Which spinal levels are involved if a tetraplegic horse can't raise its head?

Which spinal levels are involved if a tetraplegic horse can't raise its head?

• A. C4-C6
• B. T2-T5
• C. C7-T1
• D. C1-C3

Answer: (D)

Raising the head is controlled by neck muscles that receive motor input from the upper cervical spinal cord. If a horse is tetraplegic and can’t lift its head, the injury is at the very top of the cervical region, where the neurons that drive those neck muscles reside. Specifically, the neurons that power neck extension and head elevation come from the first cervical segments, so damage from C1 through C3 would abolish the ability to raise the head. Lower cervical injuries (such as C4-C6 or C7-T1) or thoracic injuries would not eliminate all neck muscle control to the extent needed to keep the head from rising, because those levels don’t govern those key neck-extensor muscles. So, involvement of the upper cervical segments, C1-C3, best explains the described deficit.

Raising the head is controlled by neck muscles that receive motor input from the upper cervical spinal cord. If a horse is tetraplegic and can’t lift its head, the injury is at the very top of the cervical region, where the neurons that drive those neck muscles reside. Specifically, the neurons that power neck extension and head elevation come from the first cervical segments, so damage from C1 through C3 would abolish the ability to raise the head. Lower cervical injuries (such as C4-C6 or C7-T1) or thoracic injuries would not eliminate all neck muscle control to the extent needed to keep the head from rising, because those levels don’t govern those key neck-extensor muscles. So, involvement of the upper cervical segments, C1-C3, best explains the described deficit.