A 31-year-old woman with spells preceded by visual symptoms of macropsia and micropsia and olfactory auras presented for further evaluation. Following the auras, the patient often exhibited right eye deviation and tonic flexion of the right upper extremities followed by a loss of awareness and generalized tonic-clonic events of 2–3 min in length. Afterwards, the patient experienced mild confusion and was tired for tens of minutes. She also had jerking of her arms and legs during sleep and the patient’s husband was unable to arouse her. The patient’s auras occurred every few days. She had 1–2 daytime spells a month, and she estimated that she had several more nighttime spells. These spells had been captured on routine EEG and during two EMU admissions and no electrographic change suggestive of seizure was noted. Neither a CT nor an MRI demonstrated any structural brain abnormalities. Treatment with several antiseizure medicines failed to provide adequate relief, and the patient had allergic reactions to some of the medicines. Despite the significant concern that her spells were nonepileptic in nature, given the severity of her events the patient received a diagnostic MEG scan.\nSAM(g2) identified three foci of epileptiform activity during her MEG scan: one focus in the left posterior temporal/lateral occipital cortex (A), and bilateral mesial temporal foci (not shown). The left posterior temporal/lateral occipital cortical focus was likely responsible for her visual symptoms, and the bilateral mesial temporal foci were likely responsible for her olfactory auras as the irritable zones encompassed entorhinal cortex. The irritability of the mesial temporal cortices was initially supported by bilateral sphenoidal electrodes, which detected interictal epileptiform activity. Importantly, MEG captured two seizures during the recording which originated within the posterior temporal/lateral occipital cortex, and neither of these seizures was discernable on EEG (B). Based on the MEG localizing information, ICEEG was performed as part of a presurgical evaluation. During a recorded seizure, ICEEG demonstrated early epileptiform activity (red channel, D) at electrodes (green) near the SAM(g2) peaks (red crosses, C). While ICEEG confirmed the localization of the three SAM(g2) foci, it also corroborated the MEG finding that the posterior temporal/lateral occipital focus was indeed the seizure initiator. Interestingly, the morphology of the ICEEG seizure was very similar to the morphology of the MEG seizure; both started with an initial spike, then exhibited a period of fast activity, and then evolved into a rhythmic discharge. Because the patient’s primary focus encompassed part of visual cortex, she decided against surgery to avoid a potential visual field defect. However, the MEG findings were still useful as they definitively identified the patient as having epilepsy. The patient is currently being considered for responsive neurostimulation device (RNS) placement.
A 47-year-old woman with VNS implantation 10 years prior to her MEG recording presented for further evaluation. The patient reported focal seizures with evolution to bilateral convulsive seizures since childhood. The patient’s baseline EEG was notable for bilateral, independent temporal spikes. Despite multiple admissions for EMU monitoring and several captured seizures, scalp EEG demonstrated only subtle changes that were neither localizing nor lateralizing. The patient’s MRI demonstrated right mesial temporal sclerosis, bilateral polymicrogyria located around the lateral fissures, and a left hemisphere closed-lip schizencephaly. Analysis of her MEG data by SAM(g2) revealed kurtotic activity that localized to left lateral parietal cortex just above the lateral fissure and extended down into the superior temporal gyrus. Importantly, this focus overlaps with the region of schizencephaly in the left parietal cortex. The source signal series for this focus had an SNR of about 35:1, although the interictal spikes present in the MEG recording did not have a clear EEG correlate.\nGiven the findings of right mesial temporal sclerosis and the probable multifocal nature of this patient’s epilepsy, this patient received a right temporal lobectomy without invasive monitoring with the goal of seizure reduction. Prior to her surgery, the patient had two to eight focal seizures with evolution to bilateral convulsive seizures monthly, and following resection no seizures have been reported although the patient continues to have likely non-epileptic spells.