Parkinson’s disease usually is thought of as a movement disorder. People with Parkinson’s typically first develop a tremor in one hand, followed by slowed movement, stiffness and loss of balance. But within 10 years of diagnosis, more than three-quarters of Parkinson’s patients also develop cognitive problems such as difficulty with memory and with performing sequential tasks and following instructions. The movement problems have been traced back to degeneration of a neurological pathway that controls movement. The source of the cognitive problems is more puzzling.
Joel S. Perlmutter, MD, a professor of neurology at Washington University School of Medicine in St. Louis, has received a $3.2 million grant from the National Institute of Neurological Disorders and Stroke to investigate whether damage to motor pathways leads to brain inflammation and injury to the cerebral cortex. The cerebral cortex is the seat of higher-order thinking, so damage to the cerebral cortex might be linked to cognitive problems.
Perlmutter and colleagues also will assess whether an experimental drug that reverses damage to the motor pathway in animals also reduces dysfunction in the cortex.
The results of these studies are expected to lay the groundwork for clinical trials to assess whether the experimental drug synoxizyme reduces brain inflammation and cortical injury in people, thereby slowing, stopping or maybe even partially reversing motor or cognitive problems in people with Parkinson’s.
“We have lots of medicines to help reduce the motor symptoms but really almost nothing to help the cognitive problems,” said Perlmutter, who is also a professor of radiology, of neuroscience, of occupational therapy and of physical therapy. “That’s partly because we don’t know why it’s happening.”
Parkinson’s disease is caused by the degeneration of dopamine-releasing neurons in the nigrostriatal pathway deep within the brain. Replacing lost dopamine is the most common treatment for Parkinson’s. While drugs such as L-dopa reduce movement problems, they do nothing for cognitive symptoms.