Assessment of the Deep Gray Nuclei in Holoprosencephaly

Erin M. Simon; Robert Hevner; Joseph D. Pinter; Nancy J. Clegg; Van S. Miller; Stephen L. Kinsman; Jin S. Hahn; A. James Barkovich

Article Figures & Data

Figures

Tables

Download figure
Open in new tab
Download powerpoint
fig 1.
Range of noncleavage of the basal ganglia and thalamus.
A, Grade 0: Axial T2-weighted image at the level of the third ventricle shows the abnormally deep anterior IHF (long arrow) and widely separated caudate and lentiform nuclei (short arrows).
B, Grade 1: Axial T2-weighted image at the level of the third ventricle shows the medial location and small amount of contact between the caudate nuclei (arrow). Note also the noncleavage of the claustra (arrowheads) and probable anterior limbs of the internal capsules (white matter posterior to claustra).
C, Grade 2: Axial T2-weighted image in a more severely affected patient shows the partial noncleavage of the lentiform nuclei (white arrows) and thalami (black arrows).
D, Grade 3: Coronal 3D spoiled gradient-echo image through the caudate heads shows complete failure of cleavage (arrows).
Download figure
Open in new tab
Download powerpoint
fig 2.
Range of noncleavage of the hypothalamus.
A, Grade 1: Coronal T2-weighted image shows the attenuated anterior recess of the third ventricle (arrow) in the setting of partial hypothalamic noncleavage.
B, Grade 2: Coronal T1-weighted image shows the continuity of the hypothalamus across the midline of the basal forebrain (short arrow). Note the associated ectopic neurohypophysis (long arrow).
fig 3. Deep gray nuclear mass. Axial T1-weighted image shows the noncleaved deep gray nuclear mass, which is diminished in volume and without discernible structures (arrows)
Download figure
Open in new tab
Download powerpoint
fig 4.
Spatial orientation of the thalami.
A, Grade 0: Axial T2-weighted image shows the thalami with their long axes at an angle approximately 30° to 45° relative to the plane of the IHF (arrows).
B, Grade 1: Axial T2-weighted image shows the thalami with their long axes approximately parallel to the plane of the IHF (arrows).
C, Grade 2: Axial T2-weighted image shows the thalami with their long axes approximately perpendicular to the plane of the IHF (arrows).
Download figure
Open in new tab
Download powerpoint
fig 5.
Diagrams of the developing prosencephalon.
A, Superior view of the neural plate, with the top being the rostral end at the anterior neuropore and the bottom being more caudal at the level of the diencephalon. Adapted from (25) with permission from the Annual Review of Neuroscience, Volume 21, 1998.
B, Lateral view of the neural plate, with the floor plate (fp) at the bottom and the roof plate (rp) at the top. Adapted from (24) with permission from The Company of Biologists, Ltd.
C, Coronal view of the neural plate with the roof plate (rp) (dorsal) at the top and the floor plate (fp) and prechordal plate (pcp) (ventral) at the bottom.
The more rostral and alar portion, superiorly (above the horizontal dashed black line in A) and to the left (anterior to the vertical dashed black line in B) is the secondary prosencephalon (sp) whereas the more inferior (in A) and right-sided portion (in B) is the diencephalon (di). The longitudinal gray area represents the prechordal plate. The horseshoe-shaped dashed black line surrounding the prechordal plate (in A) represents the boundary between the basal (or ventral) plate (ba) and the alar (or dorsal) plate (al). Within the secondary prosencephalon, structures at all dorsal and ventral levels are affected. The basal midline regions closest to the floor plate and to the lateral ventricles are the most severely affected in HPE. The reason for this is illustrated in C. In normal embryonic development, an interplay of dorsalizing molecules (emanating from the roof plate) and ventralizing molecules (emanating from the prechordal plate and floor plate) modulates regional identity of tissues along the dorsoventral axis of the neural tube. Either a lack of production of ventralizing factors or an overproduction of dorsalizing factors can result in noncleavage (commonly called fusion) of structures that normally lie just lateral to the midline. This is the presumed mechanism by which HPE develops. nh indicates neurohypophysis; hy, hypothalamus; ey, eyefields; gp, globus pallidus; am, amygdala; ac, anterior commissure; lt, laminal terminalis; st, striatum (caudate and putamen); cx, cortex; hi, hippocampus; se, septum; po, preoptic nucleus; ob, olfactory bulb; bst, bed nucleus of stria terminalis.