Lateral corticospinal tract and termination?

Question

I'm studying the motor pathways of the brain and I'm a bit confused about how the lateral corticospinal tract descends. From `Neuroanatomy: Text and Atlas` by Martin, J. H., 4th edition, right before Figure 10-4: > Some of these [terminating] axons descend ipsilaterally; many descend > contra-laterally and re-cross midline within the gray matter in lamina 10. > The function of these ipsilateral axons is not well understood. I understand that the axons cross over at the Pyramidal decussation, but this paragraph is really confusing me. What descent is being referenced here? Is it descending in the spinal chord? Alternatively, is the paragraph implying that some axons don't decussate in the pyramidal decussation?

Answer 1

You are correct in your last sentence - some axons do not decusssate int eh pyramidal decussation.

Approximately 75 - 90% of the corticospinal fibers in the pyramid cross the median plane in the pyramidal decussation. The rest of the fibers continue uncrossed and remain ipsilateral as the ventral corticospinal tract.