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 63-year-old right-handed woman with VNS implantation 6 years prior to her MEG recording presented for further evaluation. Since age 18 months old the patient had focal seizures with impaired awareness and occasional evolution to bilateral convulsive seizures. Her auras were typified by staring off, ringing in her ears, and a nauseated feeling. The patient experienced feelings of déjà vu prior to bilateral convulsive seizures. Prior EEG evaluation had revealed bitemporal interictal spikes, more frequent over the left than the right hemisphere. Seizures were captured and appeared electrographically generalized. The patient had a choroid cyst adjacent to her right hippocampus, but otherwise the MRI of her brain was unremarkable. Primidone, lacosamide, and lamotrigine had not provided adequate seizure control. An MEG recording, beamformed with SAM(g2), indicated widespread activity with a left lateral temporal as well as left lateral frontal activity and a left mesial occipital–parietal focus. Source signal series from these areas displayed no evidence of VNS artifact and had an SNR of at least 35:1 for the interictal spikes relative to baseline activity.\nBased on information obtained from her EEG and MEG recordings, the patient underwent invasive monitoring. Bilateral subdural strips were placed in the orbitofrontal, lateral temporal, and inferior temporal regions. Bilateral depth electrodes were also placed in the amygdale and anterior and posterior hippocampi. Because, a resection of the occipital/parietal focus would have likely resulted in deficits, it was not covered by grids or strips.\nThe invasive monitoring captured six seizures arising from the right hemisphere and seven seizures arising from the left hemisphere. Of this total, five events were electrographic seizures and two were electro-clinical seizures. The monitoring revealed that the patient had independent seizures arising from broad fields in both hemispheres. On this basis, it was felt that the patient was a poor surgical candidate for seizure reduction or freedom, and the grids and strips were explanted.