The nucleus basalis of Meynert (NBM) may be the most perturbed network nodes among patients with temporal lobe epilepsy (TLE), according to study findings from a functional magnetic resonance imaging (fMRI) published in Neurology.
Patients (n=40) who underwent epilepsy surgery evaluation for unilateral mesial TLE at Vanderbilt University Medical Center were recruited for this study. Resting state fMRI findings were compared between patients and healthy control group participants (n=40). Patients and control group participants were 52.5% women and had a mean age of 38.5 years.
Patients were diagnosed with epilepsy at an average of 21.1 (range, 2-50) years previously. They reported 9.1 (range, 0-195) focal aware conscious seizures per month and 6.4 (range, 0-48) focal impaired-consciousness seizures per month. 55.0% had a history of focal to bilateral tonic-clonic seizures. During video-electroencephalography, results were well localized (ictal) in 87.5% and lateralized (interictal) in 65.0%. During positron electron tomography, 77.5% exhibited mesial temporal hypometabolism.
Compared with control group participants, patients had decreased connectivity between NBM and broad neocortical regions. The patients also had less connectivity between the NBM and the whole brain on both the ipsilateral (0.65±1.11 vs 2.13±1.43; P =9´10-6) and contralateral (1.18±1.10 vs 1.79±1.25; P =.03) sides, according to side of seizure onset. Patients had decreased connectivity between ipsilateral NBM and the frontoparietal cortex compared with control group participants (0.04±1.66 vs 1.47±2.05; P =.004, respectively).
Patients who had a higher frequency of consciousness-impairing focal seizures had greater decreases of connectivity between the NBM and frontoparietal cortex (r, -0.41; P =.008) than patients who had consciousness-sparing focal seizures (r, -0.13; P =.418).
In a clustering analysis, 95.5% of regional communities exhibited similar patterns between cohorts; however, NBMs clustered in differing communities among the control group participants and patients. These altered node strengths correlated with language abilities (r, 0.53; P <.001), attention and concentration (r, 0.39; P =.011), cognitive processing (r, 0.35; P =.035), and visual memory (r, 0.32; P =.039).
In a network analysis, the clustering coefficient of all nodes differed among patients and controls between NBM and both ipsilateral (2.23±0.93 vs 3.46±1.17; P =3.38´10-6) and contralateral sides (2.63±0.85 vs 3.32±1.12; P =.005), respectively.
Taken altogether, these data suggested the best fit model, which assumes an important connectivity of NBM ipsilateral to epileptogenic side of the brain and the entire limbic system, fit these data with an area under the receiver operating characteristic curve (AUC) of 0.83 and an accuracy of 78%.
These findings may have been biased by the large diversity of TLE seizure features in this patient population.
Ultimately, study data indicated NBM connectivity was altered among patients with TLE and may be a key network for the pathology of this disease.
González HFJ, Narasimhan S, Johnson GW, et al. Role of the nucleus basalis as a key network node in temporal lobe epilepsy. Neurology. 2021;96(9):e1334-e1346. doi:10.1212/WNL.0000000000011523