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Clinical Features, Neuropathology, and Surgical Outcome in Patients With Refractory Epilepsy and Brain Somatic Variants in the SLC35A2 Gene

. 2023 Jan 31 ; 100 (5) : e528-e542. [epub] 20221028

Language English Country United States Media print-electronic

Document type Multicenter Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't

Grant support
R01 NS114122 NINDS NIH HHS - United States
R01 NS115017 NINDS NIH HHS - United States
P50 HD105351 NICHD NIH HHS - United States
R01 NS089552 NINDS NIH HHS - United States
R01 NS117544 NINDS NIH HHS - United States
R01 NS094596 NINDS NIH HHS - United States
R21 NS101303 NINDS NIH HHS - United States

Links

PubMed 36307217
PubMed Central PMC9931085
DOI 10.1212/wnl.0000000000201471
PII: WNL.0000000000201471
Knihovny.cz E-resources

BACKGROUND AND OBJECTIVES: The SLC35A2 gene, located at chromosome Xp11.23, encodes for a uridine diphosphate-galactose transporter. We describe clinical, genetic, neuroimaging, EEG, and histopathologic findings and assess possible predictors of postoperative seizure and cognitive outcome in 47 patients with refractory epilepsy and brain somatic SLC35A2 gene variants. METHODS: This is a retrospective multicenter study where we performed a descriptive analysis and classical hypothesis testing. We included the variables of interest significantly associated with the outcomes in the generalized linear models. RESULTS: Two main phenotypes were associated with brain somatic SLC35A2 variants: (1) early epileptic encephalopathy (EE, 39 patients) with epileptic spasms as the predominant seizure type and moderate to severe intellectual disability and (2) drug-resistant focal epilepsy (DR-FE, 8 patients) associated with normal/borderline cognitive function and specific neuropsychological deficits. Brain MRI was abnormal in all patients with EE and in 50% of those with DR-FE. Histopathology review identified mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy in 44/47 patients and was inconclusive in 3. The 47 patients harbored 42 distinct mosaic SLC35A2 variants, including 14 (33.3%) missense, 13 (30.9%) frameshift, 10 (23.8%) nonsense, 4 (9.5%) in-frame deletions/duplications, and 1 (2.4%) splicing variant. Variant allele frequencies (VAFs) ranged from 1.4% to 52.6% (mean VAF: 17.3 ± 13.5). At last follow-up (35.5 ± 21.5 months), 30 patients (63.8%) were in Engel Class I, of which 26 (55.3%) were in Class IA. Cognitive performances remained unchanged in most patients after surgery. Regression analyses showed that the probability of achieving both Engel Class IA and Class I outcomes, adjusted by age at seizure onset, was lower when the duration of epilepsy increased and higher when postoperative EEG was normal or improved. Lower brain VAF was associated with improved postoperative cognitive outcome in the analysis of associations, but this finding was not confirmed in regression analyses. DISCUSSION: Brain somatic SLC35A2 gene variants are associated with 2 main clinical phenotypes, EE and DR-FE, and a histopathologic diagnosis of MOGHE. Additional studies will be needed to delineate any possible correlation between specific genetic variants, mutational load in the epileptogenic tissue, and surgical outcomes.

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Neurology. 100(5):225. PubMed

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