Patients With Neurocognitive Disorders

As life expectancy extends and the baby boomer generation begins to reach geriatric age, we will confront an epidemic of neurocognitive disorders (NCDs) in general hospitals. The number of cases of Alzheimer's disease (AD), the most common cause of NCD, is expected to quadruple in the coming decades. Unfortunately, most NCDs (used interchangeably in this chapter with the term “dementia”), including AD, are incurable, but progression can be slowed if the condition is identified and managed appropriately; only a few neurocognitive illnesses are reversible. Given that a major task for consultation psychiatrists is to assist in the diagnosis and treatment of NCDs, this chapter provides an overview of these disorders and an approach to their identification and management.

Often, the request to see an inpatient on a medical or surgical floor is for a behavioral disturbance associated with delirium, not for cognitive difficulties alone. Nonetheless, the risk of developing delirium is between two to five times higher in patients with a NCD, and an episode of delirium may unmask a previously undiagnosed NCD. Conversely, delirium itself is also a risk factor for later development of a NCD. Thus, the presence of delirium in an elderly patient should lead the consultant to conduct a thorough evaluation in search of a potentially coexisting NCD.

Another common request is for the evaluation of depressive symptoms associated with a NCD. It may be challenging to determine whether the mood symptoms are causing, coexisting with, or resulting from neurocognitive difficulties. Determining the sometimes subtle differences in the history and presentation of delirium, depression, and AD, can be helpful in the diagnosis of these disorders ( Table 11-1 ).

TABLE 11-1

Clinical Features of Delirium, Depression, and Alzheimer's Disease

	DELIRIUM	DEPRESSION	ALZHEIMER'S DISEASE
Onset of initial symptoms	Abrupt	Relatively discrete	Insidious
Onset of initial symptoms	Difficulty with attention and disturbed consciousness	Dysphoric mood or lack of pleasure	Memory deficits—verbal and/or spatial
Course	Fluctuating—over days to weeks	Persistent—usually lasting months if untreated	Gradually progressive, over years
Family history	Not contributory	May be positive for depression	May be positive for AD
Memory	Poor registration	Patchy/inconsistent	Recent > remote
Memory complaints	Absent	Present	Variable—usually absent
Language deficits	Dysgraphia	Increased speech latency	Confrontation naming difficulties
Affect	Labile	Depressed/irritable	Variable—may be neutral

Other presenting problems should alert the physician to an underlying NCD. These include poor medication adherence and injuries that could be accounted for by memory impairment. For example, many elderly patients experience burns as a result of dangerous cooking methods. Another reason for referral may be the patient's difficulty in coping with the inpatient setting itself. Despite a gradual cognitive decline, the patient may have functioned adequately in his or her familiar home setting. In the alien environment of the hospital, however, unfamiliar people provide care on an unusual schedule. As a result, trusted coping mechanisms may fail; anxiety, dysphoria, agitation, or paranoia can develop.

Case 1

Mr. G, a 74-year-old retired chef without a known psychiatric history and a medical history significant for hypertension, was admitted for treatment of gout after 2 days of worsening foot and knee pain. Colchicine therapy was initiated. His first 24 hours passed uneventfully but on his second night, he abruptly yelled at his nurse and showed “aggressive posturing” while she was attempting to take his evening vital signs. Psychiatry was consulted for evaluation and management of this behavior.

On interview, Mr. G was alert and agitated; however, he was oriented only to name and “a hospital” and could not state why he had been admitted. He told the consultant, “the nurses stole my clothes and my wallet! I'm going home! Where's my wife?” The consultant calmly heard Mr. G's concerns and offered reassurance that his belongings had been stored for safekeeping while he was in the hospital. Mr. G remained suspicious, but calmed somewhat after the consultant requested that staff retrieve his belongings and bring them to the patient.

When Mr. G's wife arrived for evening visitation hours, the consultant was able to organize a discussion with her, the nurse, and the night-float resident, whereby the reason for hospitalization was revisited with Mr. G. An interview conducted with Mr. G's wife alone revealed that he had got lost several times recently, and that she had taken over paying bills due to errors he had made over the past year. He had also become “confused” during a family trip the previous summer.

For the duration of his stay, Mr. G's personal effects were placed around him to create an atmosphere of familiarity, and the entire team worked to ensure that he was frequently re-oriented to date, location, and the purpose of admission. He was discharged without further incident, and an outpatient neuropsychology appointment was arranged.

Epidemiology

Improvements in public health, nutrition, and medical care for the elderly have led to a dramatic increase in the US population over the age of 65. Furthermore, those who live beyond the age of 90, the so-called oldest old, are the fastest-growing segment of the US population. The significance of the aging population lies in the fact that age is a risk factor for dementia. Although the results of epidemiologic studies vary depending on the subjects sampled and the method employed, dementia occurs in approximately 14% of all individuals over the age of 71, rising to 37% in those over the age of 90 and 50% in older non-agenarians. The global prevalence of dementia was estimated at over 35.6 million people in 2010; the number of people affected will double every 20 years, reaching over 115 million by 2050.

The most common type of dementia (accounting for 50% to 70% of cases) is AD. Vascular dementia (which can have a number of different etiologies) is the second most common type of dementia and can exist independently, but frequently co-occurs with other dementias, especially AD. Dementia with Lewy bodies (DLB) is the next most common, followed by the less common forms of dementia, such as frontotemporal dementia (FTD), dementias associated with Parkinson's disease, and Creutzfeldt–Jakob disease (CJD).

Diagnosis

In an effort to define disorders characterized by cognitive dysfunction, the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) has replaced the term “dementia” with “major neurocognitive disorder”. The diagnosis of major NCD has also changed; memory impairment is no longer necessary but instead there must be a significant decline from previous level of functioning in at least one cognitive domain (e.g., memory, executive function, language, or social cognition).

Features of various NCDs may include aphasia (a difficulty with any aspect of language), apraxia (the impaired ability to perform motor tasks despite intact motor function), agnosia (an impairment in object recognition despite intact sensory function), or a disturbance of executive function (including the ability to think abstractly, as well as to plan, initiate, sequence, monitor, and stop complex behavior). Associated features include impaired judgment, poor insight, personality change, and psychiatric symptoms (e.g., persecutory delusions and hallucinations, particularly visual). Motor disturbances (falls, ataxia, parkinsonism, and extrapyramidal signs) and dysarthria (slurred speech) may be associated with certain NCDs.

Additional essential elements for a diagnosis of a major NCD include a significant impact on independent functioning and the occurrence of impairment outside the exclusive context of a delirium. These final criteria are necessary to rule out age-associated memory impairment, congenital mental retardation, and life-threatening acute confusional disorders.

Scores of specific disorders can cause cognitive impairment ( Table 11-2 ). The consultant cannot have in-depth knowledge of all of them but can identify common or typical and rare or unusual presentations. In addition, certain associated physical findings can direct the consultant to particular diagnoses ( Figure 11-1 ).

Table 11-2

Causes of Cognitive Impairment: Diagnoses by Categories With Representative Examples

Degenerative

Alzheimer's disease
Frontotemporal dementias
Dementia with Lewy bodies
Corticobasal degeneration
Huntington's disease
Wilson's disease
Parkinson's disease
Multiple system atrophy
Progressive supranuclear palsy

Psychiatric

Depression
Schizophrenia

Vascular

Vascular dementia
Binswanger's encephalopathy
Amyloid dementia
Diffuse hypoxic/ischemic injury

Obstructive

Normal-pressure hydrocephalus
Obstructive hydrocephalus

Traumatic

Chronic subdural hematoma
Chronic traumatic encephalopathy
Post-concussion syndrome

Neoplastic

Tumor—Malignant—primary and secondary
Tumor—Benign (e.g., frontal meningioma)
Paraneoplastic limbic encephalitis

Infections

Chronic meningitis
Post-herpes encephalitis
Focal cerebritis/abscesses
HIV dementia
HIV-associated infection
Syphilis
Lyme encephalopathy
Subacute sclerosing panencephalitis
Creutzfeldt–Jakob disease
Progressive multifocal leukoencephalopathy
Parenchymal sarcoidosis
Chronic systemic infection

Demyelinating

Multiple sclerosis
Adrenoleukodystrophy
Metachromatic leukodystrophy

Autoimmune

Systemic lupus erythematosus
Polyarteritis nodosa

Drugs/Toxins

Medications

Anticholinergics
Antihistamines
Anticonvulsants
β-blockers
Sedative–hypnotics

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