On an axial MRI at the level of the midbrain-pons junction, the structure appearing as a butterfly-shaped high T2 signal in the ventral tegmentum that is abnormal in multiple sclerosis is:
- A Medial longitudinal fasciculus (MLF) ✓
- B Medial lemniscus
- C Corticospinal tract
- D Lateral lemniscus
Correct answer: A. Medial longitudinal fasciculus (MLF)
Explanation
The MLF runs as a paired tract in the dorsal tegmentum of the pons and midbrain, flanking the midline. On axial MRI it appears as a bilateral butterfly or chevron-shaped structure; demyelinating plaques here produce INO. The medial lemniscus is located more ventrally in the tegmentum and carries somatosensory fibres. The corticospinal tract travels through the basis pontis, not the tegmentum. The lateral lemniscus is a dorsolateral structure carrying auditory fibres.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.