Spontaneous levitation may be displayed by an alien limb, more usually an arm than a leg, indicative of parietal lobe pathology. It is most often seen in corticobasal (ganglionic) degeneration, but a few cases with pathologically confirmed progressive supranuclear palsy have been reported.
Brunt ER, van Weerden TW, Pruim J, Lakke JW. Unique myoclonic pattern in corticobasal degeneration. Movement Disorders 1995; 10: 132-142