Delirium history and symptoms

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vishal Khurana, M.B.B.S., M.D. [2] Pratik Bahekar, MBBS [3]

History and Symptoms

• Thorough history including:

  • Incoherent speech
  • Memory difficulties
  • Disorientation
  • Level of attention
  • Conversations with family and/or caregivers of patient

• Performance of abbreviated mental exam

Risk Factors

• Older age
• Cognitive impairment / dementia
• Physical comorbidity (biventricular failure, cancer, cerebrovascular disease)
• Psychiatric comorbidity (e.g. depression)
• Sensory impairment (vision, hearing)
• Functional dependence (e.g. requiring assistance for self-care and/or mobility)
• Dehydration / Malnutrition
• Drugs and drug-dependence.
• Alcohol dependence

Precipitating factors

Any acute factors that affect neurotransmitter, neuroendocrine or neuroinflammatory pathways can precipitate an episode of delirium in a vulnerable brain. Clinical environments can also precipitate delirium, and optimal nursing and medical care is a key component of delirium prevention. Some of the most common precipitating factors are listed below:

• Metabolic
• Malnutrition
• Dehydration, electrolyte imbalance
• Anaemia
• Hypoxia
• Hypercapnoea
• Hypoglycaemia
• Endocrine disorders (e.g. SIADH, Addison’s disease, hyperthyroidism, hypercalcaemia)
• Infection
• Especially respiratory and urinary tract infections
• Medication
• Anticholinergics, dopaminergics, opioids, steroids, recent polypharmacy
• Vascular
• Stroke/Transient ischaemic attack
• Myocardial infarction, arrhythmias, decompensated heart failure
• Physical/psychological stress
• Pain
• Iatrogenic event, esp. post-operative, mechanical ventilation in ICU
• Chronic/terminal illness, esp. cancer
• Post-traumatic event, e.g. fall, fracture
• Immobilisation/restraint
• Other
• Substance withdrawal, esp. alcohol, benzodiazepines
• Substance intoxication
  • Traumatic head injury

Differential Diagnosis

Differential points from other processes and syndromes that cause cognitive dysfunction:

Psychiatric Disorders

• Delirium may be distinguished from psychosis, in which consciousness and cognition may not be impaired (however, there may be overlap, as some acute psychosis, especially with mania, is capable of producing delirium-like states).
• Delirium is distinguished from depression.
• Mania should be differentiated from hyperactive delirium. Previous history of bipolar disorder is useful in distinguishing delirium from mania.
• Delirium is distinguished by time-course from the confusion and lack of attention which result from long term learning disorders and varieties of congenital brain dysfunction. Delirium has also been referred to as 'acute confusional state' or 'acute brain syndrome'. The key word in both of these descriptions is "acute" (meaning: of recent onset), since delirium may share many of the clinical (i.e., symptomatic) features of dementia, developmental disability, or attention-deficit hyperactivity disorder, with the important exception of symptom duration.
• Delirium is not the same as confusion, although the two syndromes may overlap and be present at the same time. However, a confused patient may not be delirious (an example would be a stable, demented person who is disoriented to time and place), and a delirious person may not be confused (for example, a person in severe pain may not be able to focus attention because of the pain, and thus be by definition delirious, but may be completely oriented and not at all confused).

Dementia

• Delirium is distinguished from dementia (chronic organic brain syndrome) which describes an "acquired" (non-congenital) and usually irreversible cognitive and psychosocial decline in function. Dementia usually results from an identifiable degenerative brain disease (for example Alzheimer diseaseorHuntington's disease). Dementia is usually not associated with a change in level of consciousness, and a diagnosis of dementia requires a chronic impairment.
• Sundowning: Typically observed in patients suffering from dementia. It's an impairment in behavioral patterns in the evening hours. Similar symptomology can be observed in the patients suffering from other ailments such as impaired cincardial rhythm. New onset in change in behavioral patterns should always be assessed carefully and diagnosis of delirium should be considered.

Other Neurological Disorders

• Frontal lobe disorders such as tumor can produce deficits in memory, distorted emotional responses, impaired judgment, etc. Imaging studies and focal neurological symptoms may be helpful to differentiate from delirium.
• Temporal lobe disorders may lead to memory deficits, cortical deafness, visual agnosia, etc. Imaging studies and focal neurological symptoms may be helpful to differentiate from delirium.
• Occipital lobe disorders can demonstrate various symptoms such as confabulation, cortical blindness, etc. Imaging studies and focal neurological symptoms may be helpful to differentiate from delirium.
• Parital lobe disorders like Wernicke's aphasia can hinder patient's ability to follow examiner's instructions which is often misinterpreted as a state of confusion.
• Nonconvulsive epileptic episodes should also be considered as a differential diagnosis of delirium.

Delirium represents an organically caused decline from a previously attained level of cognitive functioning. It is a corollary of these differential criteria that a diagnosis of delirium cannot be made without a previous assessment, or knowledge, of the affected person's baseline level of cognitive function. In other words, a mentally disabled or demented person who is operating at their own baseline level of mental ability might appear to be delirious without a baseline functional status against which to compare.

Commonly co-occurring mental symptoms, with a note on severity

Since delirium may occur in very many grades of severity, all symptoms may occur with varying degrees of intensity. A mild disability to focus attention may result in only a disability in solving the most complex problems. As an extreme example, a mathematician with the flu may be unable to perform creative work, but otherwise may have no difficulty with basic activities of daily living. However, as delirium becomes more severe, it disrupts other mental functions, and may be so severe that it borders on unconsciousness or a vegetative state. In the latter state, a person may be awake and immediately aware and responsive to many stimuli, and capable of coordinated movements, but unable to perform any meaningful mental processing task at all.

Inability to focus attention, confusion and disorientation

The delirium-sufferer loses the capacity for clear and coherent thought. This may be apparent in disorganised or incoherent speech, the inability to concentrate (focus attention), or in a lack of any goal-directed thinking.

Disorientation (another symptom of confusion, and usually a more severe one) describes the loss of awareness of the surroundings, environment and context in which the person exists. It may also appear with delirium, but it is not required, as noted below. Disorientation may occur in time (not knowing what time of day, day of week, month, season or year it is), place (not knowing where one is) or person (not knowing who one is).

Cognitive function may be impaired enough to make medical criteria for delirium, even if orientation is preserved. Thus, a patient who is fully aware of where they are and who they are, but cannot think because they cannot concentrate, may be medically delirious. The state of delirium most familiar to the average person is that which occurs from extremes in pain, lack of sleep, or emotional shock.

Because most high level mental skills are required for problem solving, including ability to focus attention, this ability also suffers in delirium. However, this is a secondary phenomenon, since problem-solving involves many sub-skills and basic mental abilities, any of which may be impaired in a delirious patient.

Memory formation disturbance

Impairments to cognition may include temporary reduction in the ability to form short-term or long-term memory. Difficult short-term memory tasks like ability to repeat a phone number may be continuously disrupted during a delirium, but easier short-term memory tasks like repeating single words, or remembering simple questions long enough to give an answer, may not be impaired. Reduction in formation of new long-term memory (which by definition survive withdrawal of attention), is common in delirium, because initial formation of (new) long-term memories generally requires an even higher degree of attention, than do short-term memory tasks. Since older memories are retained without need of concentration, previously formed long-term memories (i.e., those formed before the period of delirium) are usually preserved in all but the most severe cases of delirium (and when destroyed, are destroyed by the underlying brain pathology, not the delirious state per se).

Abnormalities of awareness and affect

Hallucinations (perceived sensory experience with the lack of an external source) or distortions of reality may occur in delirium. Commonly these are visual distortions, and can take the form of masses of small crawling creatures (particularly common in delirium tremens, caused by severe alcohol withdrawal) or distortions in size or intensity of the surrounding environment.

Strange beliefs may also be held during a delirious state, but these are not considered fixed delusions in the clinical sense as they are considered too short-lived (i.e., they are temporary delusions). Interestingly, in some cases sufferers may be left with false or delusional memories after delirium, basing their memories on the confused thinking or sensory distortion which occurred during the episode of delirium. Other instances would be inability to distinguish reality from dreams.

Abnormalities of affect which may attend the state of delirium may include many distortions to perceived or communicated emotional states. Emotional states may also fluctuate, so that a delirious person may rapidly change between, for example, terror, sadness and jocularity.