrain MR images of 79 children [26 presumed to have Chiari II malformation, 36 presumed to have no cerebral abnormalities, and 17 children in whom some Chiari II malformation features might be present; mean age 10.6 (SD 3.2; range, 6-16) years] were blindly and independently reviewed by three observers. They rated 33 morphological features of the Chiari II malformation as present, absent, or indefinable in three planes (sagittal, axial, and coronal). The interobserver reliability was assessed using κ statistics.ResultsTwenty-three of the features studied turned out to be unreliable, whereas the interobserver agreement was almost perfect (κ value > 0.8) for nine features (eight in the sagittal plane and one in the axial plane, but none in the coronal plane).ConclusionsThis study presents essential features of the Chiari II malformation on MR images by ruling out the unreliable features. Using these features may improve the assessment of Chiari II malformation in clinical and research settings.

Fetal Cerebellar Vermis Assessment by MRI. What Does It Add?

“…turned out to be also helpful in differentiating two supratentorial entities as well; dance to what was stated in the study of NielsGeerdink., et al [20] Regarding the similarity in the results between the fetal MRI and the postnatal MRI; we came to a conclusion in our study that no demanding need for performing postnatal MRI for confirmation in cases of vermian abnormalities. That was in contrary to what was concluded by Limperopoulos et al, 2008 [2] in her study where she stated that their findings strongly support the need for postnatal MRI follow-up in cases with suspected posterior fossa anomalies by fetal MRI.…”

Diagnostic imaging of posterior fossa anomalies in the fetus and neonate: part 2, posterior fossa disorders

“…The mass effect also manifests with inferior displacement of the lower brainstem, a small and inferiorly displaced fourth ventricle, aqueductal stenosis, enlargement of the foramen magnum, and distorted stretching of the mesencephalic tectum ("tectal beaking"). Additional findings in the supratentorial brain often include dysplasia and hypoplasia of the corpus callosum, hydrocephalus, gyral malformations and interdigitation across the falx, and enlargement of the massa intermedia [28,32,33]. The calvarium may also be affected in a Chiari II malformation, with a mesenchymal dysplasia of the calvarial plates, leading to the "luckenschadel" or lacunar skull (Fig.…”

Reliability of MR Imaging–Based Posterior Fossa and Brain Stem Measurements in Open Spinal Dysraphism in the Era of Fetal Surgery

“…The midsagittal PF area was measured according to Tsai et al 20 The ventricular width (VW) was measured in the coronal plane according to Garel, 26 and in case of asymmetry, the largest value was taken into account. Mamillopontine distance, the level of kinking of the brain stem, medullary length, tentorial length, and width of the cisterna magna were measured as described by Geerdink et al 8 The width of the foramen magnum was defined as the distance between the opisthion and the basion. The cerebellar herniation level (CHL) was measured by drawing a perpendicular line from the foramen magnum to the lowest cerebellar portion.…”

“…6 The Chiari II malformation is characterized by posterior fossa (PF) and brain stem abnormalities with downward displacement and compression of the cerebellum and brain stem. 7 Geerdink et al 8 demonstrated that morphometric measures reliably quantify the morphologic distortions of Chiari II malformation on postnatal MR images. The mamillopontine distance and the cerebellar width were the most sensitive and specific de-terminants of Chiari II.…”

“…14,[16][17][18][19][20][21][22][23] These parameters have also been shown to change after in utero repair of OSD in small series and at different time points after fetal surgery, yet no study has consistently reported early postoperative assessment in utero. 18 The aims of this study were 3-fold: 1) to assess the reproducibility of measurements of the brain stem and PF that have been suggested to be representative on postnatal 8,9 and prenatal MR imaging 14,[16][17][18][19][20][21][22][23] ; 2) to apply those parameters that were shown to be reproducible, to discriminate fetuses with OSD from gestational age-matched fetuses with a normal PF; and 3) to document early changes in these measurements 1 week after a fetal operation.…”