Location of periventricular nodular heterotopia is related to the malformation phenotype on MRI

Abstract

Background and purpose: Periventricular nodular heterotopia are common malformations of cortical development that are associated with many clinical syndromes and with many different neuroimaging phenotypes. The purpose of this study was to determine whether specific malformation phenotypes may be related to location, side, or number of PNH as assessed by MR imaging.

Materials and methods: MR images of 200 patients previously diagnosed with PNH were retrospectively analyzed. PNH were classified according to their location along the ventricles (anterior, posterior, or diffuse), side (unilateral or bilateral), and number of nodules (<5, 6-10, or >10). The cerebrum, brain stem and cerebellum were analyzed to assess associated anomalies. Associations between PNH location and the presence of other anomalies were tested by using Fisher exact test and χ2 test.

Results: Posterior PNH were significantly associated with malformations of the cerebral cortex, diminished white matter volume, and mid-/hindbrain anomalies. Diffuse PNH were associated with diminished white matter volume, callosal "anomalies," and the presence of megacisterna magna. Unilateral PNH were strongly associated with cortical malformations.

Conclusions: Certain malformation complexes are associated with PNH in specific locations: posterior PNH with cerebral cortical and mid-/hindbrain malformations and diffuse PNH with callosal anomalies and megacisterna magna. Knowledge of these associations should allow more directed analyses of brain MR imaging in patients with PNH. In addition, knowledge of these associations may help to direct studies to elucidate the causes of these malformation complexes.

Fig. 1.

PNH main patterns evaluated with T1 inversion recovery–weighted image. Arrowheads show locations of heterotopia. Axial images show an aPNH pattern with nodules restricted to the frontal horns (A) and bodies (B). Axial images demonstrate a pPNH pattern. Nodules are lining trigones and temporal and occipital horns bilaterally (C), sparing the frontal horns and bodies (D). E and F, Axial images show a dPNH pattern with nodules lining all of the walls of the lateral ventricles.

Fig. 2.

pPNH and malformations of cortical development. Axial T2 FSE images show PNH lining the wall of the right temporal and occipital horns and trigone (arrowheads in A) and a large region of subcortical heterotopia in the right frontoparietal region (asterisks in B). C, Coronal T1 inversion recovery–weighted image demonstrates bilateral PNH in the temporal horns (arrowheads) and bilateral parietal pachygyria (arrows). D, Coronal inversion recovery–weighted image shows right temporal PNH (arrowheads) and bilateral perisylvian polymicrogyria (white arrows). E and F, Axial T1 inversion recovery–weighted images demonstrate bilateral pPNH (arrowheads) and a left occipital schizencephaly (asterisk in E). White arrows in F show the thickness of the WM band measured between the most posteromedial margin of Sylvian fissure and the lateral border of the ventricular trigone. In this case, it was diminished (5 mm).

Fig. 3.

Heterotopia and commissure anomalies. T1 inversion recovery–weighted images in a 12-year-old boy with dPNH on the right cerebral hemisphere. A, Right parasagittal image shows multiple PNH lining the entire margin of the lateral ventricle. B, Sagittal image demonstrates agenesis of the corpus callosum with a thick anterior commissure (arrowhead) and an anteriorly positioned hippocampal commissure (arrow). A vascular structure is running along of the top of the third ventricle (open arrowhead). C, Coronal image shows moderate white matter volume reduction in the right hemisphere. The fornices are properly located at the roof of the third ventricle (arrows). PNH is seen in the margin of the frontal and temporal horns (arrowheads).

Fig. 4.

pPNH and posterior fossa anomalies. A and B, An 11-day-old boy with microcephaly. Small PNH are present in the trigones (black arrowheads in A [axial T2 spin-echo–weighted image]). Other findings include a small pons (p in B [sagittal T1 spin-echo–weighted image]), a hypoplastic and dysmorphic vermis (white arrowheads), and a large inferior cerebellar peduncle (arrow). C and D, A 2-year-old boy with PNH in the trigones (black arrows in C [coronal T1 inversion recovery–weighted image]) and a very small vermis (white arrowheads), dysplastic and small cerebellar hemispheres (black arrowheads), and megacisterna magna (MCM).