CT scan shows a suharachnoid haemorrhage following symptoms of sudden headache and paralysis. Next investigation of choice is:
**Core Concept**
In cases of suspected subarachnoid hemorrhage (SAH), a crucial step in management is to identify the underlying cause, particularly an aneurysm or arteriovenous malformation (AVM). The next investigation of choice should aim to visualize the cerebral vasculature and detect any abnormalities that may be contributing to the hemorrhage.
**Why the Correct Answer is Right**
Angiography, specifically digital subtraction angiography (DSA), is the gold standard for visualizing the cerebral vasculature and detecting aneurysms or AVMs. This modality provides high-resolution images of the arteries and can identify even small aneurysms or malformations that may not be visible on CT or MRI. The ability to visualize the vasculature in real-time also allows for the assessment of blood flow and potential emboli.
**Why Each Wrong Option is Incorrect**
* **Option A:** CT scan with contrast is not the next investigation of choice because while it can provide some information about the vasculature, it lacks the resolution and specificity needed to detect small aneurysms or AVMs.
* **Option B:** MRI, including MRI angiography, can be useful in evaluating the brain and vasculature, but it is not the preferred modality for detecting aneurysms or AVMs due to its lower spatial resolution compared to DSA.
* **Option D:** Carotid Doppler ultrasound is primarily used to evaluate carotid artery stenosis and is not suitable for visualizing the cerebral vasculature or detecting aneurysms or AVMs.
**Clinical Pearl / High-Yield Fact**
When evaluating a patient with suspected SAH, it is essential to remember that the next investigation of choice should be angiography, specifically DSA, to identify the underlying cause and guide potential intervention.
**Correct Answer: C. Digital subtraction angiography (DSA).**