FRCR FRCR Neuroradiology 1 — Questions and Answers
Question 1: Which MRI sequence is most sensitive for detecting acute ischemic stroke within the first few hours of symptom onset?
- T1-weighted imaging
- T2-weighted imaging
- Diffusion-weighted imaging (DWI) (Correct answer)
- FLAIR
Correct answer: Diffusion-weighted imaging (DWI)
DWI detects restricted diffusion due to cytotoxic edema within minutes of ischemic onset, making it the most sensitive early sequence.
Question 2: What is the classic CT finding of subarachnoid hemorrhage (SAH) on a non-contrast scan?
- Hypodense blood filling the basal cisterns
- Hyperdense blood filling the basal cisterns (Correct answer)
- Ring-enhancing lesion in the sylvian fissure
- Hypodense midline shift
Correct answer: Hyperdense blood filling the basal cisterns
Fresh clotted blood is hyperdense (35–90 HU) due to protein in hemoglobin, appearing bright white in the basal cisterns on non-contrast CT.
Question 3: Which arteries are most commonly responsible for hypertensive hemorrhage in the basal ganglia?
- Middle cerebral artery branches
- Posterior inferior cerebellar artery
- Lenticulostriate arteries (Correct answer)
- Anterior choroidal artery
Correct answer: Lenticulostriate arteries
The lenticulostriate arteries are small perforating end-arteries from the MCA that are highly susceptible to hypertensive damage and rupture.
Question 4: The 'empty delta sign' on contrast-enhanced CT is associated with which condition?
- Cerebral abscess
- Superior sagittal sinus thrombosis (Correct answer)
- Acute subdural hematoma
- Epidural hematoma
Correct answer: Superior sagittal sinus thrombosis
Enhancement of the dural walls around a non-enhancing thrombus in the superior sagittal sinus creates a triangular filling defect — the 'empty delta sign'.
Question 5: Which imaging feature best distinguishes a high-grade glioma from a solitary metastasis on MRI?
- Presence of ring enhancement
- Degree of surrounding vasogenic edema
- Tumor infiltration crossing the corpus callosum (Correct answer)
- Degree of mass effect
Correct answer: Tumor infiltration crossing the corpus callosum
High-grade gliomas can infiltrate along white matter tracts and cross the corpus callosum ('butterfly glioma'), a pattern not seen with metastases.
Question 6: What is the typical MRI appearance of multiple sclerosis (MS) plaques?
- T1 hypointense, T2 hypointense lesions in the gray matter
- T1 isointense, T2/FLAIR hyperintense periventricular white matter lesions (Correct answer)
- T1 hyperintense, T2 hypointense deep white matter lesions
- T1 and T2 hypointense cortical lesions
Correct answer: T1 isointense, T2/FLAIR hyperintense periventricular white matter lesions
MS demyelinating plaques are classically periventricular, ovoid, and T2/FLAIR hyperintense due to increased water content from demyelination and inflammation.
Question 7: A 38-year-old presents with sudden-onset 'thunderclap' headache. Non-contrast CT of the brain is negative. What is the next most appropriate investigation?
- MRI brain with gadolinium
- CT angiography of cerebral vessels
- Lumbar puncture for xanthochromia (Correct answer)
- Electroencephalogram (EEG)
Correct answer: Lumbar puncture for xanthochromia
A negative CT does not exclude SAH, particularly beyond 6 hours; LP to detect xanthochromia remains the gold standard in this scenario.
FRCR FRCR Neuroradiology 1
Which MRI sequence is most sensitive for detecting acute ischemic stroke within the first few hours of symptom onset?