Yes, when it happens it happens so quick, often when I tilt my neck-head forwards, but I try my utmost never to let that happen, even now when washing my hair in the shower room. I dont understand how this sensation happens but it runs from the back of my neck to the inside of the top of my right leg. Before I knew of this word- this name, I had experience this when washing my hair over the sink as I once did before my MS diagnoses, something strange was happening to my leg where I then had to stand with my right leg stretched backwards when I tilted my head forwards into the sink, at that time I had no clues as to what was happening, it is only now I have a name put to it, Lhermitte Sign.
I must mention that this had me down on one occasion. I was stupid a couple of years ago to take myself into the bathroom and wash my hair with the baths hand shower over the bath. Even though I kept my head up as straight as I could, and I remained standing straight with just a slight tilt over the edge of the bath, I briefly closed my eyes whilst the shower head went over my face and my eyes had shampoo on them, that was a silly thing to have done, once my eyes were closed, just for a brief second or two, I slowly went down to the floor, not heavily, I knew I was going down, thank heavens I never passed out. Not something I shall try again, once was enough, now I wash my hair standing up in the shower, I always lean back on the wall for steadiness, preventing myself from falling backwards.
Jackie