Investigation of choice in spontaneous Sub arachnoid bleed
**Core Concept**
The investigation of choice in spontaneous subarachnoid hemorrhage (SAH) involves imaging techniques to identify the source of bleeding, typically an aneurysm. **Non-contrast computed tomography (CT)** of the head is crucial in diagnosing SAH due to its sensitivity in detecting acute hemorrhage.
**Why the Correct Answer is Right**
Given the context, the correct answer would likely involve a diagnostic imaging modality. **CT angiography** or **MR angiography** could be considered for identifying the source of the bleed, such as an aneurysm, but the initial step in diagnosis, especially in acute settings, would typically be a **non-contrast CT** to quickly identify the presence of blood in the subarachnoid space.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific details of each option, a general approach would be to consider what is not typically the first line in diagnosing spontaneous SAH.
**Option B:** Similarly, this would be incorrect if it does not align with the standard initial imaging modality used.
**Option C:** And this option as well, if it does not represent the best initial choice for diagnosing SAH.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **non-contrast CT** is highly sensitive for acute subarachnoid hemorrhage, making it the initial imaging modality of choice.
**Correct Answer:** D. Non-contrast CT.