Primary Lateral Sclerosis (PLS) is a rare neurological disorder that affects the upper motor neurons in the brain and spinal cord. It leads to progressive muscle weakness and stiffness, primarily impacting voluntary movements. Symptoms often include difficulty walking, muscle cramps, and speech problems, which can gradually worsen over time. PLS is considered a type of motor neuron disease, but it differs from other conditions like Amyotrophic Lateral Sclerosis (ALS) because it does not typically affect lower motor neurons. The exact cause of PLS is unknown, and there is currently no cure, though treatments focus on managing symptoms and improving quality of life.