This patient's presentation is most consistent with delirium, which has numerous potential etiologies including infection, surgery or other trauma, or pharmacologic side effects.
Acute onset of symptoms, fluctuating level of consciousness, and presence of visual hallucinations favor a diagnosis of delirium over dementia. Additionally, sleep-wake cycle disturbance is a prominent feature of delirium. Delirium is reversible, while dementia, by contrast, is often irreversible and is typically a diagnosis of exclusion confirmed by histology on autopsy. Clinically, patients with dementia show gradual decline in cognition with preservation of level of consciousness. Additional findings in dementia include aphasia, apraxia, agnosia, behavioral or personality changes, and short-term memory impairment with sparing of remote memory.
Espino et al. discuss the work-up and diagnostic approach in the confused elderly patient. They state that confusion may be a manifestation of dementia, delirium, depression, or psychosis. Given the reversibility of the disease, the confused patient should be assumed to have delirium until proven otherwise. Reversible causes of delirium should be considered, including metabolic disorders, infections, medications, normal pressure hydrocephalus, vitamin deficiencies, or thyroid dysfunction, which may be potentially reversible causes of dementia-like symptoms.
O'Regan et al. discuss the impact of delirium in the perioperative patient. They report that delirium occurs in up to 20% of acute hospital inpatients and up to 60% of surgical patients in the perioperative period. Delirium is commonly co-morbid with dementia in elderly patients; however, identifying and treating the cause of delirium is critical. They conclude that delirium most commonly presents with hypoactive features including withdrawal and reduced spontaneous movement or speech; hyperactive delirium involving agitation and hallucinations is less common despite being more easily detected clinically.
Illustration A is a chart comparing and contrasting clinical characteristics of dementia versus delirium.
Answer 1: Anticholinergic medications may actually exacerbate delirium.
Answer 2: Beta-amyloid plaques and neurofibrillary tangles are common findings in Alzheimer's dementia, not delirium.
Answer 3: This is a clinical manifestation of dementia; delirium, in contrast, is more commonly associated with global memory impairment.
Answer 4: Delirium is generally a reversible process once an underlying etiology is identified and treated; dementia, on the other hand, is typically irreversible, however, it is important to note that it is NOT a component of the normal process of aging.
Espino DV, Jules-Bradley AC, Johnston CL, Mouton CP. Diagnostic approach to the confused elderly patient. Am Fam Physician. 1998 Mar 15;57(6):1358-66. Review.
PMID:9531917 (Link to Abstract)
O'Regan NA, Fitzgerald J, Timmons S, O'Connell H, Meagher D. Delirium: a key challenge for perioperative care. Int J Surg. 2013;11(2):136-44.
PMID:23277227 (Link to Abstract)