gms | German Medical Science

Objective: Superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass surgery continues to play an important role in the management of complex intracranial aneurysms, moyamoya vasculopathy as well as highly selected cases of symptomatic stenoocclusive disease with exhausted cerebrovascular reserve capacity (CVR). Aside from hemodynamic assessment, e.g. using acetazoleamide-challenged perfusion computed tomography (PCT) for evaluation of CVR, visualization of the STA is required for the appropriate planning of the STA exposure during harvesting. We investigated the potential of our standard preoperative perfusion imaging algorithm using dynamic 4D CT angiography (dCTA) for preoperative visualization of the STA in relation to preoperative CA (CA).

Methods: A prospective cohort of 13 patients with either stenoocclusive vessel disease (n=11) or moyamoya vasculopathy (n=2) underwent acetazolamide-challenged whole-brain PCT and CA according to our standardized preoperative evaluation protocol prior to STA-MCA bypass surgery. DCTA images were extracted from the whole-brain PCT dataset. To analyze the accuracy of dCTA in the visualization of the STA, diameters of the STA including the frontal and/or parietal branches were measured and correlated with diameters measured on CA. For this purpose Pearson correlation coefficients were calculated. Moreover, dCTA studies were independently assessed by two vascular neurosurgeons with respect to accuracy for incision planning. We determined whether dCTA alone without CA was sufficient for a definite judgment.

Results: Mean diameters measured by dCTA vs. CA were 1.9 ± 0.4 mm vs. 2.0 ± 0.4 mm for the proximal STA (measured 2cm perpendicular to the external acoustic meatus (EAM)), 1.1 ± 0.3 vs. 1.2 ± 0.3 for the parietal branch (measured 6-7cm perpendicular to the EAM), and 1.4 ± 0.3 vs. 1.4 ± 0.3 for the frontal branch (measured 7-8cm perpendicular to the EAM). There was a strong correlation for the diameters of the STA (r = 0.92; p<0.01), the frontal (r = 0.96; p<0.01) and parietal branch (r = 0.93; p<0.01) between dCTA and CA. Except for one case, where the parietal branch of the STA was not visible in the dCTA; dCTA imaging was rated sufficient for planning of the STA exposure without an additional diagnostic value for CA.

Conclusion: Our data highlight that dCTA derived from preoperative PCT imaging data is comparable to catheter angioraphy with respect to visualization of the STA in the preoperative assessment of STA-MCA bypass surgery. This strongly suggests that pretreatment imaging studies using CA, in addition to PCT imaging may be unnecessary for mere visualization of the STA, especially in view of the invasiveness, risk of thromboembolic complications, additional contrast administration, or radiation exposure of CA. However, in cases of uncertainty CA should be complemented for further evaluation.