Alzheimer disease (AD) is the most common form of dementia.[1, 2] AD
is a progressive degenerative disease of the brain, strongly associated
with advanced age. However, it should not be considered a part of the
normal aging process. AD is characterized by a relentless progression of
symptoms associated with defined neurological changes.
The neuropathology of AD in persons with trisomy 21, or Down syndrome (DS), closely resembles that of AD in persons without DS.[3, 4, 5, 6, 7] Autopsy studies in persons with DS showed that almost all had brain lesions meeting the criteria for AD.[8, 9] As has been observed in persons without DS, autopsies of patients with DS showed intraneural neurofibrillary tangles, extracellular neuritic plaques, amyloid angiopathy, and deposits of amyloid beta (Abeta) protein in senile plaques.[8, 10] In persons with DS, the Abeta deposits can be seen in the cerebral cortex as early as in their 30s.[11, 12]
However, because these changes are superimposed on individuals that already have a reduced brain volume, especially in the hippocampus, and other developmental abnormalities, such as reduced dendritic arborizations, decreased number of spines, spine atrophy, and abnormalities of spine orientation in pyramidal neurons, this form of AD is not an exact biologic model or a replica of the AD seen in persons without DS. Even though conclusions from research studies may be interchangeable, AD in persons with DS should be considered a different entity from AD in persons without DS.
Individuals with DS develop a clinical syndrome of dementia with clinical and neuropathologic characteristics almost identical to those of AD as described in individuals without DS. However, clinical differences have been observed, the main one being the early age of onset of AD in individuals with DS. These patients present with clinical symptoms in their late 40s or early 50s.[13, 14, 3, 15, 16] Other studies have also shown some clinical differences that might be unique to persons with DS.
One study that compared the clinical findings in persons with dementia and DS with clinical findings in persons with dementia and intellectual disabilities due to other etiologies found that patients with DS had a higher prevalence of mood changes, overactivity, auditory hallucinations, and disturbed sleep, as well as less aggression.[17, 18, 19]
Temple and Konstantareas found that persons with DS and AD have less severe psychotic behaviors, fewer hallucinations, and fewer delusions and were more likely to engage in physical movements than those with AD only. In this study, 66% of the persons with AD and no DS were taking rivastigmine or donepezil, and only 26% of persons with AD and DS were on those medications. The differences observed might have been related more to the use of the medications than to the disease itself.[20]
Because no treatment is available for the primary disease, prognosis is poor. AD is responsible for the sharp decline in survival in persons with DS older than 45 years. Only about 25% of persons with DS live more than 60 years, and most of those have AD.
The neuropathology of AD in persons with trisomy 21, or Down syndrome (DS), closely resembles that of AD in persons without DS.[3, 4, 5, 6, 7] Autopsy studies in persons with DS showed that almost all had brain lesions meeting the criteria for AD.[8, 9] As has been observed in persons without DS, autopsies of patients with DS showed intraneural neurofibrillary tangles, extracellular neuritic plaques, amyloid angiopathy, and deposits of amyloid beta (Abeta) protein in senile plaques.[8, 10] In persons with DS, the Abeta deposits can be seen in the cerebral cortex as early as in their 30s.[11, 12]
However, because these changes are superimposed on individuals that already have a reduced brain volume, especially in the hippocampus, and other developmental abnormalities, such as reduced dendritic arborizations, decreased number of spines, spine atrophy, and abnormalities of spine orientation in pyramidal neurons, this form of AD is not an exact biologic model or a replica of the AD seen in persons without DS. Even though conclusions from research studies may be interchangeable, AD in persons with DS should be considered a different entity from AD in persons without DS.
Individuals with DS develop a clinical syndrome of dementia with clinical and neuropathologic characteristics almost identical to those of AD as described in individuals without DS. However, clinical differences have been observed, the main one being the early age of onset of AD in individuals with DS. These patients present with clinical symptoms in their late 40s or early 50s.[13, 14, 3, 15, 16] Other studies have also shown some clinical differences that might be unique to persons with DS.
One study that compared the clinical findings in persons with dementia and DS with clinical findings in persons with dementia and intellectual disabilities due to other etiologies found that patients with DS had a higher prevalence of mood changes, overactivity, auditory hallucinations, and disturbed sleep, as well as less aggression.[17, 18, 19]
Temple and Konstantareas found that persons with DS and AD have less severe psychotic behaviors, fewer hallucinations, and fewer delusions and were more likely to engage in physical movements than those with AD only. In this study, 66% of the persons with AD and no DS were taking rivastigmine or donepezil, and only 26% of persons with AD and DS were on those medications. The differences observed might have been related more to the use of the medications than to the disease itself.[20]
Because no treatment is available for the primary disease, prognosis is poor. AD is responsible for the sharp decline in survival in persons with DS older than 45 years. Only about 25% of persons with DS live more than 60 years, and most of those have AD.
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