Parkinson Disease
Most cases of Parkinson disease (PD) are sporadic. This syndrome
covers several diseases of different etiologies which affect primarily the
pigmented neuronal groups including the substantia nigra, locus
ceruleus, dorsal motor nucleus of cranial nerve X and the substantia
innominata. Patients usually present with movement problems such as
a festinating gait, cogwheel rigidity of the limbs, poverty of voluntary
movement, and a pill rolling type of tremor at rest. In time the patient's
facies will become mask-like. Usually mental deterioration does not
occur but some patients may become demented as the disease
progresses. Idiopathic PD commonly begins in late middle age and the
course is slowly progressive. The pigmented neurons are slowly lost as
the disease progresses and melanin pigment can be seen within the
background neuropil or within macrophages. Astrocytosis occurs
secondary to neuronal loss. (Hughes et al, 1993) (Takahashi and
Wakabayashi, 2001) (Eriksen et al, 2005)
Some patients with Parkinsonian symptoms also have dementia, and in
these patients there are Lewy bodies in the cerebral cortex, as well as
the substantia nigra. This can be termed Lewy body dementia, and it is
in the differential diagnosis for Alzheimer disease. Pathologically, Lewy
bodies in association with Parkinson disease are found within the
cytoplasm of pigmented neurons. For a diagnosis of Lewy body
dementia, the Lewy bodies must be found in the neocortex. These are
homogeneous pink bodies on H&E stains with a surrounding halo.
Immunohistochemical staining with antibody to alpha-synuclein is
positive in these Lewy bodies. (Kosaka, 2000)
There are genetic markers for PD. Mutations in the PARK2 gene
encoding for the protein parkin have been identified in some rare
familial forms of PD. An autosomal dominant form with mutations in the
alpha-synuclein gene has also been described. Additional genes with
mutations associated with PD include DJ1 and PINK1. (Eriksen et al,
2005)