Contractures and paralyses will often last for years and will then unexpectedly and suddenly pass off. In general, there is no limit to the curability of hysterical disorders, and it is characteristic for a disturbed function, after being interrupted for years, to be suddenly restored to its full extent. On the other hand, the development of hysterical disorders often calls for a sort of incubation, or rather for a period of latency, during which the provoking cause continues to operate in the unconscious. Thus, a hysterical paralysis scarcely ever emerges immediately after a trauma; people involved in a railway accident, for instance, are all able to move after the trauma, they go home apparently unhurt, and it is only after days or weeks that the phenomena are generated which lead to the assumption of a 'concussion of the spinal cord'. So, too, the recovery which suddenly sets in usually requires a period of several days for its development. In any case, it may be asserted that hysteria never, even in its most threatening manifestation, involves a serious risk to life. Moreover, complete intellectual clarity and a capacity even for unusual achievements is retained in the most protracted cases of hysteria.
http://theworld.com/~awolpert/gtr521.html
Draft of July 27.2004