I have had a similar sensation before, but not in years, and not on my head. I think mine was a manifestation of lhermitte's sign and I mostly felt it in my feet. I described it then as a kind of 'carbonated' feeling. usually would occur after some sort of mild exertion like walking across a parking lot. not sure exactly what the cause of this sensation could be, but I don't associate it with positive processes. I could be wrong but I just don't get the sensation any more. that said, your wife could be experiencing something entirely different. question: has she had all her levels done any time recently? if so, how did they look?
my approach: no meds so far - just nutrient-dense anti-inflammatory whole foods, and supplements where needed
info: www.whfoods.com, www.nutritiondata.com