Confusion is defined as the inability to maintain a coherent stream of thought or action. The level of consciousness is reduced in confusional states, and this can be the predecessor of stupor or coma if the underlying cause is not found and reversed. Confusion presents a unique challenge in acquiring the history. In patients who are confused, the organ system that is required to report on symptoms (the central nervous system [CNS]) is itself impaired. For that reason, clinicians must obtain most of the historical information from caregivers and family members. Although this poses an extra level of challenge in acquiring accurate historical information, the history is important to determine the correct diagnosis. Often an acute confusional state is superimposed on a dementia, and demented patients are particularly vulnerable to become confused, given an appropriate precipitant. This syndrome has been called “beclouded dementia.” The diagnosis of delirium is missed in up to 40% to 60% of those affected, and its presence indicates a worse prognosis with higher hospital readmission rates and 30-day mortality, especially if untreated.

Attentional mechanisms function at a subconscious level to allow for normal cognitive and motor function.

Selectivity: To permit effective learning, humans must pay attention to selective stimuli and ignore other surrounding stimuli. In evolutionary terms, the predator must follow the trail of its prey while disregarding other distracting stimuli in its environment.

Coherence: This implies the ability to maintain selective attention over time.

Distractibility: The degree to which the focus of attention is disrupted and shifted to other coincident and simultaneous stimuli.

Universality: The monitoring system must register as many environmental stimuli as possible.

The attentional matrix is regulated at the cortical level by a distributed network of neurons in the parietal and frontal lobes. Diffuse thalamocortical connections regulated by the reticular formation project to and activate the cortex. The right hemisphere is dominant for the overall attentional matrix, and structural causes of confusion are mainly right-sided. Confusion results from disruption in the attentional matrix at the cortical or subcortical level.

Causes of confusion can be subdivided into three large categories:

When confusion develops in hospitalized patients, it generally occurs in those with predisposing risk factors (Inouye, 1996). A severe insult can cause confusion even in patients at low vulnerability, but a relatively mild insult can trigger it in those with multiple risk factors (Table 10.1).

Confused patients are inattentive and distractible. Patients cannot interact with the examiner in an orderly, goal-directed, and coherent fashion. On the motor side, there is often a history of difficulties with sequential goal-directed movements.

The cognitive signs may include some or all of the following: agitation, playful behavior or unconscious humor, use of occupational jargon, and paramnesia. There may also be hallucinations, ideas of reference, and disorientation. Patients are usually amnestic for the event on recovery.