Dementia Due to Parkinson’s Disease
Although dementia rarely occurs as an initial
symptom of Par-kinson’s disease, it is found in nearly 40% of such patients
older than 70 years of age. Approximately 1 million people in the USA have the
disease, with 50 000 new cases being diagnosed each year. The prevalence for
persons over 60 is 1%. The disease re-sults from loss of dopamine production in
the basal ganglia, and can be idiopathic or postencephalitic. Usually the
patient is 50 years of age or older, and unlike Alzheimer’s and Pick’s demen-tias,
this disease occurs slightly more often in men (Berg et al., 1994). Dementia most commonly occurs in cases of
Parkinson’s disease in which the decline has been rapid and response to
anti-cholinergics has been poor.
The pathology of Parkinson’s disease involves
depigmen-tation of the so-called pigmented nuclei of the brain (locus coer-uleus, substantia nigra). These nuclei then contain eosinophilic Lewy bodies. As in Alzheimer’s disease
the cerebral cortex of many of these patients contains many senile plaques and
neurofi-brillary tangles, loss of neurons, and decreased concentrations of
choline acetyltransferase. Patients with parkinsonian dementia also have
reduced choline acetyltransferase in the cerebral cortex and substantia nigra.
The clinical features of Parkinson’s disease are
well described, with the cardinal triad being tremor, rigidity and
bradykinesia. Associated features include postural instability, a festinating
gait, micrographia, seborrhea, urinary changes, con-stipation, hypophonia and an
expressionless facial countenance. The tremor in Parkinson’s disease has a
regular rate and is most prominent when the patient is sitting with arms
supported; it has therefore been described as intention tremors. Paranoid
delusions and visual hallucinations may occur, but auditory hallucinations are
rare. Antipsychotics with low incidence of extrapyramidal symptoms such as
quetiapine, olanzepine, and ziprasidone are The pharmacological treatment of
Parkinson’s disease recommended. involves the use of a number of types of
medication and ziprasidone are recommended. These in-clude selegiline a
selective monoamine oxidase inhibitor, levo-dopa, other dopamine agonists
(pramipexole, bromocriptine, pergolide mesylate, amantadine), and various
anticholinergic agents (benztropine). Selegiline should not be given to
patients on antidepressant medication as there is a risk that dopaminergic
agents may activate psychosis or mania and that anticholinergic drugs may
increase confusion. When discontinuing levodopa after a long course of
treatment, the drug should be tapered so as to prevent a discontinuation
syndrome similar in nature to the neuroleptic malignant syndrome. Some
medications (metoclo-pramide, droperidol, several antipsychotics) may produce
par-kinsonian features such as masked facies, sparsity of speech and tremor,
and in those cases the appropriate course of treatment is to discontinue the
offending medication. Several researchers are looking into the possibility of
using embryonic stem cells implants as treatment for Parkinson’s disease and
several other conditions.
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