Authors :
Presenting Author: Shalini Narayana, PhD – University of Tennessee Health Science Center, Le Bonheur Children's Hospital, Memphis TN
First Author: Jackie Verner, MS –
Roozbeh Rezaie, PhD – Associate Professor, Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, TN, USA; Neuroscience Institute, Le Bonheur Children’s Hospital, Memphis, TN, USA;; Negar Noorizadeh, PhD – Instructor, Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, TN, USA; Neuroscience Institute, Le Bonheur Children’s Hospital, Memphis, TN, USA;; Frederick A. Boop, MD – Professor, Department of Neurosurgery, University of Tennessee Health Science Center;; Stephen P. Fulton, MD – Associate Professor, Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, TN, USA; Neuroscience Institute, Le Bonheur Children’s Hospital, Memphis, TN, USA;; Paul Klimo, MD – Professor, Department of Neurosurgery, University of Tennessee Health Science Center; Neuroscience Institute, Le Bonheur Children’s Hospital, Memphis, TN, USA;; James W. Wheless, MD – Professor, Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, TN, USA; Neuroscience Institute, Le Bonheur Children’s Hospital, Memphis, TN, USA;; Shalini Narayana, PhD – Professor, Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, TN, USA; Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA; Neuroscience Institute, Le Bonheur Children’s Hospital, Memphis, TN, USA
Rationale:
Responsive neurostimulation (RNS) is a treatment option for patients with refractory epilepsy who may not be candidates for surgical resection due to overlap of the ictal onset zone with eloquent cortex. Accurate localization of the ictal onset zone and eloquent cortex has traditionally been done by using intracranial electrodes. We investigated whether non-invasive methods such as transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG) may also achieve this goal sufficiently. This study evaluated the success rates of TMS in eloquent cortex mapping and MEG in ictal onset localization and eloquent cortex mapping.
Methods:
A retrospective chart review to identify patients who had received RNS placement was conducted to determine if non-invasive methods of ictal onset localization and eloquent cortex mapping aided in presurgical evaluation and precise placement of RNS. Surgical evaluation procedures were reviewed including electrocorticography (ECoG), TMS, and MEG. The type of procedure for each patient was recorded as well as the successful completion of the procedure. Additionally, the number of neurosurgical procedures prior to RNS was noted. The critical evaluated outcome was the successful completion of non-invasive procedures for determining seizure focus by MEG and eloquent cortex mapping by TMS and MEG.
Results:
Eight patients who underwent RNS placement were identified. The sample had a mean age of 21.8 (SD = 4.2) and 62.5% were female. Of those patients, three and five were determined to have seizure foci in speech areas and motor areas, respectively. For seven of eight patients, characterization of the irritative zone using MEG was successful. Electrocorticography for the purpose of identifying ictal onset zone was performed in three of eight patients and successful in all three. Seven patients underwent relevant eloquent cortex mapping by TMS (successful in seven of eight patients), and five of eight patients underwent relevant eloquent cortex mapping by MEG (successful in two of five patients). See Table 1 for sample details.
Conclusions:
RNS placement is ideal for patients with a seizure focus in eloquent cortex. Accurate and precise identification of both is pertinent. These data demonstrated that TMS and MEG may be feasible alternatives to invasive monitoring methods for identifying seizure foci and relevant eloquent cortices in the majority of patients who underwent RNS placement. Given that the median number of neurosurgical procedures was three, taking steps to reduce surgery morbidity for patients may lead to better care. Non-invasive methods for determining RNS candidacy have a high rate of success when data from multiple non-invasive modalities converge and may inform more accurate placement of intracranial electrodes prior to RNS placement or eliminate their need.
Funding: N/A