IMHO....is not so much the specific symptoms but that misalignment of the upper cervical vertebrae - caused by the head injury - might be causing the symptoms you are experiencing.....as was the case with Greg. I hope you can locate a good Upper Cervical Chiropractor and have x--rays taken to determine if you have such misalignment(s). It's likely a neuro will dismiss this, but it's the first place I'd look. You may also want to google Erin Elster a chiro who''s done studies of PD patients w/ Upper cervical probs...they ALL had them! As do I! Good luck ...and let me know what you find.
Ibby
Maybe your brother could benefit, too??