Grading of hepatic encephalopathy categorizes it in clinical stages of stepwise worsening. The description of each grade varies somewhat in the literature, but differences between adjacent grades are clear enough to be helpful in clinical practice, although neurologic descriptors are sparse. One study showed that for patients who become comatose, the Full Outline of Unresponsiveness (FOUR) score is more discriminating than the West Haven grading system because it includes brain-stem and respiration assessment, which are not further differentiated in the West Haven system.
Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by the reactivation of a ubiquitous polyomavirus JC (JCV). PML was for many years a rare disease occurring only in patients with underlying severe impaired immunity.