Combined resting-postural tremor of the head with a changing axis.

When essential tremor involves the head, it produces a rhythmic, periodic movement with a certain fixed frequency and a variable amplitude. The axis of the tremor has been described as either horizontal (no-no) or vertical (yes-yes) and is present when the head is in an action or postural position. Seven patients who differ in symptoms are described; one subgroup exhibited a combined resting-postural tremor of the head, sometimes with a changing axis; three patients had only postural head tremor with a changing axis.