moondaughter, thanks for bringing up this subject. See this article [1] (behind a paywall):
"An 81-year-old male with a 12-year history of Parkinson disease sought chiropractic care. He had a stooped posture and a shuffling gait. ... The patient was treated with blue-lensed glasses, vibration stimulation therapy, spinal manipulation, and eye-movement exercises. Within the first week of treatment, there was a reduction in symptoms, improvement in ambulation, and tremor."
This is only one case, but it is worth looking into it in more detail.
The issue is whether AHS causes PD, or the other way round.
Reference
[1] "Chiropractic Management of an 81-Year-Old Man With Parkinson Disease Signs and Symptoms"
Joesph Bova, AdamSergent
Journal of Chiropractic Medicine, June 2014
Chiropractic Management of an 81-Year-Old Man With Parkinson Disease Signs and Symptoms - ScienceDirect
John