Beware of the patient who can't open his/her eyes but is otherwise awake!
This coma mimic is the result of eyelid apraxia, which is the inability to voluntarily open eyes despite intact frontalis muscle contraction and absent oculomotor dysfunction.
This can be seen in injuries of the nondominant hemisphere (e.g. R MCA stroke), medial frontal lobe, bilateral thalami (e.g. bilateral thalami stroke), and brainstem (e.g. progressive supranuclear palsy).
When asking these patients to open their eyes, they may use their forehead muscles to try and raise their eyelids.