Oral therapies for Parkinson's are temporary because, among other things, Parkinson's disease is a progressive neurodegenerative disease. Over time, the progressive loss of dopamine-producing neurons in the brain causes symptoms to worsen. The effects of oral medications, such as levodopa, can be well controlled in the early stages of the disease. However, many patients develop fluctuations in medication efficacy over time, known as the "on-off phenomenon." These fluctuations can significantly affect quality of life and lead to unpredictable fluctuations in movement abilities.