[1][2] The tremor is caused by abnormal function of the diencephalic motor centers in the brain, which regulate the muscles involved in maintaining position.
[4] Usually there are brief, arrhythmic interruptions of sustained voluntary muscle contraction, causing brief lapses of posture with a frequency of 3–5Hz.
This position should be held for at least 30 seconds, and in that duration the examiner should look for intermittent loss of posture in the fingers, wrists or arms.
[8] Initially Foley and Adams referred to asterixis simply as "tremor" but realized that they needed a more appropriate term.
On a literature search they found a poorly described phenomenon in similar patients mentioned by German physicians called “jactitations” but the reference was vague.