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Advanced Neurology Subcortical fibers in band heterotopia

with a more severely affected phenotype than heterozygous behavior and reduced mobility of her right extremities.
women, wherein neurons expressing the non-mutated Her EEG showed bifrontal spike-wave discharges. The scan
gene might migrate appropriately. had to be performed under general anesthesia.

Clinically, patients with SBH exhibit a wide Patient 2 was a 22-year-old woman who started
spectrum of features. Typical symptoms include mental experiencing tonic–clonic convulsions at the age of
retardation and high seizure rates, depending on the 12 years and presented with episodes of “loss of look and
degree of manifestation of the heterotopia. Invasive absentia.” Her EEG revealed frequent interictal spike-wave
4,5
electroencephalogram (EEG), single photon emission discharges. Under lamotrigine and valproic acid treatment,
computed tomography, and experimental data suggest her seizure rate could be reduced to 2 – 5 episodes/month.
that the heterotopia and overlying cortex contribute to the She had no neurologic or neurologic deficit and worked
development of epilepsy. Accordingly, no specific EEG successfully as a psychologist.
6-9
patterns have been described in the literature. 10
2.2. MRI
Early and recent magnetic resonance imaging (MRI)
studies using tractography have shown a rather “isolated” All scans were performed using a 3T Philips Achieva
band caused by interruptions of central or more peripheral scanner and included the following sequences:
white matter tracts at the inner respective outer border of • T1-weighted: 3D turbo field echo MPRAGE, repetition
the SBH. 11-13 Thus, epileptic discharges from the overlying time/echo time (TR/TE) = 6.73/3.11 ms, number of
3
cortex might be difficult to propagate to generalization. sagittal slices = 180, reconstructed voxel size = 1 mm .
However, according to histology, this “isolation” does not • DTI: Number of gradient directions = 32, b = 0 and
appear to be real. “All subtypes of inhibitory GABAergic 800 s/mm², measured voxel size = 2 × 2 × 2 mm,
interneurons intermingled with pyramidal neurons were number of slices covering the whole head = 60, SENSE
observed in the white matter. This network of differentiated factor = 2.
neurons with its dendritic and axonal ramifications • Functional MRI (patient 2 only): Echo planar
suggests the presence of functional neuronal circuitry, and imaging–gradient echo sequence: TR = 2000 ms,
there is strong observational evidence that the two cortices number of slices with 3-mm thickness = 34, gap =
were anatomically and functionally interconnected.” 14, p.1838 0.75 mm, field of view = 192 mm, voxel size = 2.38 ×
2.38 × 2 mm, and number of slices covering the whole
Owing to this ostensible discrepancy between imaging head = 34.
and post-mortem findings, we examined the subcortical
white matter (SCWM) between the malformation and 2.3. Post-processing of data
overlying cortex and between the central white matter Post-processing of DTI data was performed using the
(CentWM) and longer tracts as well as explored the program “MRtrix3” (https://www.mrtrix.org), supported
organization of the malformation using diffusion tensor by “FSL” (FMRIB Software Library, https://fsl.fmrib.ox.ac.
imaging (DTI)–based tractography. uk/fsl). MRtrix uses multishell multitissue constrained

2. Case series spherical deconvolution to improve fiber tracking in
voxels containing crossing fibers and partial volume
The retrospective study had been approved by the local effect, anatomically constrained tractography to reject
ethics committee of CEDIMAT, and informed consent was streamlines ending in biologically implausible tissues
obtained from each participant. such as the cerebrospinal fluid (CSF), and spherical
deconvolution informed filtering of tractograms, which
2.1. Controls and patients 1 and 2 corrects the overestimation of longer streamlines.
Overall, 2 patients with drug-resistant epilepsy, in whom DTI data from images arranged in stacks were denoised
MRI revealed an SBH, and 10 healthy age-matched and corrected for ringing artifacts and EPI distortion, and
volunteers (control group), who had undergone MRI fiber distribution orientation was then estimated. The
previously for other reasons, were enrolled. T1-weighted images were segmented into tissue types such

Patient 1 was a 24-year-old woman who had been as gray matter, CentWM, and CSF and coregistered to the
suffering from tonic and rarely from clonic seizures since DTI. For general tractography, streamlines were calculated
the age of 13 years. Her seizure rate initially reached from the coregistered gray matter–white matter border
up to 50/day, which was reduced by a combination of templates for the whole brain. Tracts within the SCWM
carbamazepine, valproic acid, and lacosamide. Cognitively, were edited from these streamlines by excluding all tracts
she had mental retardation with spells of aggressive that entered into the CentWM. Vice versa, CentWM tracts

Volume 4 Issue 3 (2025) 111 doi: 10.36922/an.4823