Question 1: What is the investigation of choice for diagnosing subarachnoid hemorrhage (SAH)?
- A. Radionuclide scan
- B. X-ray skull
- C. MRI
- D. CT scan (Correct Answer)
Explanation: ***CT scan***
- A **non-contrast CT scan of the head** is the immediate investigation of choice for diagnosing SAH due to its high sensitivity for detecting fresh blood.
- It can quickly identify the presence of **blood in the subarachnoid space**, especially within the first 6-12 hours after symptom onset.
*Radionuclide scan*
- This imaging technique uses **radioactive tracers** to evaluate organ function or blood flow.
- It is **not used for acute diagnosis** of SAH, as it does not directly visualize blood in the CNS.
*X-ray skull*
- An **X-ray of the skull** primarily visualizes bone structures and can detect fractures or other bony abnormalities.
- It is **ineffective at detecting blood** in the subarachnoid space and is not used for SAH diagnosis.
*MRI*
- While MRI can detect SAH, especially in subacute or chronic phases, it is **less sensitive than CT for acute SAH** due to longer acquisition times and motion artifacts.
- It is often considered if CT is negative and clinical suspicion remains high, but **not as the initial investigation of choice** in an acute setting.