Combining sodium MRI, proton MR spectroscopic imaging, and intracerebral EEG in epilepsy

Mikhael Azilinon (1, 2, 3, 4) , Julia Makhalova (1, 2, 3, 4) , Wafaa Zaaraoui (1, 2) , Samuel Medina Villalon (4, 3) , Patrick Viout (1, 2) , Tangi Roussel (1, 2) , Mohamed M El Mendili (1, 2) , Ben Ridley (5) , Jean-Philippe Ranjeva (1, 2) , Fabrice Bartolomei (4, 3) , Viktor Jirsa (4, 3) , Maxime Guye (1, 2)

1 CRMBM - Centre de résonance magnétique biologique et médicale
2 CEMEREM - Centre d'Exploration Métabolique par Résonance Magnétique [Hôpital de la Timone - APHM]
3 INS - Institut de Neurosciences des Systèmes
4 Service d'Epileptologie et de Rythmologie Cérébrale [Hôpital de la Timone, AP-HM]
5 IRCCS Istituto delle Scienze Neurologiche di Bologna [Bologna, Italy]

Whole brain ionic and metabolic imaging has potential as a powerful tool for the characterization of brain diseases. We combined sodium MRI (23 Na MRI) and 1 H-MR Spectroscopic Imaging (1 H-MRSI), assessing changes within epileptogenic networks in comparison with electrophysiologically normal networks as defined by stereotactic EEG (SEEG) recordings analysis. We applied a multi-echo density adapted 3D projection reconstruction pulse sequence at 7 T (23 Na-MRI) and a 3D echo-planar spectroscopic imaging sequence at 3 T (1 H-MRSI) in 19 patients suffering from drugresistant focal epilepsy who underwent presurgical SEEG. We investigated 23 Na MRI parameters including total sodium concentration (TSC) and the sodium signal fraction associated with the short component of T 2 * decay (f), alongside the level of metabolites N-acetyl aspartate (NAA), choline compounds (Cho), and total creatine (tCr). All measures were extracted from spherical regions of interest (ROIs) centered between two adjacent SEEG electrode contacts and z-scored against the same ROI in controls. Group comparison showed a significant increase in f only in the epileptogenic zone (EZ) compared to controls and compared to patients' propagation zone (PZ) and noninvolved zone (NIZ). TSC was significantly increased in all patients' regions compared to controls. Conversely, NAA levels were significantly lower in patients compared to controls, and lower in the EZ compared to PZ and NIZ. Multiple regression analyzing the relationship between sodium and metabolites levels revealed significant relations

Mots clés: ultrashort echo time; voltage-gated sodium channel; fluorodeoxyglucose PET; hydrogen; sodium; anterior commissure-posterior commissure; achieved significance level; choline compounds; CRLB; Cramer-Rao lower bound; DNET; dysembryoplastic neuroepithelial tumor; EAAT; glutamate transporter; extracellular volume; Epileptogenicity Index; EPSI; echoplanar spectroscopic imaging; epileptogenic zone; fraction of sodium signal with short T 2 * decays; focal cortical dysplasia; FDR; false discovery rate; FOV; field of view; GRAPPA; GeneRalized Autocalibrating Partial Parallel Acquisition; HC; healthy control; MIDAS; Metabolite Imaging and Data Analyses System; MNI; Montreal Neurological Institute; MP2RAGE; magnetization prepared 2 rapid acquisition gradient echo; MPRAGE; magnetization prepared rapid acquisition gradient echo; Na+/K+ pump; sodium potassium pump; N-acetyl aspartate; apparent concentrations of sodium with long T2* decays; apparent concentrations of sodium with short apparent T2* decay; bicarbonate sodium cotransporter; sodium calcium exchanger; sodium hydrogen antiporter; noninvolved zone; sodium potassium chloride cotransporter; pH; potential of hydrogen; propagation zone; region of interest; stereotactic EEG; sodium longT 2 * relaxation time; sodium short T 2 * relaxation time; total creatine; echo time; inversion time; repetition time; total sodium concentration

Domaines: Imagerie

Mikhael Azilinon, Julia Makhalova, Wafaa Zaaraoui, Samuel Medina Villalon, Patrick Viout, et al.. Combining sodium MRI, proton MR spectroscopic imaging, and intracerebral EEG in epilepsy. Human Brain Mapping, In press, ⟨10.1002/hbm.26102⟩. ⟨hal-03811157⟩