Diencephalic syndrome (DS) is a rare condition characterized by profound emaciation and failure to thrive (with normal caloric intake and normal linear growth), hyperalertness, hyperkinesia and euphoria, in the presence of hypothalamic tumors.

Muscular hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle), often involving reduced muscle strength. Hypotonia is characterized by a diminished resistance to passive stretching.