Parkinsons disease is notorious for so-called motor symptoms like muscle rigidity, tremor, slowed movement, and unsteady posture and gait. Less well known — even to some doctors who treat the disease — are the effects of Parkinson’s on thinking. These “cognitive” signs include a general slowness of thought, “tip of the tongue” forgetfulness of words, and difficulty juggling multiple mental tasks.
Parkinson’s disease and the medications used to treat it may also affect how the brain learns. And even stranger, certain Parkinson’s drugs can trigger compulsive behaviors such as pathological gambling or uncontrolled shopping. Understanding these and other aspects of how Parkinson’s disease affects the mind offers hope of a better life for people with a disease estimated to affect more than a half million Americans.
Parkinson’s is caused by the death of brain cells that producedopamine, one of the chemicals that carry messages between neurons. Low dopamine impairs the basal ganglia, which are brain regions that control movement and coordination.
Drug treatments try to shore up dopamine levels. For example, medications containing the chemical L-dopa provide extra raw materials to produce natural dopamine. Another, newer class of drugs, dopamine “agonists,” mimic the action of natural dopamine on motor-control brain cells.
Dopamine-boosting drugs address motor symptoms, and this allows people to function better. But realization is growing that some patients need help with non-motor symptoms. These include depression, anxiety, daytime sleepiness, insomnia, lightheadedness, urinary incontinence, nerve pain and loss of smell. Some patients develop memory loss and dementia, generally late in the disease’s progression.
In 2001 and again in 2006, the National Institute of Neurological Disorders and Stroke (NINDS) held meetings at which scientists, doctors, and patients discussed priorities in Parkinson’s disease research. Non-motor symptoms emerged as a major concern.
“In both summits, patient advocates and the clinical community identified it as one of the most important under-addressed areas for patients with Parkinson’s disease,” notes neurologist Debra Babcock, MD. She heads the NINDS program on Cognitive Neuroscience that funds research on non-motor Parkinson’s symptoms. “What’s worse is that some non-motor symptoms are actually aggravated by the treatments used for the motor symptoms.”
Nirenberg is an expert in impulse-control disorders associated with Parkinson’s medications. One factor that still obscures this problem even from experienced neurologists is the sensitive nature of the behaviors.
Some patients might be willing to bring up the fact that they have been eating uncontrollably. But it’s harder to uncover repeated and financially disastrous trips to the casino, or all-night Internet pornography-viewing sessions and visits to prostitutes.
A frank discussion with a spouse or partner can help. Then the medications can be changed to reduce or eliminate the problem