Using broader term may result in loss of narrower terms

The other day I came across the MeSH term: Trauma, Nervous System. Looking at the MeSH tree, I saw that this term fell under two broader terms:

• Nervous System Diseases
• Wounds and Injuries

However, when I looked at the narrower terms, I discovered that in the tree where Trauma, Nervous System fell under Nervous System Diseases, it had a narrower term, Spinal Cord Injuries, which was not listed in the tree where Trauma, Nervous System fell under Wounds and Injuries.

Here's a picture that hopefully will explain it better:

Note that Spinal Cord Injuries is listed on the left but not the right.

I wondered, if I searched Wounds and Injuries (autoexploded in PubMed), would it search Spinal Cord Injuries, or not?

I tried a search for "Spinal Cord Injuries"[Mesh] NOT "Wounds and Injuries"[Mesh], and there were 73 results. These results had one MeSH term in common: "Autonomic Dysreflexia"[Mesh]

Checking the MeSH tree for Spinal Cord Injuries shows that Autonomic Dysreflexia is a narrower term of Spinal Cord Injuries only when Spinal Cord Injuries is a narrower term of Nervous System Diseases, not Wounds and Injuries.

This means that if a searcher decides to use a MeSH's broader term to search, they risk losing some of the narrower terms of the original MeSH. I didn't know this before, but will be sure to check the tree for this phenomenon in future searches.

BTW, if you're thinking of trying it yourself, you'll notice that Spinal Cord Injuries is also listed immediately under Wounds and Injuries in the tree, which fooled me for a little while. However, this does not change the phenomenon explained above.