On an axial MRI of the brain at the level of the basal ganglia, the structure that appears as a biconvex (lens-shaped) region of grey matter lateral to the internal capsule with a darker centre (globus pallidus) on T2-weighted imaging is:
- A Lentiform nucleus (putamen + globus pallidus) ✓
- B Caudate nucleus
- C Thalamus
- D Claustrum
Correct answer: A. Lentiform nucleus (putamen + globus pallidus)
Explanation
The lentiform nucleus (wedge-shaped on axial section, lens-shaped on coronal) lies lateral to the internal capsule and medial to the external capsule. On T2 MRI the globus pallidus appears darker than the putamen due to iron deposition, creating a distinctive two-tone appearance. The caudate nucleus lies medial to the internal capsule forming the lateral wall of the lateral ventricle. The thalamus lies medial and posterior. The claustrum is a thin sliver of grey matter between external and extreme capsules.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.