A 21-year-old man with an onset of seizures in 2004 presented for further evaluation. He had one febrile seizure in infancy and has a history of headaches. His events consisted of staring off for a few minutes, being unaware of surroundings, and exhibiting abnormal behavior and incomprehensible speech. He felt tired afterwards and typically had an aura of a right frontal headache. The patient’s seizure frequency was 1–2 per week, and his longest seizure-free interval was two years. The patient had tried multiple antiseizure medications but his seizures were insufficiently controlled under them. During a subsequent EMU admission, scalp EEG recorded several seizures originating in the left temporal region, and his interictal EEG was notable for occasional left temporal slowing and left temporal epileptiform activity. Ictal SPECT exhibited left occipital and left temporal hyperperfusion during one of these seizures, and a later interictal SPECT uncovered two possible anterior and posterior left temporal foci that were considered worrisome for seizure foci. The PET scan was negative. Structural MRI indicated a possible subtle form of hippocampal malrotation as well as two small foci of T2 hyperintensity in the bilateral frontal white matter that were nonspecific, but were thought to be the sequelae of prior ischemia, inflammation/infection, trauma or demyelination. In contrast, the patient’s MEG scan revealed a left occipital focus (A) with hundreds of MEG-only spikes visible on the virtual electrode (B). Based on the collective results, the patient received invasive monitoring with inter-hemispheric and left lateral occipital grids and left temporal depth electrodes. ICEEG confirmed the left occipital MEG focus as the seizure generator. The patient had a left occipital resection and had a few seizures shortly after surgery in the setting of medication nonadherence. Following this, he has been seizure-free for over a year.
A 40-year-old right-handed man with VNS implantation 7 years prior to the MEG recording presented for further evaluation. He had received a right anterior temporal lobectomy 2 years prior to MEG recording. Since age 2 years old the patient has had focal seizures with an autonomic aura and evolution to bilateral convulsive seizures. Multiple seizures were captured during EMU monitoring and which could only be lateralized to the right hemisphere. An MRI of his brain demonstrated only his prior resection, and SPECT did not identify a seizure focus. SAM(g2) analysis of his MEG recording revealed a right posterior lateral parietal focus just dorsal to the lateral fissure whose spatial extent included posterior parts of the superior and middle temporal gyri. This activity was located slightly above the resection margin. The SNR for this source signal series was >20:1, although the interictal spikes present in the source signal series did not have a clear EEG correlate during the simultaneous recording.