Encephalopathy and Delirium

1 Encephalopathy and Delirium

Catriona M. Harrop

Abstract

Encephalopathy is characterized by the National Institute of Neurological Disorders and Stroke as “any diffuse disease of the brain that alters brain function or structure,”¹ and can be classified as acute or chronic. The definition, diagnosis, and treatment of encephalopathy is reviewed here, along with one of its most common symptoms, delirium.

Keywords: encephalopathy, delirium, confusion, agitation, arousability, Ramsay score, Riker score

1.1 Encephalopathy

1.1.1 Definition

The National Institute of Neurological Disorders and Stroke (NINDS) defines encephalopathy as “a term for any diffuse disease of the brain that alters brain function or structure”¹ with the hallmark of encephalopathy being an altered mental state. Encephalopathy can be categorized by chronicity²:

• Acute

◦ Toxic: due to medications, illicit substances, or toxins

◦ Metabolic: due to a metabolic disturbance

◦ Toxic-metabolic: due to a combination of both

• Chronic: characterized by a slowly progressive alteration in mental status resulting from permanent structural changes within the brain²

1.1.2 Causes of Encephalopathy ³

See ▶ Table 1.1.

1.1.3 Diagnosis of Encephalopathy

Diagnosis is guided by the history and physical examination of the patient. It is considered on a case-by-case basis.

• Laboratory testing

◦ Serum electrolytes

◦ Renal function

◦ Glucose

◦ Calcium

◦ Complete blood count

◦ Urinalysis

◦ Hepatic function

◦ Thyroid function

◦ Drug levels (if applicable), i.e., phenytoin

◦ Drugs of abuse screen

◦ Vitamin levels—B-12, folate

◦ Arterial blood gas

• Imaging

◦ Computed tomography (CT) of brain

◦ Magnetic resonance imaging (MRI) of brain

Table 1.1 Common causes of encephalopathy

Drugs and toxins	Idiopathic Withdrawal states Medication side effects Poisons
Infections	Sepsis Systemic infections Fever
Metabolic derangements	Electrolytes Endocrine disturbance Hypercarbia Hyperglycemia and hypoglycemia Hyperosmolar and hypo-osmolar states Hypoxemia Inborn errors of metabolism Nutritional
Brain disorders	CNS infection Seizures Head injury Hypertensive encephalopathy Psychiatric disorders
Systemic organ failure	Cardiac failure Hematologic Hepatic encephalopathy Pulmonary disease Renal failure
Abbreviation: CNS, central nervous system.

• Evaluation for infections

◦ Lumbar puncture

◦ Blood cultures

• Seizure evaluation

◦ Electroencephalography (EEG)

1.1.4 Treatment of Encephalopathy

• Acute encephalopathy

◦ Based on treatment of the underlying pathophysiology, i.e., treatment of sepsis and hypothyroidism with the potential for reversal of encephalopathy.

• Chronic encephalopathy

◦ Often not amenable to treatment as the inciting insult has caused permanent brain changes, i.e., anoxic encephalopathy.

1.1.5 Relationship to Delirium

Delirium can be characterized as the symptom of the underlying abnormal brain function, i.e., encephalopathy.²

Delirium is a common disorder in hospitalized patients that has significant societal and economic impact.⁴ In-hospital mortality rates reportedly associated with delirium range from 22 to 33%.⁵^,⁶ Currently patients aged 65 years and older account for more than 48% of hospital care; therefore, the impact of delirium on hospitalized patients will continue to grow as our population ages.⁴

1.2.1 Definition

The Diagnostic and Statistical Manual of Mental Disorders (DSM) 5 defines delirium under Neurocognitive Disorders ⁷ which encompasses “the group of disorders in which the primary clinical deficit is in cognitive function, and that are acquired rather than developmental.” The diagnostic criteria are as follows:

• A disturbance in attention (i.e., reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment).

• The disturbance develops over a short period of time (usually from hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.

• An additional disturbance in cognition (e.g., memory deficit, disorientation, language, visuospatial ability, or perception).

• The disturbances are not explained by another pre-existing, established, or evolving neurocognitive disorder and do not occur in the context of a severely reduced level of arousal, such as coma.

• There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct physiologic consequence of another medical condition, substance intoxication or withdrawal (i.e., due to a drug of abuse or a medication), or exposure to a toxin, or is due to multiple etiologies.

As outlined in the DSM 5, Delirium can be further subdivided into:

• Substance intoxication

• Substance withdrawal

• Medication induced

• Another medical condition

• Multiple etiologies

1.2.2 Duration of Symptoms

• Acute: Lasting for a few hours or days

• Persistent: Lasting for weeks or months

1.2.3 Level of Activity (▶ Table 1.2)

• Hyperactive: The individual has a hyperactive level of psychomotor activity that may be accompanied by mood lability, agitation, and/or refusal to cooperate with medical care.

• Hypoactive: The individual has a hypoactive level of psychomotor activity that may be accompanied by sluggishness and lethargy that approaches stupor.

• Mixed level of activity: The individual has a normal level of psychomotor activity even though attention and awareness are disturbed. Also includes individuals whose activity level rapidly fluctuates.