Delirium is a syndrome characterized by confusion with inattention, alteration of arousal, disorientation, and global cognitive impairment. All patients with delirium should be promptly evaluated because of the progressive and potentially lethal nature of many of the etiologic factors as well as the danger these patients may pose to themselves. Management of the underlying cause leads to resolution in most circumstances. In this chapter, the terms delirium and confusion are used interchangeably.
All physicians encounter delirious patients during their careers, and knowing the patients at risk for delirium improves early recognition of the syndrome. The point prevalence of adults in the general population older than 55 years is 1.1%. About 10% to 40% of the hospitalized elderly and 60% of nursing home patients older than 75 years are delirious. Patients with cancer, AIDS, or a terminal illness and those who have undergone bone marrow transplantation and other surgical procedures are at increased risk of delirium.
I. ETIOLOGY
The common pathophysiologic mechanism of all causes of delirium is widespread dysfunction of both the cortical and the subcortical neurons.
A. The causes can affect a focal population or disrupt neuronal functioning diffusely.
B.The neurotransmitters acetylcholine and dopamine
are known to play a central role in the regulation and communication of large numbers of neurons.
1. Cholinergic neuronal pathways
serve almost all areas of the brain and participate in most executive brain functions, including those of a delirious patient.
2. Dopaminergic neurons
are primarily found in the nigrostriatal, hypothalamic-pituitary, and ventral tegmental areas but diffusely project to the frontal and temporal areas responsible for delirious symptoms.
3. Intoxication with dopamine agonists commonly causes delirium.
4. Antidopaminergic (neuroleptics) actions are commonly used to manage delirium.
The causes of delirium (
Table 1.1) include commonly encountered and rare conditions. Many are reversible and carry an excellent prognosis if the patient is treated in a timely manner. The following are the basic etiologic categories of delirium.
A. Infection
is one of the most common causes of delirium.
1. Systemic infections always should be considered, especially with elderly patients and those with previous brain damage.
2. CNS infections should be a primary consideration in the postoperative neurosurgical and immunosuppressed patients.
B. Metabolic abnormalities
are a common cause of delirium and often coexist with other precipitants of delirium.
C. End-organ failure
manifests as striking abnormalities at general physical examination and usually is readily recognized.
1. Failure to promptly control hypotension and hypoxia can allow patients to suffer severe brain damage.
2. Liver and kidney failure can cause delirium alone or decrease the metabolism and excretion of certain medications and their metabolites.
D. Endocrinopathy
manifests as abnormalities of multiple organ systems and usually has a subacute onset.
E. Nutritional deficiencies
most often (in the United States) affect patients with alcoholism, systemic cancer, and malabsorption syndromes.
F. Intoxication
with and withdrawal from illicit drugs and alcohol can be life threatening and necessitate prompt recognition and timely intervention.
G. Medications
cause delirium among patients who have impaired renal and liver function or interference with metabolism from other drugs especially those with anticholinergic and dopaminergic properties.
H. Hemorrhage and infarction
in the CNS that cause delirium usually are associated with focal neurologic signs and are an emergency, frequently necessitating neurosurgical intervention.
I. CNS trauma
can cause concussion, brain contusion, and epidural and subdural hematoma, each potentially manifesting as a confused state with associated focal neurologic features.
Approach to the Patient with Sleep Disorders
Approach to the Hyperkinetic Patient
Approach to the Patient with Lower Extremity Pain, Paresthesias, and Entrapment Neuropathies
Approach to the Patient with Chronic and Recurrent Headache
Epilepsies in Children
Neuroimaging of Common Neurologic Conditions
