Tomohiro Kawaguchi, Shinjitsu Nishimura, Masayuki Kanamori, Hiroki Takazawa, Shunsuke Omodaka, Kenya Sato, Noriko Maeda, Yoko Yokoyama, Hiroshi Midorikawa, Tatsuya Sasaki and Michiharu Nishijima
The difference in the hemodynamics of wall shear stress (WSS) and oscillatory shear index (OSI) between ruptured and unruptured aneurysms is not well understood. The authors investigated the hemodynamic similarities and dissimilarities in ruptured and thin-walled unruptured aneurysm blebs.
Magnetic resonance imaging–based fluid dynamics analysis was used to calculate WSS and OSI, and hemodynamic and intraoperative findings were compared. The authors also compared ruptured and unruptured thin-walled blebs for the magnitude of WSS and OSI.
Intraoperatively, 13 ruptured and 139 thin-walled unruptured aneurysm blebs were identified. Twelve of the ruptured (92.3%) and 124 of the unruptured blebs (89.2%) manifested low WSS and high OSI. The degree of WSS was significantly lower in ruptured (0.49 ± 0.12 Pa) than in unruptured (0.64 ± 0.15 Pa; p < 0.01) blebs.
Ruptured and unruptured blebs shared a distinctive pattern of low WSS and high OSI. The degree of WSS at the rupture site was significantly lower than in the unruptured thin-walled blebs.
Sumito Okuyama, Shinjitsu Nishimura, Yoshiharu Takahashi, Keiichi Kubota, Takayuki Hirano, Ken Kazama, Masato Tomii, Junko Matsuyama, Junichi Mizuno, Tadao Matsushima, Masataka Sato and Kazuo Watanabe
Hypoperfusion during carotid artery cross-clamping (CC) for carotid endarterectomy (CEA) may result in the major complication of perioperative stroke. Median nerve somatosensory evoked potential (MNSSEP) monitoring, which is an established method for the prediction of cerebral ischemia, has low sensitivity in detecting such hypoperfusion. In this study the authors sought to explore the limitations of MNSSEP monitoring compared to tibial nerve somatosensory evoked potential (TNSSEP) monitoring for the detection of CC-related hypoperfusion.
The authors retrospectively analyzed data from patients who underwent unilateral CEA with routine shunt use. All patients underwent preoperative magnetic resonance angiography and were monitored for intraoperative cerebral ischemia by using MNSSEP, TNSSEP, and carotid stump pressure during CC. First, the frequency of MNSSEP and TNSSEP changes during CC were analyzed. Subsequently, variables related to stump pressure were determined by using linear analysis and those related to each of the somatosensory evoked potential (SSEP) changes were determined by using logistic regression analysis.
A total of 94 patients (mean age 74 years) were included in the study. TNSSEP identified a greater number of SSEP changes during CC than MNSSEP (20.2% vs 11.7%; p < 0.05). Linear regression analysis demonstrated that hypoplasia of the contralateral proximal segment of the anterior cerebral artery (A1 hypoplasia) (p < 0.01) and hypoplasia of the ipsilateral precommunicating segment of the posterior cerebral artery (P1 hypoplasia) (p = 0.02) independently and negatively correlated with stump pressure. Both contralateral A1 hypoplasia (OR 26.25, 95% CI 4.52–152.51) and ipsilateral P1 hypoplasia (OR 8.75, 95% CI 1.83–41.94) were independently related to the TNSSEP changes. However, only ipsilateral P1 hypoplasia (OR 8.76, 95% CI 1.61–47.67) was independently related to MNSSEP changes.
TNSSEP monitoring appears to be superior to MNSSEP in detecting CC-related hypoperfusion. Correlation with stump pressure and SSEP changes indicates that TNSSEP, and not MNSSEP monitoring, is a reliable indicator of cerebral ischemia in the territory of the anterior cerebral artery.