If what you are experiencing is L'Hermittes it is caused by a lesion(s) on the cervical spine. There are other causes for L'Hermittes and is not exclusive to MS.

When you bend your head down you get sensations ( electric shock, vibrations/buzzing) for a second or two but the sensation can be repeated everytime you bend your head down.

I have had this symptom for 23 years. For me it's not painful just annoying. I get vibrations/buzzing from mid spine down. There really isn't anything you can do about L'Hermittes. If you have pain with it your neuro can try some meds for pain but it won't stop the L'Hermittes.

Here is more information about L'Hermittes:
http://www.themcfox.com/multiple-scl...ittes-sign.htm