Stroke diagnostic pathway and patient selection A neurological examination is performed on all patients with suspected hyperacute stroke . National Institutes of Health Stroke Scale ( NIHSS ) score is performed at the time of admission by the stroke team . Patients presenting with NIHSS ≥6 and within six hours of symptom onset for anterior circulation stroke or 12 hours for posterior circulation strokes are considered for mechanical thrombectomy .
As per the NCCCC guidelines , 9 plain CT of the brain is performed immediately to exclude patients with contraindications to treatment , such as acute haemorrhage or significant established ischaemia . For middle cerebral artery territory symptoms , the Alberta Stroke Program Early CT Score ( ASPECTS ) is performed to assess the degree of established ischaemia . Patients with a lack of extensive early ischaemic change ( those with ASPECTS more than 5 on plain CT ) are selected . 8
If there are no contraindications to treatment , then a CT angiogram is performed from aortic arch to the vertex . This helps to delineate the vascular anatomy and assess the patency of the intracranial arterial system , as well as the degree of collateral supply . In patients with uncertain time of symptom onset , brain perfusion imaging ( CT or MRI ) may be employed . 8 The decision to proceed with mechanical thrombectomy is made in conjunction with a stroke physician considering the patient ’ s clinical condition , age and co-morbidities .
Neuro-interventional pathway Once the decision is made to proceed with mechanical thrombectomy , patients are consented and taken to interventional theatre . Intravenous tissue plasminogen activator ( TPA ) is given as a bridging therapy , which is then followed by intra-arterial thrombolysis and mechanical thrombectomy . MT is performed under general anaesthesia or conscious sedation . In our institution , we use a Philips Allura Xper FD20 / 20 biplane X-ray system for image guidance , as it enables FAST acquisition and 3D planning of the Circle of Willis .
Arterial access is gained by using Seldinger catheterisation of the right common femoral artery . A target vessel diagnostic angiography is performed to localise the level of occlusion .
The main two basic thrombectomy techniques involve the use of suction with a pump and / or a stentriever as described below . 1 Suction is performed using a large bore ( 5F or 6F ) catheter , which is engaged with the thrombus and suction is applied either directly with a syringe or a suction pump . 2 A stentriever is a retrievable stent , which is deployed across the thrombus and then pulled back to remove the thrombus . The most common stentrievers used are the Solitaire™ FR Revascularization Device ( Covidien , ev3 Neurovascular , USA ) and the Trevo Pro ( Stryker Neurovascular , Kalamazoo , MI ).
The precise mechanical thrombectomy technique is tailored for each patient based on the following factors : 1 Vascular tortuosity of the aortic arch , internal
Figure 1
Summary of mechanical thrombectomy techniques
scenario No
No vessel tortuosity , short segment occlusion in MCA or PCA
No
Long segment occlusion
No
Tortuous ICA / VBA No
Steep angled MCA occlusion
No
Tandem occlusion No
Anchored thrombus causing ball-valve effect
No
Proximal ICA or BA occlusion
No
Adherent thrombus in terminal ICA or MCA
No
Re-occlusion following thrombectomy
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes technique
Basic stentrieve technique
Ballon guide suction
Distal access catheter +/ - tri-axial system
Proximal stenting and mechanical thrombectomy
Distal access catheter with suction
Plain suction thrombectomy
Intracranial balloon angioplasty and suction thrombectomy
Intracranial stent
carotid artery ( ICA ) or vertebrobasilar artery ( VBA ) 2 The level of occlusion – This may occur at the internal carotid artery ( ICA ), vertebral artery ( VB ), basilar artery ( BA ), middle cerebral artery ( MCA , 1st segment M1 ) or posterior cerebral artery ( PCA , 1st segment P1 )
Length of the thrombus – This can be measured from the CT angiogram .
Using these criteria , a number of techniques of performing mechanical thrombectomy are described 8 and summarised in Figure 1 .
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