What Is Motor Neuron Disease?
7. Primary Lateral Sclerosis
Primary lateral sclerosis (PLS) is a rare condition where there is neurodegeneration of the upper motor neurons (UMNs), leading to progressive spinobulbar spasticity. Since many cases that have been initially diagnosed as PLS will be reclassified as ALS once the disease has progressed, some experts have suggested a disease duration of a minimum of 3 years is required before diagnosis is rendered.
There are still those who debate if PLS is a distinct pathologic entity or if it represents another end of the ALS clinical spectrum. It tends to affect those over the age of 50 years old and progresses over several years or decades. Symptoms usually start in the legs, tongue, or hands, and can include difficulty with balance, stiffness, weakness, clumsiness, and spasticity.
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