At which anatomical site do the majority of corticospinal tract fibers cross to the opposite side?
- A Caudal medulla, pyramidal decussation ✓
- B Midbrain, cerebral peduncle
- C Pons, basis pontis
- D Internal capsule, posterior limb
Correct answer: A. Caudal medulla, pyramidal decussation
Explanation
About 75 to 90 percent of corticospinal fibers cross at the pyramidal decussation in the caudal medulla and continue as the lateral corticospinal tract. About 10 percent continue uncrossed as the anterior corticospinal tract and cross segmentally in the cord. The internal capsule and cerebral peduncle carry uncrossed fibers, so lesions there produce contralateral weakness below the face, but they are not crossing points.
Reference: Gray's Anatomy for Students, 4th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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