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Clinical hallmarks of Parkinsons Disease
What are the clinical and pathologic hallmarks of Parkinsons Disease?
Patients with Parkinsons Disease may have several combinations of parkinsonian symptoms.
Typically, the onset is insidious in the sixth decade of life, and the symptoms usually begin unilaterally or predominate on one side of the body.
It is possible to recognize two clinical types of Parkinsons Disease: a tremor-dominant form with earlier age of onset, slower progression, and relatively preserved cognition and a postural instability and gait difficulty form with more bradykinesia, more rapid progression, and dementia.
Furthermore, Essential Tremor is more likely to coexist in the tremor-dominant form. Pathologically, there is loss of dopaminergic neurons in the SNc, and the surviving neurons contain Lewy bodies.
Although to a lesser degree than the SNc, other pigmented nuclei of the brain stem, such as the locus ceruleus and tegmental ventral area, are also involved by a similar process.
A recent clinicopathologic study showed that the presence of a resting tremor is more likely to be associated with Lewy bodies at autopsy.
Lewy bodies have also been demonstrated in nondopaminergic nuclei of the brain stem, the olfactory system, and the spinal cord.
This distribution of Lewy bodies appears to correlate with the nonmotor, “preclinical” manifestations of Parkinsons Disease.
In addition to a deficiency of dopamine, nondopaminergic abnormalities are increasingly recognized in Parkinsons Disease.
These nondopaminergic abnormalities may be responsible for some of the symptoms that are resistant to dopaminergic therapy such as freezing, depression, cognitive decline, and dysautonomia.
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