Rationale:
This study aims to present a compelling case demonstrating unique capacity of magnetoencephalography (MEG) to detect frequent epileptiform discharges (EDs) that were missed by electroencephalography (EEG), thus primarily reshaping the planning for epilepsy surgery. MEG and EEG, both non-invasive neuroimaging techniques, play essential roles in pre-surgical evaluations in patients with epilepsy, with MEG offering superior spatial resolution. Unlike EEG, MEG remains unaffected by signal distortion through the skull and scalp. Notably, prior studies have shown superiority of MEG over conventional EEG in detecting smaller cortical activation areas (Kharkar et al.,
Epilepsy & behavior, 2015).
Methods:
We conducted an assessment on a 24-year-old patient diagnosed with cerebral palsy, who had a history of right middle cerebral artery (R-MCA) stroke, resulting in encephalomalacia and residual left hemi-body spasticity. The patient also presented a history of complex partial seizures, which commenced at the age of 15, characterized by episodes of staring spells accompanied by speech difficulties and postictal symptoms. The initial evaluation in the Epilepsy Monitoring Unit (EMU) indicated a likely seizure focus originating in the right temporal lobe, and associated mesial temporal sclerosis. The patient underwent concurrent MEG and EEG examinations at the University of Florida Health. These assessments aimed to localize EDs and facilitate functional mapping.
Results:
Based on video-EEG, MRI, and PET results from the EMU stay, right temporal seizures with a primarily subclinical nature and mesial versus lateral cortical origin were hypothesized. However, the MEG findings revealed frequent EDs, many of which had eluded detection in EEG recordings (
Figure 1). These EDs clustered in two regions: one in the superior parietal area and another in the posterior aspect of the superior frontal lobe, both situated in the superior periphery of the R-MCA (see
Figures 1). Remarkably, these EDs went unnoticed during the EMU workup. Additionally, another type of EDs, corresponding to rhythmic delta activity, was observed in both MEG and EEG. These were localized in the right mesial temporal lobe, aligning with EMU findings.
Conclusions:
This case exemplifies the exceptional capacity of MEG to detect and precisely localize EDs, surpassing the capabilities of other neuroimaging and electrodiagnostic tools. The MEG findings profoundly influenced the course of surgical planning and treatment for the patient, enabling the localization of discharges that EEG failed to detect. It also provides valuable guidance for surgeons in case they plan to place intracranial electrodes to achieve precise seizure localization, ultimately aiming for complete seizure freedom. The absence of MEG in this case would have significantly altered the patient's treatment trajectory, highlighting the importance of employing a diverse range of modalities for comprehensive seizure diagnosis and management. Furthermore, the integration of MEG into non-invasive evaluations promises a more holistic approach to understanding and treating epilepsy, benefiting both clinicians and patients.
Funding: None