I. General Principles
Degenerative diseases are characterized by progressive neuronal degeneration and loss in disease-specific regions. The disease arises without any clear inciting event in a patient without previous associated neurologic deficits. In most disorders, the etiology is unknown. The most common manifestations involve at least one of the following: dementia, movement disorders, weakness or sensory loss due to spinal cord involvement. Dementia may be caused by a degenerative disease, or may be caused by multiple small infarcts (vascular dementia) or other disorders. Part A covers disorders characterized primarily by dementia (primary cortical involvement) and Part B covers disorders involving primarily the basal ganglia and/or spinal cord.
A. Clinical Signs
1. Signs and Symptoms are predictable and dependent upon the area of the nervous system involved.
a. Cerebral Cortex ‑ degeneration (progressive loss of neurons and secondary white matter lesions) leads to dementia with impairment of intellectual function and judgement; memory loss is common.
b. Basal Ganglia ‑ lesions lead to a variety of movement disorders and sometimes to "subcortical dementia"
c. Spinal Cord ‑ degeneration of corticospinal tract causes weakness and spasticity; lesions in posterior columns cause loss of position sense; loss of motor neurons (anterior horn and motor cranial nerve nuclei cells) cause weakness and flaccidity.
2. Some of the disorders have an hereditary pattern and family history can be used for screening.