Question

In imaging a case of acute ischemic stroke, discuss:
Imaging findings on CT head.

Hint:

In acute ischemic stroke, CT is useful for detecting hemorrhage and early signs of ischemia, but it may not reveal ischemic changes until several hours after the onset. A follow-up CT or MRI may be needed for definitive assessment.

Answer 1

Step 1: Understanding Acute Ischemic Stroke.
Acute ischemic stroke occurs when blood flow to a region of the brain is interrupted, leading to neuronal injury and infarction. The primary goal of imaging is to confirm the diagnosis, assess the extent of damage, and rule out other causes of neurological deficits such as hemorrhage. CT imaging is often the first modality used in suspected stroke cases.

Step 2: CT Imaging Findings in Acute Ischemic Stroke.
1. Early CT Findings (0-6 hours):
- Normal CT: In the early stages of ischemic stroke, CT may appear normal. This is because changes due to ischemia may not be visible immediately on CT scans.
- Hypodensity: As ischemia progresses, the affected brain region may show hypodensity (darker areas), which indicates tissue infarction. This is usually not evident until 6-24 hours after the onset of symptoms.
- Loss of gray-white matter differentiation: This is one of the first changes seen in acute ischemia, where the normal distinction between the gray matter and white matter becomes blurred due to cytotoxic edema.

2. Intermediate CT Findings (24-48 hours):
- Well-defined Hypodense Area: The infarcted area becomes more clearly visible as it becomes hypodense (darker) compared to normal brain tissue.
- Mass Effect: Swelling or edema within the infarcted area can cause a mass effect, leading to midline shift or compression of adjacent structures.

3. Late CT Findings (3-7 days):
- Cystic Changes: In the later stages, infarcted tissue may undergo liquefaction, leading to the formation of cystic areas or an encephalomalacic cavity.
- Atrophy: With chronic infarction, there can be atrophy or shrinkage of the brain tissue in the infarcted area, which is visible on follow-up CT scans.

Step 3: Conclusion.
CT is often the first imaging modality used to rule out hemorrhage and detect early ischemic changes. However, it may not show ischemic changes immediately, and follow-up imaging is important for assessing the full extent of the stroke.