Multimodal carotid occlusion test for determining risk of infarct before therapeutic internal carotid artery occlusion

Abstract

In patients with head and neck carcinoma and extensive cervical metastasis, the topographic and functional relationship of the tumor to the carotid artery is highly important. In case of suspected carotid infiltration, the possibility of a carotid resection or a prosthetic replacement has to be considered preoperatively. Treatment of cavernous carotid aneurysms may also require sacrificing the internal carotid artery (ICA). An interdisciplinary test occlusion of the ICA was performed to assess cerebral collateral circulation prior to permanent carotid occlusion. Fifty-two patients with cervical tumors (n = 45) or inoperable aneurysms (n = 7) were examined. The endovascular balloon test occlusion (BTO) of the ICA was combined with monitoring of the neurological status, cardiovascular status (EKG, blood pressure), cortical function (EEG), and single photon emission CT (SPECT) imaging of the regional cerebral blood flow (rCBF) with 99mTechnetium-HMPAO. In the last 24 patients, transcranial Doppler sonography (TCD) of the ipsilateral middle cerebral artery (MCA) was added for direct hemodynamic monitoring during BTO. In order to improve the diagnostic value of the test results and to simulate hemodynamic crisis, the cerebrovascular reserve capacity was then evaluated with acetazolamide (Diamox). BTO could be performed without neurological complications or carotid dissection. In eight (15%) patients BTO had to be interrupted previously due to neurological symptoms or a delta-EEG. These patients and patients with highly pathological test results in SPECT imaging (n = 9) or TCD (n = 3) were excluded from permanent carotid occlusion. Ten (19%) patients were definitely occluded without hemodynamic complications, but two patients suffered embolic infarctions, which can not be predicted by this procedure. In two patients with a severe hypoperfusion in SPECT imaging, the ICA had to be ligated under emergency conditions following a carotid rupture. Predictably, a hemodynamic infarction occurred postoperatively in both patients. The multimodal BTO with brain perfusion imaging (HMPAO-SPECT) and quantitative blood flow monitoring (TCD) allows a hemodynamic stroke risk assessment prior to permanent occlusion of the ICA. The procedure is important for planning of the therapeutic strategy and for the preoperative dialogue with the patient. Embolic ischemic complications can not be predicted.