Glaucoma is a chronic optic neuropathy characterized by retinal ganglion cell death resulting in damage to the optic nerve head and the retinal nerve fiber layer.

Especially challenging are those that result from head injuries, whether minor or severe, that disrupt the function of the body's smell receptors - olfactory nerve cells that lie outside the brain.

The gut. Do you know you have more nerve endings in your stomach than in your head?