Currently in the United States, there are over 1.5 million people living with Parkinson's and 50,000 new cases reported each year. Worldwide more than 6 million people are affected with Parkinson's disease. The disease onset most frequently occurs between 50 and 65 years of age. The disease is a progressive neurodegenerative disorder that affects the motor system and is characterized by the symptoms of tremor, bradykinesia (slowed movement and hesitations), and rigidity (stiff joints). While many treatment interventions focus on movement symptoms in the upper extremity, Parkinson's disease can also affect gait and balance, speech, olfaction (sense of smell), sleep, and cognition.
Imagine trying to move your fingers to turn the pages of a book, but instead of being able to complete that relatively simple task your fingers suddenly get stuck and refuse to respond to your brain's command to move. After several seconds of hesitation your fingers unlock and you can turn the page, however this muscle "freezing" happens periodically during activities of daily living such as trying to tie your shoes, eat, or walk. This freezing and hesitation of movement is known as "bradykinesia", a motor symptom that is a major source of functional impairment for Parkinson's patients. As if it's not enough that you periodically get stuck moving, the disease now decides to cause your hands to shake uncontrollably while you are trying to write, type, or simply relax and watch television. This uncontrollable shaking, or tremor, is often the most visible sign of Parkinson's. As you continue your day, you now notice some joints are stiffer than normal and it is difficult to move them. This is referred to as rigidity, another motor symptom of Parkinson's disease, which occurs when antagonistic muscles controlling a joint (such as the biceps and triceps at the elbow) are both receiving high levels of involuntary activation. Patients affected by this movement disorder may encounter different levels of tremor, bradykinesia and rigidity throughout the day as the patient fluctuates between motor symptoms of too much involuntary movement or limited control over desired movements. In addition, dyskinesias or wild involuntary movements can develop as a motor side effect of drug therapy.
The current clinical standard in evaluating symptoms is the Unified Parkinson's Disease Rating Scale (UPDRS), a qualitative ranking system developed by a panel of movement disorder experts. The UPDRS includes multiple sections to monitor several areas of disease impact including motor and non-motor experiences of daily living, a motor examination, and motor complications. The motor examination section includes several movements the patient completes to elicit motor symptoms while a clinician qualitatively assesses the symptoms through visual examination and assigns a 0 – 4 score. The UPDRS exam is normally completed during an office visit in the presence of a trained clinician. In addition to the UDPRS, clinicians may ask patients to keep home journals to record when they took medication and symptom severities at various times during the day. Capturing this information is important because motor symptoms and side effects fluctuate during the day based on timing and dose of medications.
Parkinson's disease is caused by a loss of dopamine-producing neurons in the substantia nigra region of the brain. While the exact reason for this neuron death remains unknown, significant strides have been made in the treatment of motor symptoms. Pharmaceutical interventions such as Levodopa are typically prescribed when patients are first diagnosed to treat motor symptoms. However, over time, dyskinesias or wild involuntary movements as a side effect of drug therapy can develop as a motor complication. In addition to pharmaceuticals targeted to treat motor symptoms, new drug development is now focusing on neuroprotective strategies to slow or stop the progression of the disease. Another treatment option, deep brain stimulation, improves motor symptoms and reduces motor fluctuations and dyskinesia in patients whose symptoms cannot be managed with medications. The efficacy of these treatment interventions is often judged by alleviation of patient symptoms and improving quality of life.