WILTIMS #131: I'm droopy... or have a cranial nerve palsy

I thought we already covered cranial nerves in gross anatomy all those months ago. I was wrong. Oh so wrong. The 2½ hours of lecture this morning exclusively on cranial nerves and their associated spinal cord nuclei taught me that the hours spent in gross anatomy were just a friendly introduction to convoluted roadmap of neurons that control an enormous amount of the head and body from a scattered core of seemingly indistinguishable spinal cord chunks. An we still have several lectures to come on eyesight and the optic nerve (CNII).

This afternoon we had a fantastic lecture on the ethics of procreation and genetic testing by this guy. He managed to quickly and objectively sum up the arguments from everything from abortion to cloning to "designer children." One of the more interesting points was on the future of certain technologies and their impact on the long held ethical beliefs of all parties involved. How does the debate over abortion change one we create the artificial uterus? That's not ridiculous to think about considering how medical science has continued to push back the limits of premature viability and push forward in vitro early embryonic development.

TIL: One of the cranial nerve exams is to have the patient sick out his or her tongue. If it deviates to the right, either the upper motor neuron of the left hypoglossal nerve (CNXII) or the right lower motor neuron has been damaged.

Along the same theme, because the upper portion of the face is innervated by both sides of cranial nerve VII but the lower muscles of facial expression are innervated purely contralaterally (from the opposite side), if you have a left upper motor neuron lesion you will have a droopy lower right face, while a lower motor neuron lesion will result in a Bell's palsy (half face droopiness) in the ipsilateral side.

If one of the abducens nerves (CNVI) is damaged, it will result in double vision that resolves if the patient turns his or her head. The troclear nerve (CNIV) also causes double vision when damaged resulting in a short of twisting of the eye within the socket. Patients can cancel out the distortion by awkwardly tilting their heads.

"Brain birth" is a concept analogous to brain death accepted by some proponents of abortion rights that states that, just as adults who have been rendered irreparably unconscious are declared legally dead before their heart and lungs have stopped working, unborn fetuses should not be considered alive until the brain had developed enough to be meaningfully useful.