Undetected abulic state after anterior communicating artery aneurysm surgery under motor evoked potential (MEP) and somatosensory evoked potential (SEP) monitoring

Intraoperative neurophysiologic monitoring (IONM), including somatosensory evoked potential (SEP), and transcranial electric motor evoked potential (MEP), had been utilized during brain or spine surgery to identify neurologic deficits. But some neurologic deficits, such as abulia, could not be detected through routine IONM. MEP or SEP might not monitor non-motor or sensory lesions during surgery. We experienced a 72-year-old case with an anterior communicating aneurysm who experienced abulia after surgery even though routine IONM was performed. There was no abnormality on IONM during aneurysm clipping surgery, but she turned into an abulic state. This case alerts us to the possibility that monitoring failure could occur despite standard IONM procedures using MEP and SEP.