In the psychiatric nomenclature, the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (American Psychiatric Association, 2013) issued a new classification system for the diagnosis of AD and other dementias. The DSM-5 is widely used by psychiatrists and other mental health practitioners and is mapped to the International Classification of Diseases (ICD) codes that are widely used by insurance companies. In the DSM- 5, the conditions that were previously referred to collectively as dementias are now termed neurocognitive disorders (NCDs) to distinguish diseases such as AD from psychiatric disorders that have cognitive impairment as a symptom rather than a defining feature. Although the American Psychiatric Association acknowledges that the term dementia is acceptable and likely will continue to be widely used in clinical practice, the usage of the new diagnostic term is intended to encourage identification of the etiology or origin of the cognitive decline. Specific subtypes of NCDs are further noted in the DSM-5 (e.g., AD, frontotemporal lobar degeneration, LBD, vascular disease). In addition, the DSM-5 recognizes that symptoms range along a spectrum from major to minor. Criteria for the diagnosis of major NCD due to AD are met when NCD (dementia) is present, there is a gradual progression of impairment, and AD is determined to be probable based on: 1. Evidence of an Alzheimer’s genetic mutation from family history or testing. 2. The presence of the following three elements: a. Clear evidence of decline in memory and learning and in at least one other neuro-cognitive domain: complex attention, executive function, language, perceptual motor, or social cognition (from detailed history or multiple neuropsychological testing). b. Progressive cognitive decline. c. An absence of evidence of mixed etiology. The diagnosis of mild, or “minor” NCD due to AD is made using the same criteria as those used for major NCD due to AD, except that memory and learning represent the only impaired neurocognitive domain. For minor NCD due to AD, the absence of a genetic mutation changes the diagnosis of AD from probable to possible. ● Laboratory blood tests: Typically include a complete blood count, serum electrolyte levels, chemistry and thyroid panels, glucose levels, liver function studies that include blood urea nitrogen and creatinine levels, vitamin B 12 and folate studies, erythrocyte sedimentation rate, and drug (e.g., digoxin) levels. These tests are conducted to assess potential causes of reversible conditions. ● Neuroimaging : Such as a computed tomography (CT) scan or MRI, rules out strokes or tumors and can reveal changes in the brain’s structure and function that may suggest a specific dementia diagnosis. PET imaging reflects the brain’s metabolic activity, and in patients with AD, the temporal and parietal lobes may exhibit diminished activity. Single photon emission computed tomography (SPECT) and electroencephalography (EEG) may also be used. ● Neuropsychological testing : Includes measures of intelligence, memory, language, executive function, visuo-perceptual skills, and other abilities related to brain functioning. A comprehensive neuropsychological assessment involves multiple tests over several hours. During an initial workup with a physician, screening tools are used to indicate the need for further testing; these screening tools do not diagnose dementia, but identify the need for further workup. The most commonly performed screening tests are the Mini-Mental State Examination (MMSE), the Mini- Cog Assessment, and the Montreal Cognitive Assessment (MoCA). These screening tools are briefly reviewed next and positive findings would ideally lead to more extensive
(i.e., anatomical, biochemical, and physiological measures). The preclinical criteria are useful for research purposes only and additional research is needed to better understand biomarkers and the progression of AD. The criteria were developed to be flexible for use in general practice without immediate access to neuropsychological testing, advanced imaging, or other lab testing used in the diagnosis of dementia. The guidelines include core clinical criteria that are useful in all clinical settings for the diagnosis of dementia, ranging from the mildest to the most severe stages, and for diagnosing probable and possible AD dementia. The core clinical criteria for dementia include: 1. Interference with vocational or routine activities. 2. Decline from previous levels of functioning. 3. Cognitive impairment that is detected via input from the person and an informed other, and an objective cognitive assessment – neuropsychological testing need only be performed if diagnostically warranted. 4. Cognitive or behavioral impairment involving two or more of the following domains: a. Impaired ability to acquire or remember new information. b. Impaired reasoning and handling of complex tasks, or poor judgment. c. Impaired visuospatial abilities. d. Impaired language functions. e. Changes in personality, behavior, or comportment. (McKhann et al., 2011) The core clinical criteria for probable AD include all of the core clinical criteria for dementia previously noted, along with: 1. Insidious onset. 2. Evidential history of worsening cognition. 3. Initial and most prominent cognitive deficits present in history and examination in one of the following categories: a. Amnestic symptoms, including impairment in learning and recall of recent information. b. Nonamnestic symptoms involving language, visuospatial cognition, or executive dysfunction. 4. No evidence of cerebrovascular disease, features of either FTD or LBD, features of progressive aphasia or neurological disease, or a non-neurological comorbidity or medication that could affect cognition. (McKhann et al., 2011) Elements of diagnostic workup Individuals who experience disconcerting memory and cognitive issues should have a comprehensive diagnostic workup from their primary care physician, a neurologist, or a gerontologist. The diagnostic evaluation for a person suspected of having AD will include the following elements: ● A complete patient history: Including a detailed description of what memory or cognitive issues are present and how and when these symptoms developed, should be obtained. A pertinent medical history should also be obtained, including a review of such risk factors as history of head trauma and/or neurological or cardiovascular conditions. Current prescription and over-the-counter medications should be scrutinized. ● A physical examination : Should include vital signs assessment (to rule out orthostatic hypotension and cardiac irregularities), comprehensive neurological screening, and hearing and vision screens (individuals who do not hear or see well can seem confused and forgetful). ● A psychosocial assessment : Should investigate the patient’s emotional state, including screening for depression (depression can cause pseudo-dementia). ● An environmental assessment : Should evaluate the patient’s living environment. Ideally, information regarding the patient’s psychosocial status and living environment (including behavioral issues and safety concerns) should be corroborated with others because cognitive impairment can preclude effective and accurate communication between a patient and a healthcare provider.
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