A patient has pure hemisensory loss on the right side (face, arm, and leg equally) for all modalities without motor deficits. The most likely lesion site is:

• A Left posterior limb of internal capsule
• B Left primary somatosensory cortex (S1)
• C Left medial lemniscus in the midbrain
• D Left ventral posterolateral (VPL) and ventral posteromedial (VPM) thalamic nuclei ✓

Explanation

A pure hemisensory syndrome affecting face, arm, and leg equally for all modalities (touch, pain, proprioception) with no motor deficit classically localises to a small lacunar infarct of the contralateral VPL (body) and VPM (face) thalamic nuclei, as their compact somatotopy means both are simultaneously affected. A posterior limb internal capsule lesion would tend to include motor fibres. S1 lesions often spare deep sensation disproportionately. Midbrain medial lemniscal lesions spare the face because the trigemino-thalamic fibres travel separately.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.