I am currently researching the Cranial Nerves and their functions. My interest in this area was piqued because many of the major and common symptoms of Parkinson's Disease are not properly explained by just the "death of dopamine producing cells in the Substantia Nigra" scenario. However, I do believe that the atrophy of the Cranial Nerves in people with Parkinson's (PwP) does very straightforwardly explain most of the main secondary symptoms, and in a very common sense way.