The Effect of Cranial Sutures Should Be Considered in Transcranial Electrical Stimulation.

Background: Computational modeling is used to optimize transcranial electrical stimulation (tES) approaches, and the precision of these models is dependent on their anatomical accuracy. We are unaware of any computational modeling of tES that has included cranial sutures.

Objectives: The aims of the study were to review the literature on the timing of closure of the coronal and squamous sutures, which are situated under electrode placements used in tES; to review the literature regarding differences in skull and suture conductivity and to determine a more accurate conductivity for sutures; and to identify magnetic resonance image (MRI) techniques that could be used to detect cranial sutures.

Methods: A scoping review of medical literature was conducted. We conducted computational modeling of a cranial bone plug using COMSOL Multiphysics finite element software, utilizing methodology and results from a previous study. We assessed use of the "3D Slicer" software to identify sutures in routine T1-weighted MRI scans.

Results: Reports from forensic examinations and computed tomography (CT) scans showed suture closure does not correlate with age. Our computational modeling determined a cranial suture conductivity of 0.32 S/m, which is much higher than for skull (compact skull 0.004 S/m, standard trilayer 0.013 S/m). 3D slicer enabled rapid and precise identification of the anatomy and location of cranial sutures.

Conclusions: Cranial sutures persist throughout the lifespan and have a far higher conductivity than skull bone. Cranial sutures can be localized quickly and precisely using a combination of MRI and readily available modeling software. Sutures should be included in tES computational modeling and electroencephalography source imaging to improve the accuracy of results.