Orbitofrontal epilepsy: Electroclinical analysis of surgical cases and literature review

Clinical and electrographic data were reviewed on 2 of our patients with orbitofrontal epilepsy who were seizure free at 5-year follow-up, and on 2 similar patients from the literature. One of our patients was lesional, and the other was nonlesional. Interictal EEG discharges were lateralized to the side of invasively recorded orbitofrontal seizures in the nonlesional case. In this case, no clinical manifestations occurred until the orbitofrontal discharge had spread to the opposite orbitofrontal and both mesial temporal areas. Unresponsiveness or arrest of activity were the initial manifestations of complex partial seizures in both cases. The 2 cases from the literature with long-term seizure-free follow-up had little impairment of awareness and displayed vigorous motor automatisms. Interictal epileptiform activity was bifrontally synchronous in 1 case. Ipsilateral frontotemporal discharges were seen in both. Invasive ictal epileptiform activity appeared maximal in the ipsilateral orbitofrontal region in both patients. No consistent electrographic or clinical pattern characterized these 4 cases. Seizures of orbitofrontal origin may be characterized by either unresponsiveness associated with oroalimentary automatisms or limited alteration of awareness and associated with vigorous motor automatisms. Invasive monitoring of the orbitofrontal cortex should be considered in nonlesional cases with complex partial seizures that show nonlocalizing ictal patterns and interictal frontal or frontotemporal epileptiform discharges. Copyright (C) 2004 S. Karger AG, Basel

Differential modulation of excitatory and inhibitory neurons during periodic stimulation

Non-invasive transcranial neuronal stimulation, in addition to deep brain stimulation, is seen as a promising therapeutic and diagnostic approach for an increasing number of neurological diseases such as epilepsy, cluster headaches, depression, specific type of blindness, and other central nervous system disfunctions. Improving its effectiveness and widening its range of use may strongly rely on development of proper stimulation protocols that are tailored to specific brain circuits and that are based on a deep knowledge of different neuron types response to stimulation. To this aim, we have performed a simulation study on the behavior of excitatory and inhibitory neurons subject to sinusoidal stimulation. Due to the intrinsic difference in membrane conductance properties of excitatory and inhibitory neurons, we show that their firing is differentially modulated by the wave parameters. We analyzed the behavior of the two neuronal types for a broad range of stimulus frequency and amplitude and demonstrated that, within a small-world network prototype, parameters tuning allow for a selective enhancement or suppression of the excitation/inhibition ratio

Deep brain stimulator implantation in a diagnostic MRI suite: infection history over a 10-year period

OBJECTIVE The objective of this study was to assess the incidence of postoperative hardware infection following interventional (i)MRI-guided implantation of deep brain stimulation (DBS) electrodes in a diagnostic MRI scanner. METHODS A diagnostic 1.5-T MRI scanner was used over a 10-year period to implant DBS electrodes for movement disorders. The MRI suite did not meet operating room standards with respect to airflow and air filtration but was prepared and used with conventional sterile procedures by an experienced surgical team. Deep brain stimulation leads were implanted while the patient was in the magnet, and patients returned 1-3 weeks later to undergo placement of the implantable pulse generator (IPG) and extender wire in a conventional operating room. Surgical site infections requiring the removal of part or all of the DBS system within 6 months of implantation were scored as postoperative hardware infections in a prospective database. RESULTS During the 10-year study period, the authors performed 164 iMRI-guided surgical procedures in which 272 electrodes were implanted. Patients ranged in age from 7 to 78 years, and an overall infection rate of 3.6% was found. Bacterial cultures indicated Staphylococcus epidermis (3 cases), methicillin-susceptible Staphylococcus aureus (2 cases), or Propionibacterium sp. (1 case). A change in sterile practice occurred after the first 10 patients, leading to a reduction in the infection rate to 2.6% (4 cases in 154 procedures) over the remainder of the procedures. Of the 4 infections in this patient subset, all occurred at the IPG site. CONCLUSIONS Interventional MRI-guided DBS implantation can be performed in a diagnostic MRI suite with an infection risk comparable to that reported for traditional surgical placement techniques provided that sterile procedures, similar to those used in a regular operating room, are practiced