Frequency, Lifespan, and Co-Morbidity

Diseases of the basal ganglia are essentially characterized by abnormal motor activity. Based on the type of motor problem, diseases of the basal ganglia can be classified into hypokinetic or hyperkinetic groups. Hypokinetic basal ganglia disorders include PD, in which the amplitude and velocity of voluntary movements are diminished or, in extreme cases, non-existent. 

Found at the other end of the spectrum are the hyperkinetic basal ganglia disorders, which are represented by HD and essential tremor. In these two conditions, excessive abnormal movements such as chorea or tremor are superimposed onto and interfere with normal voluntary movements. Although hyperkinetic basal ganglia disorders are probably as diverse as hypokinetic basal ganglia disorders, their specific disease markers such as gene mutations, which exist for several of the hyperkinetic syndromes create more accurate, less problematic, classifications. 

Among the neurodegenerative diseases predominantly affecting the spinal cord are ALS and spinal muscular atrophy, in which the most severe lesions are found in the anterior part of the spinal cord, and the already cited Friedreich ataxia. 

---