Table 1.
Differential diagnosis for akinetic mutism, features, and distinguishing characteristics
| Condition | Features | Distinguishing characteristics from AM |
|---|---|---|
| MCS/PVS | Reduced arousal—typically due to brainstem injury—results in absence of goal-directed behavior | Eye tracking spared in AM and MCS but not in PVS Complex speech or action in response to environmental triggers in AM but not in MCS/PVS |
| Locked-In syndrome | Immobility due to paralysis sparing vertical eye movements and blinking, typically caused by ventral pons/midbrain infarction | Absence of motor paralysis in AM Often some preserved communication via patterned eye movements |
| Polyneuropathy/myopathy | Hypokinesis due to pain and reduced muscular function from muscle and nerve injury in critical illness | Motivation to move remains intact Speech output is not typically limited as in AM |
| Ischemic or hemorrhagic infarct | Hypokinesis due to upper motor neuron injury, typically unilateral NB: A strategic infarct may produce an AM phenotype. |
Motivation to move may be intact Speech output may be aphasic, but mutism is rare |
| Hypoactive delirium | Marked by disorientation, inattention, fluctuating consciousness in the absence of agitation | Affective state is typically distressed or fearful in delirium compared to AM Goal-directed movement—particularly in response to perceptual disturbances—are preserved in hypoactive delirium |
| Nonconvulsive status epilepticus | Presentations are diverse but mutism is common and stuporous non-responsiveness can develop | Often fluctuating presentation with motor automatisms, which are less typical for AM EEG findings may be demonstrative |
| Catatonia | Marked by immobility, mutism, rigidity; may also demonstrate hyperkinetic features such as agitation, stereotypy, mannerisms NB: Catatonia and AM share similar features and may be related pathophysiologic states. |
Affective state is typically fearful AM does not have hyperkinetic features AM does not typically respond to benzodiazepines |
AM = akinetic mutism; MCS = minimally conscious state; PVS = persistent vegetative state.