Usefulness of motor-evoked potential monitoring during coil embolization of anterior choroidal artery aneurysms: technical reports

Objectives: To determine whether transcranial motor-evoked potential (TCMEP) monitoring is useful for detecting blood flow insufficiency in the anterior choroidal artery (AChA) and reflects motor function during coil embolization of AChA aneurysms. Methods: We analysed MEP findings in seven patients who underwent coil embolization for AChA aneurysms. Corkscrew electrodes positioned at C3 and C4 were used to deliver supra-maximal stimuli (230-550 V). TCMEPs were recorded from the brachioradialis, abductor pollicis brevis, anterior tibialis, and abductor hallucis muscles during all endovascular surgery procedures. Results: Three of seven patients showed transient decreases in TCMEP amplitudes obtained from the lower extremities after coil insertion into the aneurysms, although digital subtraction angiography (DSA) showed no blood flow insufficiency in the AChAs. In two of these three patients, extraction of the coils resulted in recovery of TCMEP amplitudes. In the other patient, the amplitude recovered gradually during repeated TCMEP recordings. One of the three patients experienced transient hemiparesis and aphasia 3 hours after treatment. No patients experienced permanent morbidity post-operatively. Discussion: Decreases in TCMEP amplitude during endovascular treatment for AChA aneurysms are likely to reflect motor dysfunction due to a subtle blood flow insufficiency in the AChA, not detectable by DSA. TCMEP monitoring is a simple and safe monitoring method during coil embolization of AChA aneurysms.