In writing An Atlas of Parkinson’s Disease and
Related Disorders, I have been conscious of the
need to find an appropriate match between the
text and the illustrative material. The text is
designed to provide a basic overview of the conditions
discussed, inevitably concentrating on those
areas which lend themselves best to photographic
illustration. Some movement disorders, by their
very nature, do not lend themselves to still
photography whereas others, characterized by
sustained postures, are ideally suited to the technique.
The field of movement disorders is relatively broad, encompassing disorders of increased
movement, such as tremors, dystonia, and tics, to disorders characterized by a
paucity of movement, such as Parkinson’s disease. Our understanding of the pathogenic
mechanisms and our treatment options are expanding at a rapid pace. This expansion
ranges from the medical and surgical advances in treating Parkinson’s disease to the flood
of genetic abnormalities that have now been found to cause various movement disorders.
The neurons of the corpus striatum receive an excitatory input from the cerebral cortex and the thalamus.
The major outputs project to the globus pallidus and the substantia nigra pars reticula (SNr), and use
gamma-aminobutyric acid (GABA) as a transmitter. Major efferent pathways from the globus pallidus
interna and the SNr project to the thalamus. Feedback to the striatum is through the dopaminergic
striatonigral pathway originating in the substantia nigra pars compacta (SNc; Figure 1).
These separate pathways utilize different neuropeptides and dopamine receptors.
Parkinsonism and Freezing Gait
Parkinson's disease (Chap. 366) is common, affecting 1% of the population 55. The stooped posture and shuffling gait are characteristic and distinctive features. Patients sometimes accelerate (festinate) with walking or display retropulsion. There may be difficulty with gait initiation (freezing) and a tendency to turn en bloc. Imbalance and falls may develop as the disease progresses over years.