Parkinson's disease. Coloured Computed Tomography (CT) scan of the brain of a patient suffering from Parkinson's disease. This is a horizontal slice through the brain. Cerebral hemispheres are green; the skull is pink; fluid-filled ventricles are blue (at centre). Parkinson's disease has caused the ventricles to increase in size as brain tissue loses density, with death of cerebral tissue. Parkinson's disease is caused by deterioration in clusters of brain cells called the basal ganglia, which help to control muscle movement. Symptoms of the disease include tremor, joint rigidity, & slow movement. The disease progresses over 10-15 years to severe weakness and incapacity.