Page created on June 3, 2021. Last updated on April 4, 2022 at 12:47
Evaluation of acute stroke
As with all acute life-threatening conditions it’s important to assess the stability by ABCDE first. All patients with suspected stroke should be admitted to a stroke unit.
Some patients develop the stroke while sleeping, and only note the symptoms after awakening. This is called a “wake-up stroke”, and for the purposes of treatment we define the onset of the stroke to be the time when the patient was last known to be normal, usually the time they went to bed.
The clinical evaluation of patients with suspected stroke must be rapid and usually takes only a few minutes. This is usually performed with a screening tool like National Institute of Health Stroke Scale (NIHSS), which scores the severity of the stroke based on factors like:
- Level of consciousness
- Ability to perform certain movements, like blinking and squeezing hands
- Presence of visual field defect
- Presence of facial palsy
- Arm drift
- Leg drift
- Heel-shin test
- Sensory loss
- Presence of aphasia
The possibility of stroke mimics must always be considered, including:
- Recrudescence of old stroke from metabolic or infectious stress
- Todd’s paralysis after seizure
- Complex migraine
- Pseudoseizure, conversion disorder
The most important and first diagnostic test is native CT. Ischaemia is usually not visible on native CT in the first 6 hours, but intracranial haemorrhage is visible much earlier. Therefore, the goal of native CT is to rule out haemorrhagic stroke. In a patient with clinical features of stroke and no bleeding on CT, ischaemic stroke is presumed. In some cases, the “hyperdense artery” sign can be seen, which is due to a thrombus in the middle cerebral artery.
ECG and labs are important but should not delay the native CT.
The ASPECTS score can be used to score early ischaemic changes on native CT in ischaemic stroke. A score of 10 is a normal native CT, while a score of 0 means that the entire MCA territory is ischaemic.
Vascular imaging (CTA/MRA) is performed after or during the initial native CT. Its purpose is to learn more about the type of stroke, and how good the collateral blood supply is. Vascular imaging can detect a large artery occlusion, which is an indication for thrombectomy.
Sometime during the first days after a stroke, a carotid ultrasound must be made to look for carotid atherosclerosis, which can be a source of embolism or thrombosis. Severe carotid artery stenosis can lead to TIA/ischaemic stroke and may therefore be an indication for carotid endarterectomy or stenting.
The penumbra is the brain area around the infarcted brain which is potentially still salvageable if revascularization occurs in time. In some cases, perfusion imaging (CT perfusion or MRI with DWI) is performed to examine the penumbra. This can be useful if the size of the penumbra influences the decision of whether to perform thrombectomy or not.
For example, if there is a large artery occlusion, and the 6 hour time window for thrombectomy has passed, we may perform perfusion imaging to evaluate whether the penumbra is large enough that late thrombectomy is still beneficial.
If embolic ischaemic stroke is suspected, cardiac investigation is necessary, and includes echocardiography and Holter ECG. These can detect PFO, paroxysmal AF, endocarditis, etc.
Treatment of acute stroke
IV thrombolysis with an rtPA like alteplase is the best treatment for ischaemic stroke. It’s indicated for everyone with ischaemic stroke in which it can be performed within 4,5 hours of symptom onset, but the sooner it’s initiated, the better. It can only be performed if haemorrhagic stroke has been ruled out by native CT.
There are some contraindications, like:
- Previous intracranial haemorrhage
- Intracranial tumour
- Recent surgery or trauma
- INR > 1,7 or recent treatment with heparin or DOAC
Thrombolysis may “convert” the stroke from ischaemic to haemorrhagic, and it may cause severe bleeds anywhere in the body which are difficult to treat. However, it may also completely reverse the stroke symptoms. As such, it’s difficult but important to select the proper canditates for thrombolysis. Imaging is performed 24 hours after thrombolysis to make sure that haemorrhage conversion did not occur.
In Norway, only approx. 15% of stroke patients receive thrombolytic therapy.
Mechanical thrombectomy is indicated if there’s a large artery occlusion visible on vascular imaging. An intravasal catheter is inserted into the femoral artery and led up to the occluded artery in the brain, where the thrombus is removed.
In large artery strokes, thrombolysis is less effective and so thrombectomy may be used. Thrombectomy must be performed within 6 hours of symptom onset, and if they present within 4,5 hours then it should be combined with thrombolysis for best results. If perfusion imaging show a large penumbra, thrombectomy can be performed up to 24 hours after onset.
300 mg ASA is indicated for all cases of ischaemic stroke, but the timing of it depends on whether thrombolysis is performed. If the patient is treated with thrombolysis, aspirin is given after the 24-hour post-thrombolysis imaging has excluded haemorrhage. If the patient does not receive thrombolysis, aspirin is given immediately upon exclusion of haemorrhagic stroke.
If there is a malignant middle cerebral artery infarction, a decompressive hemicranectomy can be performed. This is lifesaving but has high risk of disability.
Supportive treatment is also important. Blood pressure management, blood glucose management, and fluid replacement are necessary. Systolic blood pressure should be kept between 120 mmHg and 220 mmHg.