Parkinson's disease. Computer artwork of neurones (nerve cells, blue) containing Lewy bodies (red). Lewy bodies, which are deposits of protein, are found in neurones from the brains of patients with Parkinson's disease. It is thought that they cause the progressive degeneration of the neurones that leads to the symptoms of Parkinson's. These symptoms include, tremor, muscular rigidity, poor balance and depression. Although drugs may alleviate the symptoms Parkinson's disease is ultimately fatal.