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Advanced Neurology Subcortical fibers in band heterotopia

were calculated. Unfortunately, this method included In all areas, a thin belt of white matter was interposed
15
parts of the band heterotopias in both patients; however, to between the heterotopia and the overlying cortex. In both
avoid rater-induced bias for comparison between patients cases, the cortex overlying the heterotopia was pachygyric
and controls, using individually drawn region of interest with coarse folding. Coregistered FA maps revealed
(ROI) appeared more reliable. increased intensities within the heterotopic bands, and
in patient 2, these intensities in some areas appeared as
The number of tracts was recorded, and DTI parameters
such as fractional anisotropy (FA), mean diffusivity (MD), extensions of the CentWM crossing the heterotopic mass
(Figure 1C and D).
longitudinal diffusivity (LD), and radial diffusivity (RD)
were taken from the abovementioned ROIs and compared 2.5. General tractography and SCWM and CentWM
with the parameters of the control group. Finally, individual tracts of patients 1 and 2 and controls
ROIs were interactively placed into the gray matter bands In both patients, the course of most streamlines generated
of the patients, and DTI parameters were recorded from via general tractography appeared to be “interrupted”
these ROIs. by the heterotopias, and only a small number of tracts
Differences between patients and controls were “passed” through the bands (Figure 2).
examined by the Mann–Whitney U-test for significance Long corticospinal tracts or radiation of the corpus
(P < 0.05). This test is not parametric but uses ranks callosum did not pass the band in patient 1 and had more
instead of means to estimate differences between groups lumpish peripheral extensions than those in a control case
and does not afford homogeneity of group variances. Thus, (Figure 3).
the number of group members does not affect the result.
Editing subgroups of tracts by the introduction of
Functional MRI of patient 2 was performed using a no-go areas, such as the previously segmented cortex or
30-s block design of motor, speech, and visual paradigms CentWM, showed that the number of subcortical tracts
and evaluated via Statistical Parametric Mapping (SPM, significantly reduced (P = 0.030), and they appeared to be
https://www.fil.ion.ucl.ac.uk/spm). Activated ROIs were packed more loosely in patients than in controls (Table 1).
used as seeding areas for fiber tracking. Conversely, the reduction in the number of CentWM tracts
in patients remained slightly below the level of significance
2.4. Result of T1-weighted images and FA maps of (P = 0.076). DTI parameters obtained from SCWM and
patients 1 and 2 and controls
CentWM ROIs were not significantly different between the
Patient 1 exhibited a continuous band of the subcortical two groups.
gray matter of varying diameters extending through both
hemispheres from frontal to occipital (Figure 1A), whereas 2.6. Tracts and DTI parameters generated from
in patient 2, heterotopy was confined to the parieto- heterotopias of patients 1 and 2
occipital areas and appeared band-like only in some In both patients, seeding ROIs placed into and strictly
regions, but was more voluminous in others (Figure 1B). confined to the heterotopias gave origin only to a small

A B C D

Figure 1. Magnetic resonance imaging. T1-weighted images (A and B) and FA maps (C and D). Patient 1 showed a band heterotopia extending throughout
both hemispheres, whereas in patient 2, the heterotopia was confined to the parieto-occipital region. In both cases, FA maps showed increased signal
within the bands, which appeared to be more structured in patient 2, particularly on the right (D). A subcortical area free from gray matter was clearly
visible in patient 1, but it could be identified as a small strip of white matter in patient 2. The overlying cortex appeared pachygyric.
Abbreviation: FA: Fractional anisotropy.

Volume 4 Issue 3 (2025) 112 doi: 10.36922/an.4823