We suggest performing CT perfusion, CT angiography, transcranial Doppler, or a radionuclide brain perfusion study employing a lipophilic radiopharmaceutical (with or without tomographic imaging) in adult patients who require ancillary investigation for DNC (weak recommendation, very low to moderate certainty in evidence). We suggest against performing EEG, BAEP, SSEP, a radionuclide brain flow only study employing a lipophobic radiopharmaceutical, four-vessel cerebral angiography, or magnetic resonance imaging in adult patients who require ancillary investigation for DNC (weak recommendation, very low certainty in evidence).