Authors :
Presenting Author: Pradeep Javarayee, MD MBA – The Medical College of Wisconsin, Milwaukee
Daniel Ackom, MS – Marquette University and Medical College of Wisconsin Joint Department of Biomedical Engineering
Ricardo Vega, MS – Marquette University and Medical College of Wisconsin Joint Department of Biomedical Engineering
Kayleigh Butler, MS – Medical College of Wisconsin
Andrew Crow, BA – The Medical College of Wisconsin, Milwaukee
Brian Schmit, PhD – Marquette University and Medical College of Wisconsin Joint Department of Biomedical Engineering
Scott Beardsley, PhD – Marquette University and Medical College of Wisconsin Joint Department of Biomedical Engineering
Irene Kim, MD – Medical College of Wisconsin
Sean Lew, MD – Children's Wisconsin, Medical College of Wisconsin
Rationale: In pediatric refractory epilepsy, functional hemispherectomy (FH) is performed to treat patients with widespread unilateral epileptogenic activity. However, structural adaptations or remote degeneration within the contralateral (spared) hemisphere remain insufficiently understood. Quantifying gray matter (GM) and white matter (WM) volume changes in the spared hemisphere may offer insights into compensatory remodeling and adaptive structural reorganization within preserved regions to support redistributed neurological functions.
Methods:
Patients who underwent FH at Children’s Wisconsin (2012–2023) were included. Pre- (≤1 month) and post-op (6–12 months) T1-weighted MRIs were processed using the CAT12 longitudinal pipeline to generate modulated GM and WM maps of the spared hemisphere. A standardized mask excluded midline and resection areas. Total GM and WM volumes were calculated from modulated intensities, and relative volume change was expressed as percent difference normalized to pre-op values. One-sample t-tests assessed mean volume change (α = 0.05), and Spearman correlation tested GM–WM change associations. Voxel-wise and ROI analyses were precluded by anatomical distortion; individual maps were qualitatively reviewed for localized changes.
Results:
All patients who underwent FH between 2012 and 2023 were screened, with 9 of 56 meeting inclusion criteria based on sufficient imaging; the final cohort (mean surgical age 8.4 years) comprised 9 patients (ages 1–13 years; 5 males), including 6 left-sided and 3 right-sided FH cases. Etiologies included perinatal cerebrovascular accident (n = 4), Sturge-Weber syndrome (n = 1), hemimegalencephaly (n = 1), and focal cortical dysplasia (n = 1) (Table 1). Contralateral WM volumes demonstrated considerable intersubject variability: three patients exhibited substantial reductions (up to –30.4%), three showed notable increases (up to +20.2%), and three remained relatively stable (within ±5%) (Figure 1, Table 1). GM volumes showed a similar distribution, ranging from marked decreases (up to –12.8%) to increases (up to +15.5%) or minimal change (±1%). One patient exhibited the most pronounced WM and GM increases, whereas another showed the greatest WM loss accompanied by moderate GM decline (Figure 1, Table 1). There was no significant correlation between the relative change in GM volume and either time since surgery (p = 0.460, R² = 0.068) or age at seizure onset (p = 0.576, R² = 0.075). Similarly, the relative change in WM volume was not significantly associated with time since surgery (p = 0.546, R² = 0.099) or age at seizure onset (p = 0.606, R² = 0.037).
Conclusions:
Post-FH, the spared hemisphere shows highly variable WM and GM changes. Some patients exhibit volume increases (possibly indicating neuroplasticity), others decrease (possibly indicating degeneration), offsetting each other at the group level. Thus, mapping individual neuroanatomical trajectories may be helpful to predicting outcomes and guiding personalized rehabilitation.
Funding: None