Miguel E. Fiol

De novo mutations in epileptic encephalopathies

Epileptic encephalopathies are a devastating group of severe childhood epilepsy disorders for which the cause is often unknown. Here we report a screen for de novo mutations in patients with two classical epileptic encephalopathies: infantile spasms (n = 149) and Lennox–Gastaut syndrome (n = 115). We sequenced the exomes of 264 probands, and their parents, and confirmed 329 de novo mutations. A likelihood analysis showed a significant excess of de novo mutations in the ∼4,000 genes that are the most intolerant to functional genetic variation in the human population (P = 2.9 × 10−3). Among these are GABRB3, with de novo mutations in four patients, and ALG13, with the same de novo mutation in two patients; both genes show clear statistical evidence of association with epileptic encephalopathy. Given the relevant site-specific mutation rates, the probabilities of these outcomes occurring by chance are P = 4.1 × 10−10 and P = 7.8 × 10−12, respectively. Other genes with de novo mutations in this cohort include CACNA1A, CHD2, FLNA, GABRA1, GRIN1, GRIN2B, HNRNPU, IQSEC2, MTOR and NEDD4L. Finally, we show that the de novo mutations observed are enriched in specific gene sets including genes regulated by the fragile X protein (P < 10−8), as has been reported previously for autism spectrum disorders.

Language function after temporal lobectomy without stimulation mapping of cortical function.

Summary We studied 95 patients who underwent standard anterior temporal lobectomy (ATL) without stimulation mapping of language areas, using neuropsychological parameters of language function preoperatively and 1 year postoperatively [Boston Naming Test and Verbal Fluency, and the Information, Comprehension, Arithmetic, Similarities, Digit Span, and Vocabulary subtests of the Wechsler Adult Intelligence Scale (WAIS)]. Verbal IQ (VIQ), Performance IQ (PIQ), Full‐scale IQ (FSIQ), and Verbal Deviation Quotient were also evaluated, as were parameters of memory function. All patients had hemisphere dominance for language assessed by an intracarotid amytal test. Fifty‐three patients had a left dominant (LHDL) ATL with a mean extent of lateral resection of 4.8 cm, and 10 had a left ATL with right or mixed hemisphere dominance (RHDL, MDL). Thirty‐two patients had a right nondominant ATL. Seizure outcome was 57 and 59% seizure‐free for LHDH and right nondominant group, respectively, 1 year after operation. Comparison of preoperative scores showed the LHDL group to have significantly lower scores than the right nondominant group for several parameters of language function and memory. The group undergoing left dominant ATL showed no significant loss of language function postoperatively and actually showed gains in many parameters. Standard ATL without stimulation mapping of language areas and with conservative lateral resection is safe for long‐term language function. In addition, evidence shows preexisting language dysfunction in patients undergoing left dominant ATL.

The prognostic value of residual spikes in the postexcision electrocorticogram after temporal lobectomy.

We correlated the postresection electrocorticograms (ECoGs) of 80 patients who underwent temporal lobectomy under general anesthesia for treatment of intractable complex partial seizures with surgical results in three groups: seizure/aura free (32 patients), auras only (16 patients), and one or more postoperative seizures (32 patients) at mean follow-up times of 34, 31, and 38 months, respectively. Spontaneous “residual spikes,” ie, present after all resections, were present in 47% of patients who had no postoperative seizures or auras. However, they occurred in 72% of patients with any postoperative seizures (p <0.05). The location (convexity, mesial, or edge of resections) or the distribution (unifocal versus multifocal) of the residual spikes was not of prognostic value. Quantitative studies in 5-minute epochs of the postexcision ECoGs did not reveal a significant difference in the morphology of the residual spikes, ie, the amplitude or firing pattern (single versus polyspike), in the three groups. The group with postoperative seizures showed a higher number of spikes per epoch (≥50), but it was not significant. Although the study shows that patients with residual spikes may have good prognosis, they are at significantly higher risk for postoperative seizures as compared with those without residual spikes. The possibility that intensity of firing of residual spikes may be an additional predictor of outcome warrants further study.

Ultra-rare genetic variation in common epilepsies: a case-control sequencing study

BACKGROUND Despite progress in understanding the genetics of rare epilepsies, the more common epilepsies have proven less amenable to traditional gene-discovery analyses. We aimed to assess the contribution of ultra-rare genetic variation to common epilepsies. METHODS We did a case-control sequencing study with exome sequence data from unrelated individuals clinically evaluated for one of the two most common epilepsy syndromes: familial genetic generalised epilepsy, or familial or sporadic non-acquired focal epilepsy. Individuals of any age were recruited between Nov 26, 2007, and Aug 2, 2013, through the multicentre Epilepsy Phenome/Genome Project and Epi4K collaborations, and samples were sequenced at the Institute for Genomic Medicine (New York, USA) between Feb 6, 2013, and Aug 18, 2015. To identify epilepsy risk signals, we tested all protein-coding genes for an excess of ultra-rare genetic variation among the cases, compared with control samples with no known epilepsy or epilepsy comorbidity sequenced through unrelated studies. FINDINGS We separately compared the sequence data from 640 individuals with familial genetic generalised epilepsy and 525 individuals with familial non-acquired focal epilepsy to the same group of 3877 controls, and found significantly higher rates of ultra-rare deleterious variation in genes established as causative for dominant epilepsy disorders (familial genetic generalised epilepsy: odd ratio [OR] 2·3, 95% CI 1·7-3·2, p=9·1 × 10-8; familial non-acquired focal epilepsy 3·6, 2·7-4·9, p=1·1 × 10-17). Comparison of an additional cohort of 662 individuals with sporadic non-acquired focal epilepsy to controls did not identify study-wide significant signals. For the individuals with familial non-acquired focal epilepsy, we found that five known epilepsy genes ranked as the top five genes enriched for ultra-rare deleterious variation. After accounting for the control carrier rate, we estimate that these five genes contribute to the risk of epilepsy in approximately 8% of individuals with familial non-acquired focal epilepsy. Our analyses showed that no individual gene was significantly associated with familial genetic generalised epilepsy; however, known epilepsy genes had lower p values relative to the rest of the protein-coding genes (p=5·8 × 10-8) that were lower than expected from a random sampling of genes. INTERPRETATION We identified excess ultra-rare variation in known epilepsy genes, which establishes a clear connection between the genetics of common and rare, severe epilepsies, and shows that the variants responsible for epilepsy risk are exceptionally rare in the general population. Our results suggest that the emerging paradigm of targeting of treatments to the genetic cause in rare devastating epilepsies might also extend to a proportion of common epilepsies. These findings might allow clinicians to broadly explain the cause of these syndromes to patients, and lay the foundation for possible precision treatments in the future. FUNDING National Institute of Neurological Disorders and Stroke (NINDS), and Epilepsy Research UK.

Outcome of resective surgery for intractable partial epilepsy guided by subdural electrode arrays

The aim of this paper was to evaluate the outcome and the factors predictive for a good prognosis of resective surgery for intractable partial epilepsy guided by subdural electrode arrays (SEAs) and operative electrocorticography. Sixty‐four patients, aged 8–52 years, were evaluated with chronic SEAs in order to record interictal and ictal activity and delineate speech and motor areas by functionally mapping. Resection were individualized to each patients SEA recorded electrocorticogram and operative electrocorticogram and functional mapping results (tailored resection). The follow‐up time was a minimum of one year. Good seizure outcome was defined as seizure free from complex partial and secondary generalized seizures. After one year 70% of the patients with a temporal ictal focus was seizure free compared to 55% of the patients with an extratemporal focus. Complete resection of interictal or ictal fields as mapped with SEAs, gave better prognosis than partial resection. Patients with no postresection spikes had a better prognosis than patients with residual postresection spikes evaluated with operative electrocorticography. Sex, age, duration of epilepsy prior to surgery, extent of temporal lobe resection and structural abnormalities determined by MRI were not associated with a favorable seizure outcome after surgery. We conclude that complete resection of the interictal and ictal field mapped with SEAs and absence of postresection spikes on operative electrocorticography are associated with an excellent seizure outcome.

Language function following subdural grid-directed temporal lobectomy

The purpose of the study was to determine the extent to which a temporal resection may be undertaken without producing risk to temporal language areas. Patients undergoing craniotomy and placement of a subdural electrode array (SEA) for evaluation of intractable epilepsy were studied to determine the variability of distance of temporal language cortex from the temporal pole. Hemisphere dominance was determined by intracarotid sodium amytal injection. Temporal lobe speech arrest (SA) was mapped with a 64 contact point SEA. Thirty‐one patients had left dominant hemisphere SEAs. Thirty had SA 5 cm to 9 cm from the temporal pole (median 7 cm). One had SA at 3 cm. Twenty‐one patients subsequently had temporal lobectomy (TL). Mean extent of resection was 5.7 cm (range 3 to 9 cm). In 18 TL patients who had neuropsychometric evaluation of language function pre‐ and post‐surgery, there was no significant deterioration. Thirty‐nine patients had right non‐dominant SEAs placed. Eighteen had TL. Thirteen of these had pre‐ and post‐surgery language evaluation and there was no significant change. Comparison of preoperative scores showed significant superiority of the right non‐dominant group over the left dominant group for naming. TL up to 5 cm without stimulation mapping of language areas would be safe in the majority of cases, but one subject (3%) had SA mapped anterior to this and a small number of cases may therefore be at risk to language function following a 5 cm TL. Extensive lateral resections up to 9 cm are possible with preservation of language function with stimulation cortical mapping.

Effect of isoflurane (Forane) on intraoperative electrocorticogram.

Isoflurane, an inhalation agent often used for general anesthesia during craniotomy, has been reported to suppress spike activity in the intraoperative electrocor‐ticogram (ECoG) during epilepsy surgery. We studied the effect of isoflurane concentrations of 0.25, 0.5, 0.75, 1, and 1.25% on the number of spike bursts per 5‐min epochs in 15 patients undergoing ECoG during epilepsy surgery. N2O in O2 was maintained at 50% in 10 patients, at 60% in 2, and at 70% in 3. End tidal CO2 concentration was maintained in the hypocarbic range, and analgesia was maintained with the narcotic alfentanil in the range of 0.5–2 μg/kg/min. The median number of spikes for each isoflurane concentration was 29 (range 3–107) at 0.25%, 27 (range 2–73) at 0.5%; 29 (range 5–90) at 0.75%, 33 (range 2–100) at 1%, and 40 (range 32–140) in 5 patients who tolerated 1.25% without occurrence of burst suppression pattern. No significant difference (Students paired t test) was noted in the number of spikes for each isoflurane concentration. Therefore, if isoflurane concentrations are maintained between 0.25 and 1.25% or before burst suppression pattern occurs and N2O/O2 is maintained in the 50–70% range, isoflurane has no significant effect on spike activity.

Value of Intraoperative EEG Changes During Corpus Callosotomy in Predicting Surgical Results

Summary: The intraoperative transformation of generalized epileptiform discharges (GED) to lateralized epileptiform activity during the course of corpus callosum sectioning for intractable epilepsy in 37 patients was correlated with percentage of decrease in atonic‐tonic seizures with “drops” at mean follow‐up of 26 months (range 12– 86 months). Twenty‐seven (73%) patients had intraoperative interictal discharges, and 21 (78%) showed varying degrees of lateralization of GED during corpus callosum sectioning (two thirds to total). All patients experienced >80% reduction in atonic‐tonic seizures with drops. The group (n = 7) with largest decrease in GED had the greatest decrease in seizures (95.5%). Six patients without change in GED had 88% decrease in seizures, as did 14 patients (85–86%) with mild or moderate decreases in GED, but there was no statistically significant correlation between decrease in GED and seizure frequency after operation. Thus, although lateralization of GED after corpus callosum sectioning was evident in 78% of patients with GED, the degree of lateralization of GED did not correlate with degree of reduction of tonic‐atonic seizures. Therefore, intraoperative surface EEG monitoring does not appear to be helpful at this time as a guide to extent of callosotomy.

Copy number variant analysis from exome data in 349 patients with epileptic encephalopathy

Infantile spasms (IS) and Lennox–Gastaut syndrome (LGS) are epileptic encephalopathies characterized by early onset, intractable seizures, and poor developmental outcomes. De novo sequence mutations and copy number variants (CNVs) are causative in a subset of cases. We used exome sequence data in 349 trios with IS or LGS to identify putative de novo CNVs. We confirm 18 de novo CNVs in 17 patients (4.8%), 10 of which are likely pathogenic, giving a firm genetic diagnosis for 2.9% of patients. Confirmation of exome‐predicted CNVs by array‐based methods is still required due to false‐positive rates of prediction algorithms. Our exome‐based results are consistent with recent array‐based studies in similar cohorts and highlight novel candidate genes for IS and LGS. Ann Neurol 2015;78:323–328

Eating epilepsy : EEG and clinical study

Summary: We studied a 22‐year‐old woman with eating epilepsy. During 52 days, her seizures were monitored in an inpatient epilepsy center, and their relation to meals, foods, and other variables was assessed. Of a total of 136 seizures observed, 76 occurred during eating and 60 occurred at noneating times. Observation during 6 h of video monitoring detected a rate of type A seizures (head drop, generalized EEG activity) of 1.0 during eating epochs versus 0.21 during noneating epochs (p < 0.05). Interictal generalized EEG activity consisting of sharp slow‐wave complexes was also markedly increased during eating epochs, with mean 16.6 discharges per epoch versus 2.89 during noneating epochs (p < 0.02). AED levels remained stable during monitoring. Dietary analysis indicated that many types of food seemed to be implicated and that some specific foods were repeated activators.