The spatial extent of fast ripples is associated with cognitive and language deficits in children with focal epilepsy: An exploratory SEEG study
Marco Dallavalle1, Nicolás von Ellenreider2, Jenny Bellerose3
1Montreal Children's Hospital, 1001 Decarie Boulevard, Montreal, Quebec H4A 3J1, Canada; University of Pavia, Corso Strada Nuova 65, 27100 Pavia, Italy.
Objective:
To determine if the spatial extent of interictal fast ripples in focal epilepsy patients is associated with brain dysfunction.
Methods:
Thirty pediatric focal epilepsy patients who underwent SEEG investigation had their cognitive and language deficits assessed in scales of 0 to 4. Fast ripples (250-500 Hz), ripples (80-250 Hz), and IEDs were automatically detected in 10 min during NREM sleep. We fitted linear models to the relationship between the cognitive deficit scale and the spatial spread of the interictal neurophysiologic events (number of channels with rate of events > 10 % of maximum rate). For the language deficit, we computed the Spearman correlation between the median rate of events in all brain regions and the deficit scale.
Results:
Cognitive deficit scale was significantly associated with the number of channels with fast ripples (p = 0.049), not so with ripples (p = 0.31), IEDs (p = 0.31). The potential confound of number of explored channels did not improve the fitting of the models. Language deficits were not correlated with the number of channels showing interictal events. However, from all brain regions the most statistically significant correlations (p < 0.01) were between median fast ripple rates in the left and right pars opercularis and triangularis of the inferior frontal gyrus (Broca's area and its contralateral counterpart) with r = 0.66, p = 0.003 (18 patients), in the superior temporal gyrus in the language dominant hemisphere with r = 0.72, p = 0.005 (13 patients), and the dominant basal temporal region with r = 0.79, p = 0.006 (10 patients). Median rates of IEDs and ripples exhibited lower correlation with language deficits in these regions.
Conclusion:
Widespread fast ripples are associated with increased cognitive deficits, and language deficiencies are correlated with fast ripple rates in brain regions associated with language. The extent of fast-ripple activity was associated with cognitive deficit severity in this cohort, whereas the corresponding associations for ripples and IEDs did not reach statistical significance.
