Akinesia

Akinesia (from the prefix a-, "without", and the Greek κίνηση, kinisi, "motion") is the inability to initiate movement due to difficulty selecting and/or activating motor programs in the central nervous system. Common in severe cases of Parkinson's disease, akinesia is a result of severely diminished dopaminergic cell activity in the direct pathway of movement.

Akinetic Mutism
Akinetic mutism is a condition in which a person is both mute and akinetic. A textbook on clinical neurology observes that a person with akinetic mutism has "sleep-waking cycles but, when apparently awake, with eyes open, lies mute, immobile and unresponsive." Some dictionaries describe it as "loss of normal muscle tone."