Utility of motor-evoked potentials in contemporary open thoracoabdominal aortic repair

Paraplegia remains one of the major complications of contemporary open thoracoabdominal aortic aneurysm (TAAA) repair. Intraoperative motor-evoked potentials (MEPs) act as a surrogate measure for spinal cord homeostasis. The purpose of this study was to evaluate the results of intraoperative neuromonitoring in contemporary TAAA repair and its association with postoperative spinal cord ischemia (SCI).

Patients who underwent open type 2 or 3 TAAA or completion aortic repair using intraoperative neuromonitoring were identified between May 2006 and November 2023. Patient demographics, comorbidities, indication for the procedure, procedural details, and outcomes were recorded. The groups were divided based on type of repair, and univariate statistics were then used to evaluate the association of these metrics vs the type of repair.

Seventy-nine patients underwent open type 2 (N = 41) and 3 (N = 23) TAAA and completion aortic (N = 15; open in 14 and endovascular in 1) repairs by a single surgeon. The cohort was predominantly male (N = 48, 60.8%) with a mean age of 52.5 ± 16.2 years. There was a high incidence of hypertension (N = 53, 67.1%), smoking history (N = 42, 53.1%), and connective tissue disorders (N = 37, 46.8%). Operative indications included dissection-related (N = 50, 63.3%) and degenerative (N = 26, 32.9%) TAAA and dissection-related malperfusion (N = 3, 3.8%). Left heart bypass was often (N = 73, 92.4%) used for distal aortic perfusion, and cerebrospinal fluid drainage (N = 77, 97.5%) was a common adjunct. MEPs were classified as no change (N = 43, 54.4%), reversible change (N = 26, 32.9%), irreversible change (N = 4, 5.1%), and unreliable (N = 6, 7.6%). MEP changes were predominantly bilateral (N = 70, 88.6%) and occurred most often during repair of the abdominal aortic segment (N = 13, 16.5%). The median number of replaced vertebral levels was associated with MEP changes (P = .013). SCI was only observed in repairs greater than 6 replaced vertebral levels with an overall frequency of 17.7%. It was most prevalent in completion aortic repairs (26.7%). Immediate and delayed SCI occurred in 10.1% and 7.6% of patients, respectively; it was most commonly (71.8%) reversible. Permanent paraplegia occurred in four patients (5.1%), with equal immediate and delayed onsets. MEPs demonstrated poor sensitivity (53.9%) and specificity (62.3%) for SCI; however, there was a high negative predictive value (86.4%) in this population. In-hospital mortality occurred in five (6.3%) patients.

No changes in intraoperative MEPs are highly predictive of spinal cord homeostasis. The number of replaced vertebral levels and previous aortic repair should guide intraoperative neuroprotective measures including intercostal reimplantation and should take precedence over intraoperative monitoring, especially when MEP changes occur.