Case Notes
History
81 year old female presenting with acute onset mental status change, dizziness, nausea, and gait imbalance.Exam
CTA of the Head
This part of the stroke protocol CTA is performed after the 1st bolus of contrast and is referred to as the initial post contrast head CTA exam. Since there is no recirculation of contrast, it has the advantage of identifying stenoses and short segment occlusions without obscuration by pial collateral. On the other hand, it may underfilling patent, more distal, arteries, which, of course, also reduces the CT-density in the venocapillary pool within brain parenchyma. Thus, the initial post contrast head CTA tends to overestimate the depth of injury in the apparent stroke-zone.
Purpose
1. To define sites of afferent supratentorial arterial thrombosis or flow-limiting high-grade stenosis or lesser but tandem stenoses, or stenosis plus incomplete circle of Willis with isolated arterial circuit;
2. To define sites of afferent infratentorial arterial thrombosis or flow-limiting high-grade stenosis;
3. To determine features of vessel wall and intimal status;
4. To assess presence of tandem stenosis or stenosis plus incompetent circle of Willis;
5. In case of ICA stenosis/occlusion is there effective EC-IC collateral;
6. Is there a watershed stroke zone affecting the usual anastomotic arterial boundary zones;
7. in case of afferent arterial block, plus an incomplete circle of Willis, is there a potential end-of the-line type of watershed stroke;
8. To assess status of retrograde pial collateral and asses for any pial collateral gap between proximal thrombus & retrograde pial collateral;
9. To assess for delayed venous egress (need to prove on post contrast CT head whether it is just delayed or is actually persistently reduced or absent).
This part of the stroke protocol CTA is performed after the 1st bolus of contrast and is referred to as the initial post contrast head CTA exam. Since there is no recirculation of contrast, it has the advantage of identifying stenoses and short segment occlusions without obscuration by pial collateral. On the other hand, it may underfilling patent, more distal, arteries, which, of course, also reduces the CT-density in the venocapillary pool within brain parenchyma. Thus, the initial post contrast head CTA tends to overestimate the depth of injury in the apparent stroke-zone.
Purpose
1. To define sites of afferent supratentorial arterial thrombosis or flow-limiting high-grade stenosis or lesser but tandem stenoses, or stenosis plus incomplete circle of Willis with isolated arterial circuit;
2. To define sites of afferent infratentorial arterial thrombosis or flow-limiting high-grade stenosis;
3. To determine features of vessel wall and intimal status;
4. To assess presence of tandem stenosis or stenosis plus incompetent circle of Willis;
5. In case of ICA stenosis/occlusion is there effective EC-IC collateral;
6. Is there a watershed stroke zone affecting the usual anastomotic arterial boundary zones;
7. in case of afferent arterial block, plus an incomplete circle of Willis, is there a potential end-of the-line type of watershed stroke;
8. To assess status of retrograde pial collateral and asses for any pial collateral gap between proximal thrombus & retrograde pial collateral;
9. To assess for delayed venous egress (need to prove on post contrast CT head whether it is just delayed or is actually persistently reduced or absent).
Prior Study
CT Head1. Hyperdense thrombus is evident in the distal basilar artery extending into the left P1 PCA segment.
2. Multiple recent strokes (readily apparent cytogenic edema sites) involving Lt. PICA and both P4 segments of the PCA were evident on noncontrast CT placing these ischemic events outside the hyperacute treatment timeline on the right and within the timeline on the left. There is an evolving older left PICA stroke. There is parenchymal hypdensity in the deep cerebellar watershed zones, which could be recent ischemia or chronic age-related ischemic demyelination. It is likely there has been recent thrombus in the intradural vertebral artery initially occluding the left PICA, which has then undergone clot lysis with distal secondary embolization to downstream arteries.
CT Perfusion
1. Known acute thrombus in distal basilar artery
2. Focal completed stroke is evident in Lt. PICA perfusion area and early stroke in the Lt. mesial occipital P4-PCA perfusion zone. Reperfusion (increased CBV & CBF) is evident in the Lt. occipital Ischemic zone.
CTA Neck
1. Focal left vertebral artery stenosis without intraluminal soft clot; estimated stenosis is 50% by NASCET & physiologic criteria. This stenosis could be related to an atherosclerotic plaque or from recanalization of a recent thrombus.
2. Occluded distal mesial cerebellar hemispheric branches off the Lt. PICA. The left PICA origin is present but reduced in size consistent with recanalization of a prior thrombus.