Meynert’s basal nucleus (NBM) is possibly the most disturbed network node in patients with temporal lobe epilepsy (TLE). This emerges from study results of a functional magnetic resonance imaging (fMRI) published in Neurology.
Patients (n = 40) who had undergone epilepsy surgery for unilateral mesial TLE at Vanderbilt University Medical Center were recruited for this study. The resting state fMRI findings were compared between patients and healthy control group participants (n = 40). Patients and participants in the control group were 52.5% women and had a mean age of 38.5 years.
Patients were diagnosed with epilepsy an average of 21.1 (range, 2-50) years prior. They reported 9.1 (range 0-195) focal conscious seizures per month and 6.4 (range 0-48) focal conscious seizures per month. 55.0% had focal to bilateral tonic-clonic seizures in the past. During video electroencephalography, the results were well localized (ictal) in 87.5% and lateralized (interictal) in 65.0%. During positron electron tomography, 77.5% showed mesial temporal hypometabolism.
Compared to control group participants, the patients had decreased connectivity between NBM and broad neocortical regions. The patients also had lower connectivity between the NBM and the whole brain both ipsilaterally (0.65 ± 1.11 versus 2.13 ± 1.43; P = 9’10-6) and contralateral (1.18 ± 1 , 10 versus 1.79 ± 1.25; P = 0.03). Sides, depending on the side of the onset of the seizure. The patients had a reduced connectivity between ipsilateral NBM and the frontoparietal cortex compared to the participants in the control group (0.04 ± 1.66 versus 1.47 ± 2.05; P = 0.004).
Patients with a higher frequency of consciousness-impairing partial seizures had a greater decrease in connectivity between the NBM and the frontoparietal cortex (r, -0.41; P = 0.008) than patients with consciousness-impairing partial seizures (r, -0.13; P = 0.418 ).
In a cluster analysis, 95.5% of the regional communities showed similar patterns between cohorts; However, NBMs grouped in different communities between the participants in the control group and the patients. These changed node strengths correlated with language skills (r, 0.53; P <0.001), attention and concentration (r, 0.39; P = 0.011), cognitive processing (r, 0.35; P = 0.035) and visual memory ( r 0.32; P = 0.039).
In a network analysis, the clustering coefficient of all nodes between patients and controls differed between NBM and both ipsilateral (2.23 ± 0.93 vs 3.46 ± 1.17; P = 3.38’10-6) and contralateral Pages (2.63 ± 0.85 vs 3.32 ± 1.12; P = 0.005).
Overall, these data suggest the best-fit model, which requires important connectivity of NBM ipsilateral to the epileptogenic side of the brain and the entire limbic system, with an accuracy of 78%.
These results may have been biased by the wide variety of TLE seizure characteristics in this patient population.
Ultimately, study data indicated that NBM connectivity was altered in patients with TLE and may be a key network in the pathology of this disease.
González HFJ, Narasimhan S., Johnson GW, et al. Role of the basal nucleus as a key network node in temporal lobe epilepsy. Neurology. 2021; 96 (9): e1334-e1346. doi: 10.1212 / WNL.0000000000011523