Sorting out subacute encephalopathy

Chronic encephalopathies lead to dementia syndromes that develop over months or years in a setting of clear consciousness (Neary & Snowden 2002). By contrast, acute encephalopathies are neurological and neurosurgical emergencies associated with rapid and severe disturbance of consciousness over hours or days, causing delirium, stupor and ultimately coma (Bateman 2001). Subacute encephalopathies are in between – impaired consciousness develops insidiously over weeks or months. The term ‘confusional state’ is applicable to subacute encephalopathies. However, the clinician may also be confused. For example, patients with chronic dementia are sometimes inappropriately described as ‘confused’, while patients who are in a genuine confusional state may not be recognized as such. Diagnostic mistakes are particularly likely in older people who are sometimes thought, even nowadays, to be inherently senile and demented. Moreover, the situation is complicated by the fact that people who do have dementia may develop transient confusional states following acute perturbations