A 55 year old man presented to the department of emergency medicine after developing right sided weakness and inability to speak. He has a history of hypertension on ACEI.
Q1: List CT head abnormalities seen in an acute ischemic stroke.
A:
1. Hyperdensity within an intracranial vessel owing to intraluminal thrombus.
2. Parenchymal hypoattenuation owing to cytotoxic oedema. Hypoattenuation on CT is highly specific for irreversible ischemic brain damage.
3. Obscuration of gray white matter contrast and effacement of sulci owing to edema
4. Insular ribbon sign. Hypodensity and swelling of insular cortex. Located between the Sylvian fissure and the basal ganglia, it is supplied by small perforating branches of the MCA.
5. Obscuration of the lentiform nucleus. Also called blurred basal ganglia - early and frequent sign in MCA infarction.
Q2: List the abnormalities you might expect to see in an MRI done in a patient with an acute ischaemic stroke.
Answer:
1. Subtle low signal (hypointense) on T1 - often difficult to see at this stage
2. High signal (hyperintense) on T2 - comparable to hypodensity on CT
3. High intensity on DWI - the most sensitive sequence for stroke imaging. DWI sensitive to restriction of Brownian motion of extracellular water due to imbalance caused by cytotoxic edema.
Reduction in the ADC. DWI is sensitive to the microscopic random motion of the water molecule protons, a value known as the apparent diffusion coefficient (ADC), which is measured and captured by this type of imaging. ADC maps allow us to assess the extent of ischaemic disease. Measuring the ADC allows us to get an idea about the depth of ischemia in the penumbra itself and to obtain data regarding tissue viability.
MRI is commonly used method for assessment of the ischemic core and penumbra. The diffusion weight MRI (DWI) lesion is generally assumed to reflect the ischemic infarct, whereas the PWI perfusion weighted MRI (PWI) which uses gadolinium contrast lesion includes both infarct and penumbra hence the potential for perfusion mismatch.
Q1: List CT head abnormalities seen in an acute ischemic stroke.
A:
1. Hyperdensity within an intracranial vessel owing to intraluminal thrombus.
2. Parenchymal hypoattenuation owing to cytotoxic oedema. Hypoattenuation on CT is highly specific for irreversible ischemic brain damage.
3. Obscuration of gray white matter contrast and effacement of sulci owing to edema
4. Insular ribbon sign. Hypodensity and swelling of insular cortex. Located between the Sylvian fissure and the basal ganglia, it is supplied by small perforating branches of the MCA.
5. Obscuration of the lentiform nucleus. Also called blurred basal ganglia - early and frequent sign in MCA infarction.
Q2: List the abnormalities you might expect to see in an MRI done in a patient with an acute ischaemic stroke.
Answer:
1. Subtle low signal (hypointense) on T1 - often difficult to see at this stage
2. High signal (hyperintense) on T2 - comparable to hypodensity on CT
3. High intensity on DWI - the most sensitive sequence for stroke imaging. DWI sensitive to restriction of Brownian motion of extracellular water due to imbalance caused by cytotoxic edema.
Reduction in the ADC. DWI is sensitive to the microscopic random motion of the water molecule protons, a value known as the apparent diffusion coefficient (ADC), which is measured and captured by this type of imaging. ADC maps allow us to assess the extent of ischaemic disease. Measuring the ADC allows us to get an idea about the depth of ischemia in the penumbra itself and to obtain data regarding tissue viability.
MRI is commonly used method for assessment of the ischemic core and penumbra. The diffusion weight MRI (DWI) lesion is generally assumed to reflect the ischemic infarct, whereas the PWI perfusion weighted MRI (PWI) which uses gadolinium contrast lesion includes both infarct and penumbra hence the potential for perfusion mismatch.
