Evaluation of proximal-distal velocity gradient in spastic middle cerebral artery after aneurismal subarachnoid hemorrhage

Introduction

Delayed cerebral ischemia (DCI) worsens neurological outcome in patients with aneurysmal subarachnoid hemorrhage (aSAH). DCI pathogenesis is multifactorial and not completely understood, but vasospasm plays a central role. Transcranial color-coded duplex sonography (TCCDS) is a non-invasive bedside tool to explore cerebral vessels, but specificity is still suboptimal. The aim of this study was to evaluate the proximal-distal gradient of mean cerebral blood flow velocity (CBF-V) in middle cerebral artery (MCA) as a possible indicator of critical vasospasm.

Methods

Consecutive aSAH patients (WFNS 1 to 5, age 18 to 80 years) admitted to NeuroICU between November 2011 and September 2012 were included in this study. TCCDS was used to assess CBF-V in MCA of both sides: we defined TCCDS vasospasm as CBF-V >120 cm/second. Magnetic resonance angiography (MRA, 3D TOF HR) was performed to evaluate vasospasm at early (<3 days) and delayed (7 to 10 days) time points. When patients underwent MRA, in the same clinical conditions, we recorded CBF-V with TCCDS at two levels: at the origin (proximal CBF-V) and at the end (distal CBF-V) of the MCA. Then we calculated the absolute value of proximal-distal CBF-V gradient for MCA of both sides. We defined clinical vasospasm as the appearance of a new neurological deficit confirmed by imaging. The relationships between the absolute value of TCCDS CBF-V gradient and (1) TCCDS vasospasm, (2) MRA vasospasm and (3) clinical vasospasm were explored.

Results

We included 26 consecutive aSAH patients (WFNS 1 to 5, age 57 ± 12 years). The absolute value of MCA CBF-V gradient was higher in: (1) vessels affected by TCCDS vasospasm when compared with vessels not affected (63 cm/second, IR 23 to 85 and 15 cm/second IR 7 to 23 respectively, P < 0.001); (2) vessels affected by MRA vasospasm when compared with vessels not affected (43 cm/second, IR 18 to 78 and 13 cm/second IR 6 to 22, P < 0.001); and (3) in patients who developed clinical vasospasm than in patients who did not (56 cm/second IR 11 to 124 and 16 cm/second IR 8 to 30 respectively, P < 0.01). Considering only the subset of MCAs affected by MRA vasospasm, the CBF-V gradient was higher when clinical vasospasm was also present (75 cm/ second IR 56 to 124 and 23 cm/second IR 17 to 30 respectively, P < 0.05).

Conclusion

Proximal-distal CBF-V gradient of MCA might be a reliable indicator of critical vasospasm but further studies are warranted to define threshold values and specificity in aSAH patients.