The organisation of cortical microcolumns within the sulcal bank, tangentially orientated to the skull, allows their detection with magnetoencephalography since their induced magnetic fields will project beyond the skull surface. The organisation of cortical microcolumns within the sulcal bank, tangentially orientated to the skull, allows their detection with magnetoencephalography since their induced magnetic fields will project beyond the skull surface. Conversely, apical dendrites orientated perpendicularly to the skull, as found at the gyral crown, are better detected by EEG. (From Hansen et al5). Malcolm Proudfoot et al. Pract Neurol doi:10.1136/practneurol-2013-000768 ©2014 by BMJ Publishing Group Ltd