Modification of electrophysiological activity pattern after anterior thalamic deep brain stimulation for intractable epilepsy: report of 3 cases.

OBJECTIVE Thalamic stimulation can provoke electroencephalography (EEG) synchronization or desynchronization, which can help to reduce the occurrence of seizures in intractable epilepsy, though the underlying mechanism is not fully understood. Therefore, the authors investigated changes in EEG electrical activity to better understand the seizure-reducing effects of deep brain stimulation (DBS) in patients with intractable epilepsy. METHODS Electrical activation patterns in the epileptogenic brains of 3 patients were analyzed using classical low-resolution electromagnetic tomography analysis recursively applied (CLARA). Electrical activity recorded during thalamic stimulation was compared with that recorded during the preoperative and postoperative off-stimulation states in patients who underwent anterior thalamic nucleus DBS for intractable epilepsy. RESULTS Interictal EEG was fully synchronized to the β frequency in the postoperative on-stimulation period. The CLARA showed that electrical activity during preoperative and postoperative off-stimulation states was localized in cortical and subcortical areas, including the insular, middle frontal, mesial temporal, and precentral areas. No electrical activity was localized in deep nucleus structures. However, with CLARA, electrical activity in the postoperative on-stimulation period was localized in the anterior cingulate area, basal ganglia, and midbrain. CONCLUSIONS Anterior thalamic stimulation could spread electrical current to the underlying neuronal networks that connect with the thalamus, which functions as a cortical pacemaker. Consequently, the thalamus could modify electrical activity within these neuronal networks and influence cortical EEG activity by inducing neuronal synchronization between the thalamus and cortical structures.

KEYWORDS: ATN = anterior thalamic nucleus; CLARA = classical LORETA analysis recursively applied; DBS = deep brain stimulation; EEG = electroencephalography; GABA = γ-aminobutyric acid; IPG = implantable programmable generator; LORETA = low-resolution electromagnetic tomography; anterior thalamic nucleus; deep brain stimulation; electroencephalography; functional neurosurgery; intractable epilepsy

PMID: 27636181 DOI: 10.3171/2016.6.JNS152958