The value of resting-state functional magnetic resonance imaging for detecting epileptogenic zones in patients with focal epilepsy

Abstract

Objective: To determine the value of resting-state functional magnetic resonance imaging (RS-fMRI) based on the local analysis methods regional homogeneity (ReHo), amplitude of low-frequency fluctuations (ALFF), and fractional ALFF (fALFF), for detecting epileptogenic zones (EZs).

Methods: A total of 42 consecutive patients with focal epilepsy were enrolled. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of visually assessed RS-fMRI, MRI, magnetic resonance spectroscopy (MRS), video electroencephalography (VEEG), and positron-emission tomography computed tomography (PET-CT) in EZ localization were evaluated to assess their diagnostic abilities. ReHo, ALFF, and fALFF were also compared for their diagnostic values.

Results: RS-fMRI showed comparable sensitivity to PET (83.3%) and specificity to VEEG (66.7%), respectively, for EZ localization in patients with focal epilepsy. There were no significant differences between RS-fMRI and the other localization techniques in terms of sensitivity, specificity, PPV, and NPV. The sensitivities of ReHo, ALFF, and fALFF were 69.4%, 52.8%, and 38.9%, respectively, and for specificities of 66.7%, 83.3%, and 66.7%, respectively. There were no significant differences among ReHo, ALFF, and fALFF, except that ReHo was more sensitive than fALFF.

Conclusions: RS-fMRI may be an efficient tool for detecting EZs in focal epilepsy patients.

Fig 1. Left parieto-occipital lobe dysplasia in a MRI negative 9-year-old patient.

(A) Axial and (E) sagittal fALFF, (B) axial ALFF, and (C) ReHo reveal abnormal activation in the left parieto-occipital lobe. (D) The corresponding ¹⁸F-FDG PET/CT image shows low FDG uptake in the left frontoparietal region. (F) Pathological confirmation of left parieto-occipital lobe focal cortical dysplasia.

Fig 2. A 38-year-old man diagnosed with right lateral temporal lobe epilepsy.

(A) Coronal fALFF, (B) ALFF, and (C) ReHo reveal abnormal activation in the right lateral temporal lobe. An area of activation could also be found in the corpus callosum, which is considered a part of the default mode network. (D) The corresponding ¹⁸F-FDG PET/CT image reveals low FDG uptake in the right lateral temporal lobe region. (E) VEEG depiction of interictal epileptiform discharges of right temporal lobe.

Fig 3. A 42-year-old woman diagnosed with right mesial temporal lobe epilepsy.

(A) Coronal T1-weighted image showing right hippocampus atrophy, (B) FLAIR image showing slightly high signal of right hippocampus. (C) ¹⁸F-FDG PET/CT imaging reveals low FDG uptake in the left temporal lobe region, particularly, in the hippocampus. (D) Coronal ALFF and (E) ReHo reveal abnormal activation in the right hippocampus compared to the left side. (F, G) VEEG showing ictal and interictal discharges in the right temporal lobe.