an anatomy link - ankle
http://mywebpages.comcast.net/wnor/ankle.htm
http://www.meddean.luc.edu/lumen/Med...s/main_art.htm
on one site image that I saw it shows the blood vessel running right next to the nerve so if swollen it could be impinging on the nerve - thus the zaps.
keep an eye on it for any changes or worsening.