Abstract
Cognitive disorders in the DSM-IV-TR included delirium, dementia, amnestic disorder, and cognitive disorders not otherwise specified. DSM-V retains the diagnosis of delirium and introduces the term neurocognitive disorder (NCD), dividing NCDs into major NCD or mild NCD and unspecified NCD. The diagnostic category of major NCD encompasses syndromes that were previously categorized as dementia and amnestic disorder. Memory loss is no longer an essential criterion for major NCD in DSM-V as it was for dementia in DSM-IV-TR. Major NCD also includes progressive neurodegenerative dementias, as well as static cognitive disorders that are not expected to worsen over time. The term dementia is retained in DSM-V because of familiarity of the term to the public and medical practitioners.
Delirium, Major or Mild Neurocognitive Disorders
Classification
Cognitive disorders in the DSM-IV-TR included delirium, dementia, amnestic disorder, and cognitive disorders not otherwise specified. DSM-V retains the diagnosis of delirium and introduces the term neurocognitive disorder (NCD), dividing NCDs into major NCD or mild NCD and unspecified NCD. The diagnostic category of major NCD encompasses syndromes that were previously categorized as dementia and amnestic disorder. Memory loss is no longer an essential criterion for major NCD in DSM-V as it was for dementia in DSM-IV-TR. Major NCD also includes progressive neurodegenerative dementias, as well as static cognitive disorders that are not expected to worsen over time. The term dementia is retained in DSM-V because of familiarity of the term to the public and medical practitioners.
According to DSM-V, the two core features of delirium are impairment in awareness (reduced orientation to the environment) and disturbance in attention (impaired ability to direct, focus, sustain, or shift attention). Diagnosis of major NCD, in contrast, requires a significant decline in at least one cognitive domain sufficient to interfere with independence in everyday activities (see Table 11.1). Mild NCD requires the presence of a modest decline in cognitive function not severe enough to interfere with independence in everyday living and to meet criteria for major NCD. Mild cognitive impairment (MCI) will be diagnosed as mild NCD under DSM-V.
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DSM-V links neuropathological etiology with clinical diagnosis of NCD. Major or mild NCD can be due to Alzheimer’s disease, frontotemporal lobar degeneration, Lewy bodies, vascular disease, traumatic brain injury, substances/medications, HIV infection, prion disease, Parkinson’s disease, Huntington’s disease, or another medical condition. Unspecified NCD is applied in situations where symptoms of NCD are present but full criteria for major or mild NCD have not been met.
Delirium
Epidemiology and Impact
Delirium is a very common psychiatric disorder in hospital settings, occurring in up to 24 percent of patients on general medicine floors and almost half of post-operative surgical patients. Delirium is often unrecognized during hospitalization and can persist for weeks to months after the initial episode. Indeed, for almost half of delirious patients, symptoms do not fully resolve until six months after the episode. Older adults, especially those with preexisting cognitive impairment, are more vulnerable to developing delirium.
The long-term complications of delirium include acceleration in cognitive decline and poor functional outcomes, with double the risk of discharge to a nursing home compared to similar hospital patients without delirium. Mortality rates associated with delirium are high, comparable to patients suffering a myocardial infarction or sepsis. The one-year mortality rate attributed to delirium is 35 to 40 percent. Given the difficult hospital course, longer length of stay, frequent need for nursing home and rehabilitation placement as well as home health care services, the health care costs associated with delirium are more than double the costs for comparable patients without delirium.
Clinical Features and Course
As discussed previously, the core features of delirium include (1) inability to direct, focus, sustain, and shift attention and (2) disturbance in awareness (reduced orientation to the environment). Attentional impairments often manifest as distractibility by irrelevant environmental stimuli, difficulty staying on the topic of conversation or the task at hand. Sensorium changes range from lethargy, stupor, obtundation, and may even progress to coma. However, delirium should not be diagnosed in comatose patients. Patients with delirium may appear excessively somnolent or have difficulty staying awake. Sleep-wake cycle is usually disrupted, with patients staying awake at night and sleeping during the day.
The onset of delirium symptoms occurs over the course of hours to days. Symptoms of delirium fluctuate within a twenty-four-hour period and do so more dramatically than seen in other neuropsychiatric disorders. Patients may appear to be at their baseline on cross-sectional examination but can be markedly symptomatic a few hours later. Thus it is important to obtain collateral information from nurses and family members who tend to spend more time with the patient. While patients with more dramatic presentations get diagnosed early, hypoactive symptoms of delirium may be misattributed to depression, leading to a delay in diagnosis.
Patients with delirium usually have significant impairment in multiple cognitive domains, including memory, language, orientation, and executive functions. Abnormalities in thought process may range from mild circumstantiality to disorganized and disjointed speech in more severe cases. Alterations in affective regulation are also common in delirium. Rapid dramatic shifts in affective states (i.e., mood lability) can be quite striking. Patients may appear anxious, apprehensive, and hypervigilant, or withdrawn and apathetic. Hyperactive delirium presents with increased psychomotor activity with agitation and restlessness while hypoactive delirium is characterized by slowed motor activity often with apathy and withdrawal, though it is common to alternate between varying levels of psychomotor activation (mixed delirium).
More than two-thirds of patients with delirium demonstrate psychotic symptoms. Hallucinations may be visual, auditory, or tactile. Unlike in schizophrenia, visual hallucinations are more common than auditory hallucinations in delirium. Delusions due to delirium usually have persecutory themes, tend to be fragmented (non-systematized), and are rarely bizarre. Together with agitation and aggression, psychotic symptoms can pose a risk for patient safety and may result in the disruption of the patient’s medical care (pulling out IV lines or Foley catheter).
Major or Mild Neurocognitive Disorders
Epidemiology and Impact
Age is the most significant risk factor for developing dementia (or major NCD), a disease that increases in prevalence from 3 percent for those aged 65–74 to almost 50 percent in those aged 85 or older. Studies estimate that an additional 14 percent of people over 70 meet criteria for mild cognitive impairment (mild NCD). Of this population, 7–10 percent are estimated to progress to dementia each year. Alzheimer’s disease is the most common cause of dementia (or major NCD), accounting for more than 60 percent of cases and currently affecting 5.8 million Americans. In addition to AD, other important causes of major NCD include vascular dementia (20 percent), dementia with Lewy bodies (15 percent), and frontotemporal dementia (2 percent).
According to the Alzheimer’s Association, the overall cost of health care for patients with dementia, including Medicare and Medicaid spending as well as out-of-pocket costs, will increase from $305 billion in 2020 to $1.1 trillion in 2050. This number does not include the billions of hours of unpaid care provided by family, friends, and neighbors (an average of 21.9 hours per caregiver per week) to patients with Alzheimer’s disease. Many caregivers experience very high levels of emotional stress and are vulnerable to declines in their own physical health. In fact, more than half of caregivers demonstrate significant symptoms of depression, with at least a quarter meeting criteria for major depressive disorder. Providing individual and family counseling and encouraging participation in support groups not only alleviates depressive symptoms in caregivers but can help delay residential care placement for patients themselves.
Mild Neurocognitive Disorder
There is increasing evidence that the neuropathological changes of AD begin well in advance of the onset of clinical symptoms, perhaps decades before a diagnosis of dementia is made. Recent advances in neuroimaging, cerebrospinal fluid analysis, and other biomarkers point to evidence that AD may be best described as a progression along a clinical continuum, from preclinical or pre-symptomatic stages of disease through mild NCD, and then to major NCD. As defined by the guidelines developed by the National Institute of Aging and the Alzheimer’s Association in 2011, the preclinical stage begins with asymptomatic functional and structural brain alterations, including cerebral amyloidosis, synaptic dysfunction, and neurodegeneration that lead to subtle cognitive decline, which can occur years before patients meet criteria for mild NCD. The identification of this preclinical stage is especially important, as it provides a critical opportunity for potentially more effective intervention (Figure 11.1; Table 11.2).
Figure 11.1 Model integrating Alzheimer’s disease immunohistology and biomarkers. The threshold for biomarker detection of pathophysiological changes is denoted by the black horizontal line. The gray area denotes the zone in which abnormal pathophysiological changes lie below the biomarker detection threshold. In this figure, tau pathology precedes Aβ deposition in time, but only early on at a subthreshold biomarker detection level. Aβ deposition then occurs independently and rises above the biomarker detection threshold (arrows with a star). This induces the acceleration of tauopathy and CSF tau and then rises above the detection threshold (arrow with circle). Later still, FDG PET and MRI (arrow with square) rise above the detection threshold. Finally, cognitive impairment becomes evident (arrow with triangle), with a range of cognitive responses that depend on the individual’s risk profile (light-gray-filled area). Aβ = amyloid β. FDG = fluorodeoxyglucose. MCI = mild cognitive impairment. From Jack, C. R., Jagust, W. J., Petersen, R. C., Weiner, M. W., Aisen, P. S., et al. (2013), Tracking Pathophysiological Processes in Alzheimer’s Disease: An Updated Hypothetical Model of Dynamic Biomarkers, Lancet Neurology, 12, 207–216.
| Preclinical Alzheimer’s disease | Mild cognitive impairment (MCI) due to Alzheimer’s disease | Dementia due to Alzheimer’s disease |
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| Measurable biomarker changes (e.g., amyloid accumulation on PET, atrophy on volumetric MRI) occur years before subtle cognitive impairment | Mild changes in memory and thinking are noticeable and can be measured on mental status tests, but are not severe enough to disrupt daily life | Impairments in memory, thinking, and behavior decrease the ability to function independently in everyday life |
In progressive dementias, mild NCD can be the intermediate stage between normal cognitive function and major NCD. Mild NCD is defined by modest cognitive impairment in at least one cognitive domain, not severe enough to affect independence in everyday functions of the individual. Although the day-to-day function is largely intact, a decline in cognitive function can be demonstrated by neuropsychological testing. These cognitive dysfunctions may involve a single domain of cognition (e.g., memory) or multiple cognitive domains (see Table 11.3). It is estimated that as many as 15 percent of those who bring themselves to a physician’s office with symptoms of mild NCD go on to meet criteria for major NCD per year, while others may remain stable or even resolve.
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Mild NCD must also be distinguished from normal age-associated cognitive decline. As speed of processing, attention span, working memory, and speed of learning decline with normal aging, some individuals worry that these changes may be heralding symptoms of a neurodegenerative disease. The diagnosis of mild NCD is warranted only if the severity of cognitive impairment exceeds what would be expected from normal aging.
Major Neurocognitive Disorders
The diagnosis of major NCD requires a significant decline in one or more cognitive domains (complex attention, executive function, learning and memory, language, perceptual-motor, or social cognition). These changes can be discerned from the history and clinical observations, or demonstrated in quantified clinical assessment or neuropsychological testing. Cognitive deficits in major NCD interfere with independence in everyday activities. Now let us briefly discuss the different etiologic subtypes of NCDs.
Neurocognitive Disorder Due to Alzheimer’s Disease (AD)
Symptoms of AD usually begin after fifty years of age and increase in prevalence with advancing age. The initial manifestation of AD is rapid forgetting of newly acquired information. Memory for recent events is impacted early in the course of illness, with increasing difficulty remembering past events as the dementia advances. In AD, the cognitive and functional impairment is insidious in onset and progresses gradually, often over several years.
In the mild stages of AD, the person may recognize his/her memory difficulties. As the illness progresses, others close to the patient will begin to notice memory impairment. Symptoms can include name and word-finding difficulties. Executive deficits may also appear early and worsen with the progression of the illness. Misplacing items, planning, and organizational difficulties for more complex tasks are detected. Forgetfulness for more recent autobiographic events and conversations becomes increasingly apparent.
At the mild stages of the illness, patients can function nearly independently for less complex and routine day-to-day activities. As AD progresses to the moderate stages of the illness, disorientation to time and place and more pronounced autobiographic memory loss (e.g., birth date) become more evident. Day-to-day activities become noticeably impaired at this stage of the illness. In the late stage of the illness, patients become increasingly dependent on others for even basic care (feeding, toileting, etc.). Patients may fail to recognize close family members. In the advanced stage of AD, basic bodily functions such as swallowing and ambulation deteriorate, leading to aspiration pneumonia, decubitus ulcers, and malnutrition. Patients may also develop seizures. These medical co-morbidities ultimately lead to the patient’s demise.
In addition to cognitive decline, patients with AD often develop behavioral and psychological disturbances. These symptoms may first manifest in the mild NCD stage and become more common as the disease progresses. Neuropsychiatric manifestations of AD can include anxiety, depression, mood lability, hallucinations, delusions, agitation, or aggression. Apathy and social withdrawal manifest early in the disease course but become increasingly common as dementia progresses. Patients may appear uninterested in the environment and others around them. In the moderately severe stages of the illness, irritability, agitation, combativeness, wandering, and psychotic symptoms are common.
Psychotic symptoms occur in up to 40 percent of patients with AD and develop often in the moderate stage of illness, while depression occurs in up to 50 percent of patients with AD, often beginning in the early stages of AD. Together with the cognitive impairment and inability to perform activities of daily living, these behavioral and psychological symptoms of AD cause significant distress for the patient, earlier institutionalization, and increased caregiver burden. The average length of survival after diagnosis of Alzheimer’s dementia is four to eight years (although some people live with AD for as long as twenty years).
Vascular Neurocognitive Disorders (VNCD)
VNCD is caused by cerebrovascular insult. VNCD can present with a range of cognitive and clinical symptoms, with complex attention, executive function, and processing speed being typically impaired. Unlike AD, in patients with VNCD, cued recognition memory is better than un-cued recall. Depressive syndromes commonly accompany VNCD. Other features such as personality changes, irritability, and lack of motivation are often seen in VNCD. The course of vascular NCD is also variable. Some patients may exhibit the classic “step-wise” progression, with periods of acute worsening followed by plateaus of relatively stable cognition, while others show a progressive decline.
Neurocognitive Disorder Due to Lewy Bodies (NCDLB)
Although clinically underdiagnosed, NCDLB is the second most common cause of late-onset (onset after sixty-five years of age) neurodegenerative dementia, occurring in up to 15–20 percent of patients. NCDLB has an insidious onset with gradual progression. Typically, there is wide symptom fluctuation that can mimic delirium. A careful medical and neurological assessment of these episodes does not find a specific, acute etiology. In addition, patients with NCDLB exhibit recurrent formed visual hallucinations and spontaneous parkinsonian symptoms. REM sleep disorders, common in NCDLB, may precede the development of cognitive symptoms. In contrast to AD, memory impairment is less severe early in NCDLB and the cognitive fluctuations are more pronounced. Hallucinations appear earlier in the disease process in NCDLB than AD. Anxiety, depressive, and other neuropsychiatric symptoms are more common in NCDLB compared to AD. Other features of NCDLB include repeated falls, syncopal symptoms, unexplained loss of consciousness, and increased sensitivity to antipsychotic medications. Due to increased sensitivity to extrapyramidal side effects and falls, antipsychotics should be avoided if possible in patients with NCDLB.
Frontotemporal Neurocognitive Disorder (FTNCD)
FTNCD is a group of neurodegenerative dementias characterized by localized atrophy of frontal and/or temporal lobes. Symptoms usually begin in the forty-five to sixty-five years of age range and gradually progress from mild to severe. There are two different subtypes of FTNCD: (1) the frontal (behavioral) variant and (2) the language variant (primary progressive aphasia). In the frontal variant, behavioral symptoms predominate. These behaviors can range from apathy and social withdrawal to increased impulsivity, irritability, and disinhibited behaviors. Patients with the behavioral variant of FTNCD often demonstrate socially inappropriate, disinhibited behavior that commonly results in a psychiatric evaluation. Compared to AD, executive dysfunction is disproportionately affected early in the behavioral variant of FTNCD, while memory functions are relatively preserved until later stages of the illness. Decline in language ability is the early presenting symptom in the language variants of FTNCD. The language variant is subdivided into semantic, agrammatic/nonfluent, and logopenic variants, based on relative impairments in comprehension, fluency, and syntax. Behavioral symptoms are seen in the later stages of the language variant of FTNCD.
Neurocognitive Disorder Due to Traumatic Brain Injury
Traumatic brain injury (TBI) can lead to a NCD. TBI may cause posttraumatic amnesia, confusion, or loss of consciousness, as well as focal neurologic deficits. Inattentiveness, executive dysfunction, and personality changes may also be present. The severity of cognitive impairment due to TBI can range from mild to severe and cause disabling symptoms. NCD due to TBI may be transient or persistent, and varies depending on the severity of trauma, age, and other factors related to the individual or the nature of the trauma.
Neurocognitive Disorder Due to Prion Diseases
Protein-like infectious agents cause prion diseases. The transmission of prion diseases via body fluids is well documented. However, sporadic and familial cases are known to occur. Multiple prion diseases have been described, with Creutzfeldt-Jakob disease (CJD) being the most common. CJD typically presents with rapidly progressing cognitive decline often accompanied by gait abnormalities, myoclonus, and seizures. As a group, these diseases tend to be rapidly progressive and fatal within several months.
Neurocognitive Disorder Due to HIV Infection
The prevalence and severity of cognitive symptoms increase in the later stages of HIV disease. A syndrome of mild NCD due to HIV disease (also called minor motor/cognitive disorder) includes mental slowing, impaired attention and memory, slowed movements, incoordination, and mood and personality changes. Late-stage HIV disease and AIDS can also cause major NCD. In HIV dementia (major NCD), MRI of the brain shows increased hyperintensities on T2 weighted images in subcortical gray and white matter. It is important to rule out opportunistic infections (e.g., herpes simplex encephalitis, progressive multifocal leukoencephalopathy, and toxoplasmosis) and primary or secondary malignancies or stroke, which may cause cognitive symptoms in patients with AIDS, before making a diagnosis of NCD due to HIV.
Neurocognitive Disorder Due to Parkinson’s Disease
Mild NCD is common in Parkinson’s disease, and in 20–40 percent of patients, the cognitive symptoms progress to major NCD. Spontaneous parkinsonian symptoms may be seen in NCDLB, FTNCD, and some cases of AD. The onset of parkinsonian symptoms relative to cognitive symptoms helps inform the etiology of the dementia diagnosis. Major NCD due to Parkinson’s disease is characterized by the presence of parkinsonian motor symptoms preceding the onset of the cognitive symptoms by at least one year. However, the development of cognitive impairment prior to the onset of parkinsonian symptoms raises the possibility of other NCD diagnostic considerations, particularly NCDLB.
Neurocognitive Disorder Due to Huntington’s Disease
Huntington’s disease (HD) is caused by CAG trinucleotide expansion. Although motor symptoms are often the hallmark of HD, mood, psychotic, and cognitive symptoms are also common. Cognitive symptoms are mild at first but are often progressive. Advancing disease is characterized by progressive motor and cognitive symptoms leading to profound disabilities, ultimately resulting in death.
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