Progressive Supranuclear Palsy
Some links...
http://www.ninds.nih.gov/disorders/psp/detail_psp.htmhttp://www.mayoclinic.org/diseases-conditions/progressive-supranuclear-palsy/basics/definition/con-20029502A quick overview...
Hits people over 60 (she started having issues in her early 60's), would explain her difficulties in balance:
Would explain her "seizures" and other odd head movements/behavior
Would explain the Fresnel prisms she has been seen wearing:
And yup, it would explain her coughing as its a common symptom due to the difficulty in swallowing:
https://healthunlocked.com/psp/posts/32609/what-causes-psp-sufferers-to-cough-so-muchAlso explains some of there other odd behavior, and why she's very controlled in the settings she is seen in.
