To investigate the neuroanatomical regions and eletrophysiological spreading patterns responsible for faciobrachial dystonic seizures (FBDS) in leucine-rich glioma inactivated 1 (LGI1)-antibody encephalitis using magnetoencephalography (MEG).
FBDS in LGI1-antibody encephalitis presents with brief dystonic contractions of face-limb, sometimes accompanied by dizziness spell or piloerection sense. Although FBDS is presumed to have an epileptogenic origin, little is known about its neuroanatomic localization and how this brief semiology is generated. MEG enables 3D localization of epileptiform discharges and visualization of their spreading direction.
Simultaneous MEG (306 channels) and EEG (64 channels) recordings were performed using the TRIUXTM Neo system. LGI1-antibody encephalitis patients with frequent FBDS were enrolled. Video recording of patients was taken during the MEG to confirm the presence of FBDS events. Magnetic source localization was conducted using single and/or multiple Equivalent Current Dipole Models.
A total of 6 patients (mean age 52.7±14.5) completed the study (mean recording time 3.3±0.6 hours), and all patients had active FBDS or brief spells during the recordings. Epileptic discharges were recorded in 5 patients, localizing to several lateral cortical regions, including the mid-temporal, insula, parietal, and occipital regions. Representative discharges primarily spread in temporo-parietal direction, either activating the faciobrachial homunculus of motor cortex (FBDS), the insula (dizziness spell), or sensory cortex (abnormal sensations). Nevertheless, MEG was not fully sensitive in detecting all the FBDS activities, or many of the events lacked clear ictal discharges.
Short epileptic discharges spreading across the lateral cortex, primarily involving the faciobrachial homunculus of the motor cortex might explain the motor phenomenon of FBDS in LGI1-antibody encephalitis. Cortical irritability in insular and parietal lobes also might account for the dizziness or goosebump sensory phenomenon.