I am 59 and for over a year suffer intense searing/burning pain inside my ankle, a sort of nerve pain. I am basically in intense agony for about 10 to 20 seconds. Are you sure you are suffering a cramp and not a nerve pain. I have had a CT scan and MRI and nothing has been detected. And I have tried an acupuncturist . This has reduced the intensity of the attack when it comes ( which is out of the blue, now about 12 times in over a year).
But I am beginning to think it may be related to when I imbibe a little too much RED WINE. I cannot be certain yet, but I think each attack may follow red wine consumption. About 4 to 10 hours after the event. I have ruled out walking down hill, drumming( I think!).
A visit to an acupuncturist may help. Mine is marvellous. I hope you find an answer,and feel for your plight.