Novel Intraoperative Neurophysiologic Monitoring (IONM) Techniques during Thoracic Endovascular Aortic Repair (TEVAR) to Rapidly Assess Central Spinal Cord versus Peripheral Limb Ischemia

OBJECTIVE: present a novel multimodality IONM approach to facilitate rapid assessment and prompt differentiation of contributing factors to suspected ischemia during BACKGROUND: utility of IONM, including somatosensory evoked potentials (SSEPs) and/or transcranial motor evoked potentials (tcMEPs) during TEVAR has previously been described, but there remains no consensus regarding standardized neuromonitoring protocols. Traditional SSEPs and tcMEPs alone may not adequately distinguish central spinal cord versus peripheral limb ischemia, which is of critical importance. METHODS: present five TEVAR cases for which a unique multimodality IONM protocol was employed that incorporates pudendal/perianal SSEPs and anal sphincter tcMEPs, along with upper/lower extremity SSEPs and tcMEPs, as well as electroencephalography (EEG). RESULTS: all five cases reliable bilateral anal sphincter tcMEPs were obtained, and in two cases reproducible pudendal/perianal SSEPs were also elicited. In two cases, sudden loss of leg SSEPs and/or tcMEPs was observed during selective vessel catheterization. In contrast, anal sphincter tcMEPs and pudendal/perianal SSEPs remained unchanged. This pattern appeared consistent with transient peripheral limb ischemia rather than spinal cord ischemia (SCI). Following stent deployment, leg SSEPs and tcMEPs returned to baseline with no further changes. In all cases bilateral anal sphincter tcMEPs remained stable throughout TEVAR. All patients awoke postoperatively with no new neurologic deficits or symptoms to suggest recent or delayed onset CONCLUSIONS: Spinal cord and limb ischemia are potential complications of TEVAR. The loss of extremity SSEPs/tcMEPs with preservation of pudendal/perianal SSEPs and anal sphincter tcMEPs suggests peripheral limb ischemia rather than SCI. We advocate the routine monitoring of anal sphincter tcMEPs and pudendal/perianal SSEPs in conjunction with traditional IONM techniques, to allow for rapid differentiation between central and peripheral causes of evolving ischemia. The surgeon may then better ascertain the need for more aggressive versus conservative treatment interventions to improve perioperative outcomes. Disclosure: Dr. Lee has nothing to disclose. Dr. Lee has nothing to disclose. Dr. Jones has nothing to disclose. Dr. Cho has nothing to disclose. Dr. Nguyen has nothing to disclose. Dr. Le has nothing to disclose. Dr. Lopez has received research support from Earlogic/Good Ear Company.