Significance of novel subcortical low intensity score on transient neurological events after revascularization surgery for moyamoya disease

Objectives: Transient neurological events (TNEs) are frequently observed after revascularization surgery for moyamoya disease (MMD). Recently, two signs on fluid-attenuated inversion recovery magnetic resonance images, a cortical hyperintensity belt (CHB) sign possibly reflecting vasogenic edema and a transient subcortical low intensity (SCLI) sign possibly reflecting cytotoxic edema, were reported associated with TNEs. The purpose of this study was to create a SCLI score and to investigate the significance of the score in TNEs. Patients and methods: The authors retrospectively analyzed 18 cerebral hemispheres in 16 consecutive patients with revascularization surgery for MMD. The SCLI sign was defined as a transient SCLI in surgically treated hemispheres, and blindly graded as the SCLI score (0-4) based on the extent. The relationships among SCLI, CHB signs and TNEs were evaluated. Results: Postoperative TNEs, SCLI and CHB signs were detected in 8 (44.4%), 9 (50.0%) and 12 (66.7%) hemispheres, respectively. Patients with SCLI and CHB signs had a significantly higher THE occurrence rate than those without these signs (p = 0.015, and p = 0.013, respectively). Patients with TNEs showed significantly higher SCLI scores than those without TNEs (p = 0.009), while the difference of CHB scores did not reach significance between patients with and without TNEs. For the occurrence of postoperative TNEs, SCLI score with a cut-off value of 1.0 resulted in a specificity of 80.0% and a sensitivity of 87.5%. Conclusion: The novel SCLI score may be useful for diagnosing TNEs after revascularization surgery for MMD, although both vasogenic and cytotoxic edema may be involved in postoperative TNEs.