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Rationale for Thorough Screening and Evaluation |
When a patient declines in function, a thorough evaluation is necessary to
look for reversible causes or, if no reversible cause is found, to confirm
that the decline is consistent with Alzheimer's disease. Alzheimer's disease
is a diagnosis of exclusion in persons with Down syndrome, just as it is
in the general population. Traditional neuropsychological testing, used for
persons in the general population who are suspected of having Alzheimer's
disease, is less helpful for assessing persons with an intellectual disability,
and therefore, often is not helpful in making the diagnosis. Therefore, careful
clinical evaluation is necessary to avoid missing potentially reversible
causes of the decline. The medical history and physical exam provide insight
into the decline, evaluate for associated symptoms, and initiate the evaluation
for etiology. Vision and hearing evaluations are important because a loss
of sense can be very problematic for a person with an intellectual disability
who has limited reserve (i.e., limited cognitive function) with which to
compensate. Blood work should include thyroid function, vitamin B12, folic
acid, complete blood count (CBC), and chemistry profile. A computerized tomography
(CT) scan or magnetic resonance image (MRI) scan can evaluate for intracranial
lesions or atrophy. A lateral neck X-ray in neutral, flexion, and extension
is indicated to evaluate for atlanto-axial instability.
In addition, careful screening for psychological or social problems is a
critical part of the evaluation. Mental health disorders often present differently
in persons with Down syndrome and other disabilities because of cognitive
and expressive language limitations in this population. As a result, mental
health disorders may be difficult to distinguish clinically from Alzheimer's
dementia. For example, the following symptoms are common to both depression
and Alzheimer's disease in this population: loss of adaptive skills, disruption
of sleep cycle and appetite changes, apathy, moodiness, irritation, aggressiveness,
psychomotor agitation or retardation, memory loss, and the presence of psychotic
features (such as extreme withdrawal, delusions and an increase in hallucinatory-like
self-talk). Alzheimer's disease is particularly difficult to rule out because
there is no definitive test for this disorder. To further complicate matters,
depression may coexist with Alzheimer's disease. In this case, prompt treatment
of depression will preserve functioning for some time, even though a downhill
course may be inevitable.
Despite these difficulties, depression and other mental health disorders
have been diagnosed in previous case studies. These reports demonstrate that
diagnosis of mental health disorders is enhanced when behaviors, rather than
subjective feelings, are emphasized as criteria and when care is taken to
rule out all other sensory deficits and medical conditions such as Alzheimer's
disease or hypothyroidism. Additionally, results from previous case studies
suggest that the differential diagnosis of depression and Alzheimer's disease
is enhanced if close attention is paid to the symptom course. Depression
tends to show an up-and-down pattern of decline, which will show improvement
and an eventual return to premorbid states of functioning with time and treatment.
Symptoms of Alzheimer's disease tend to fluctuate up and down in the early
stages, but over time will show a progressive and nonreversible pattern of
decline.
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