Dromomania

Dromomania, also called travelling fugue', is a psychological condition in which people spontaneously depart their routine, travel long distances and take up different identities and occupations. Months may pass before they return to their former identities.

The most famous case was that of Jean-Albert Dadas, a Bordeaux gas-fitter. Dadas would suddenly start travelling, on foot, and come to as far away as Prague or Vienna or even Moscow with no memory of his travels. A medical student, Philippe Tissie, wrote about Dadas in his doctoral dissertation in 1887.

Jean-Martin Charcot presented a similar case he called automatisme ambulatoire.

Only a handful of cases were ever documented, nearly all in France in the late nineteenth century.

See Mad Travellers: Reflections on the Reality of Transient Mental Illnesses by Ian Hacking (ISBN 1-85343-455-8)