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Florian Connolly, Stephan J. Schreiber, Christoph Leithner, Georg Bohner, Peter Vajkoczy, and José M. Valdueza

OBJECTIVE

Transcranial color-coded duplex sonography (TCCS) is a reliable tool that is used to assess vasospasm in the M1 segment of the middle cerebral artery (MCA) after subarachnoid hemorrhage (SAH). A distinct increase in blood flow velocity (BFV) is the principal criterion for vasospasm. The MCA/internal carotid artery (ICA) index (Lindegaard Index) is also widely used to distinguish between vasospasm and cerebral hyperperfusion. However, extracranial ultrasonography assessment of the neck vessels might be difficult in an intensive care unit. Therefore, the authors evaluated whether the relationship of intracranial arterial to venous BFV might indicate vasospasm with similar or even better accuracy.

METHODS

Patients who presented between 2008 and 2015 with aneurysmal SAH were prospectively enrolled in the study. Digital subtraction angiography (DSA) and TCCS were performed within 24 hours of each other to assess vasospasm 8–10 days after SAH. The following different TCCS parameters were analyzed to assess vasospasm in the MCA and were compared with the gold-standard DSA parameters: 1) mean time-averaged maximum BFV (Vmean) of the MCA, 2) peak systolic velocity (PSV) of the MCA, 3) the Lindegaard Index using Vmean as well as PSV, and 4) a new arteriovenous index (AVI) between the MCA and the basal vein of Rosenthal using Vmean and PSV. The best cutoff values for these parameters to distinguish vasospasm from normal perfusion or hyperperfusion were calculated using receiver operating characteristic curve analysis. Sensitivity, specificity, positive predictive value, and negative predictive value as well as the overall accuracy for each cutoff value were analyzed.

RESULTS

A total of 102 patients (mean age 52 ± 12 years) were evaluated. Bilateral MCA assessment by TCCS was successful in all patients. In 6 cases (3%), the BFV of the basal vein of Rosenthal could not be analyzed. The AVI could not be calculated in 50 of 204 cases (25%) because the insonation quality was very low in one of the ICAs. An AVI > 10 for Vmean and an AVI > 12 for systolic velocity provided the highest accuracies of 87% and 86%, respectively. Regarding the Lindegaard Index, the accuracy was highest using a threshold of > 3 for the mean BFV (84%) as well as systolic BFV (80%). BFVs in the MCA of ≥ 120 cm/sec (Vmean) and ≥ 200 cm/sec (PSV) predicted vasospasm with accuracies of 84% and 83%, respectively. A combined analysis of the MCA BFV and the AVI led to a slight increase in specificity (Vmean, 94%; PSV, 93%) and positive predictive value (Vmean, 88%; PSV 86%) without further improvement in accuracy (Vmean, 88%; PSV, 84%).

CONCLUSIONS

The intracranial AVI is a reliable parameter that can be used to assess vasospasm after SAH. Its reliability for differentiating vasospasm and hyperperfusion is slightly higher than that for the established Lindegaard Index, and this method has the additional advantage of a remarkably lower failure rate.

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Florian Connolly, Joan Alsolivany, Marcus Czabanka, Peter Vajkoczy, Jose M. Valdueza, Jens E. Röhl, Eberhard Siebert, and Leon A. Danyel

OBJECTIVE

Superficial temporal artery–middle cerebral artery (STA-MCA) bypass surgery is an important therapy for symptomatic moyamoya disease. Its success depends on bypass function, which may be impaired by primary or secondary bypass insufficiency. Catheter angiography is the current gold standard to assess bypass function, whereas the diagnostic value of ultrasonography (US) has not been systematically analyzed so far.

METHODS

The authors analyzed 50 STA-MCA bypasses in 39 patients (age 45 ± 14 years [mean ± SD]; 26 female, 13 male). Bypass patency was evaluated by catheter angiography, which was performed within 24 hours after US. The collateral circulation through the bypass was classified into 4 types as follows: the bypass supplies more than two-thirds (type A); between one-third and two-thirds (type B); or less than one-third (type C) of the MCA territory; or there is bypass occlusion (type D). The authors assessed the mean blood flow velocity (BFV), the blood volume flow (BVF), and the pulsatility index (PI) in the external carotid artery and STA by duplex sonography. Additionally, they analyzed the flow direction of the MCA by transcranial color-coded sonography. US findings were compared between bypasses with higher (types A and B) and lower (types C and D) capacity.

RESULTS

Catheter angiography revealed high STA-MCA bypass capacity in 35 cases (type A: n = 22, type B: n = 13), whereas low bypass capacity was noted in the remaining 15 cases (type C: n = 12, type D: n = 3). The BVF values in the STA were 60 ± 28 ml/min (range 4–121 ml/min) in the former and 12 ± 4 ml/min (range 6–18 ml/min) in the latter group (p < 0.0001). Corresponding values of mean BFV and PI were 57 ± 21 cm/sec (range 16–100 cm/sec) versus 22 ± 8 cm/sec (range 10–38 cm/sec) (p < 0.0001) and 0.8 ± 0.2 (range 0.4–1.3) versus 1.4 ± 0.5 (range 0.5–2.4) (p < 0.0001), respectively. Differences in the external carotid artery were less distinct: BVF 217 ± 71 ml/min (range 110–425 ml/min) versus 151 ± 41 ml/min (range 87–229 ml/min) (p = 0.001); mean BFV 47 ± 17 cm/sec (range 24–108 cm/sec) versus 40 ± 7 cm/sec (range 26–50 cm/sec) (p = 0.15); PI 1.5 ± 0.4 (range 1.0–2.5) versus 1.9 ± 0.4 (range 1.2–2.6) (p = 0.009). A retrograde blood flow in the MCA was found in 14 cases (9 in the M1 and M2 segment; 5 in the M2 segment alone), and all of them showed a good bypass function (type A, n = 10; type B, n = 4). The best parameter (cutoff value) to distinguish bypasses with higher capacity from bypasses with lower capacity was a BVF in the STA ≥ 21 ml/min (sensitivity 100%, negative predictive value 100%, specificity 91%, positive predictive value 83%).

CONCLUSIONS

Duplex sonography is a suitable diagnostic tool to assess STA-MCA bypass function in moyamoya disease. Hemodynamic monitoring of the STA by US provides an excellent predictor of bypass patency.