 In determining a diagnosis between with catatonia, akinetic mutism, and FCMS, a person must demonstrate their ability to perform voluntary function of the limbs.Patients with catatonia or akinetic mutism are not able to perform voluntary commands that involve the use of limbs, while patients with FCMS still possess voluntary usage of limbs.If a person can demonstrate ability in voluntary usage of limbs, catatonia and akinetic mutism are most likely ruled out from the diagnosis.