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.
1 Encephalopathy and Delirium
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 chronicity 2 :
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 brain 2
1.1.2 Causes of Encephalopathy
See Table 1‑1.
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. | |
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
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
1.2 Delirium
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 in Criteria A and C are not better 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
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.
A description of a patient in terms of the DSM 5 criteria could look like “Acute, hypoactive delirium due to sepsis.”
1.2.4 Risk Factors for Delirium
Delirium involves a multifactorial etiology ranging from patient vulnerability to delirium at the time of admission and the occurrence of noxious insults during hospitalization. 9 See Table 1‑3.
1.2.5 Clinical Assessment
Assessment begins in the intensive care unit (ICU) setting for the level of arousability, ranging from sedation to agitation, prior to assessing level of consciousness and subsequent delirium. 13
Arousability Assessment Tools
Richmond agitation sedation scale (RASS): See Table 1‑4. A 10-point scale ranging from +4 to −5, created to assess sedation and agitation in the adult patient admitted to the ICU. A RASS score of 0 denotes a calm and alert patient. Positive RASS scores indicate positive or aggressive symptoms. Negative RASS scores differentiate between response to verbal commands (−1 to −3) and physical stimulus (−4 to −5). 3
Ramsay score: See Table 1‑5. It defines the conscious state from a level 1: the patient is anxious, agitated, or restless, through to the continuously sedated level 6: the patient is completely unresponsive. 14
Riker sedation agitation scale (SAS): See Table 1‑6. It was developed in 1999 with the goal of clearly defining and providing more inclusive levels of sedation and agitation than the Ramsay score. 15
Ramsay sedation scale | Description |
1 | Anxious, agitated, restless |
2 | Cooperative, oriented, tranquil |
3 | Responsive to commands only |
4 | Brisk response to light glabellar tap or loud auditory stimulus |
5 | Sluggish response to light glabellar tap or loud auditory stimulus |
6 | No response to light glabellar tap or loud auditory stimulus |
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
