PMC9232187_01
MRI images. Pre- (A) and 6 month post-treatment MRI (B) showing left occipital cortical thickening and blurring of gray-white junction, implying the presence of a focal cortical dysplasia. The pre-treatment cortical enhancement resolved at the follow-up study.
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Brain MRI showed a focal cortical dysplasia in the left occipital lobe with surrounding cortical enhancement (Figure 1A).
TMS targeting. Stereotactic TMS targeting using the patient's MRI in 3 planes (top) and 3D model (bottom). The dipole of the TMS pulses is indicated, with the arrows indicating the direction of the induced electric field (red cathodal, blue anodal).
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EEG monitoring (Figure 2). MRI-based stereotaxis assisted in precise targeting and stimulus delivery over the 5-day period. Each day starting at ~1 pm in the afternoon, 1,800 pulses of 1 Hz stimulation were provided over 30 mins.
Spectral power density and ratios. Median spectral power density and power ratios. (A) Median spectral power density across all channels. There is an inflection point around 2 Hz, with lower frequencies showing more power after stimulation initiation. (B) Ratio of slow delta activity to faster delta activity, showing a significant increase in median power by the end of stimulation as compared to prior. (C) Broadband power, again showing a significant difference in median by the end of stimulation therapy as compared to before. Asterisks indicate statistical significance by Wilcoxon rank-sum test as compared to prior to stimulation (day 0).
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He was admitted to the Epilepsy Monitoring Unit (EMU), where focal seizures were recorded occurring 7-8 times per hour (nearly 200 seizures per day), arising maximally from the left occipital head region near electrode O1 (Figure 3A). There was a gradual improvement in seizure frequency and duration over his 8-day hospitalization (Figure 3). Automated seizure detections decreased over the course of therapy (Figure 3). Broadband spectral power from 2 to 20 Hz was gradually decreased with stimulation (Figure 3C), also with a significant difference in medians by the fifth day of stimulation (p < 0.0001 by Wilcoxon rank sum test). These changes were coincident with improvement in seizure frequency (Figure 3).
Timeline.
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He has returned five times for additional rTMS treatments, for a mean follow-up interval of every 3.4 months (Figure 4).
EEG and seizure frequency. EEG seizure onset and automated seizure detections. (A) EEG seizure onset on longitudinal bipolar montage. EEG settings: low frequency filter 7 Hz, high frequency filter 70 Hz, sensitivity 7 uV/mm. (B) 16-h segments showing automated seizure detections (red bars) prior to stimulation; after 5 days of stimulation; and 1 month after TMS. (C) Percentage of time spent in seizure, showing an initial 22% increase after medication load, followed by day-by-day reduction after TMS treatment began.
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Median power per frequency bin across all channels was plotted for the day prior to TMS therapy, the day stimulation began, and on the last day of the initial TMS therapy (Figure 5A). Upon review of the day-by-day EEG power, we noticed an inflection point around 2 Hz; on this basis, similar to previous research (Lundstrom et al.,), we compared the ratio of 0.5-2 Hz infraslow activity to 2-4 Hz delta activity (Figure 5B).