Major strokes are caused by a blockage of large or medium-sized arteries: the “pipes” through which blood flows. Arteries harden in older people, especially if they have diabetes, high blood pressure, high cholesterol, or have smoked. If a large or medium-sized artery closes and if there are no arteries in the neighborhood that can replace it, the region of the brain the artery supplies is infarcted, meaning it dies.
Unlike in PD where symptoms appear gradually and progress slowly over years, stroke symptoms appear suddenly and do not progress. The onset of PD is not dramatic; a selected group of neurons gradually die. A stroke is like a hurricane blowing away your house, while PD is more like a slow, steady rain eroding your basement.
Knowing the terminology used with strokes can be helpful. Atherosclerosis is the narrowing of a large artery by cholesterol. Low cholesterol diets, the use of “statins” (drugs that lower cholesterol), exercise, anti-hypertensive drugs, and cessation of smoking are factors in fighting atherosclerosis. Arteriosclerosis is the narrowing of medium and small-sized arteries by cho-lesterol and by changes in the artery’s muscular wall.
The same factors that fight atherosclerosis will like-wise fight arteriosclerosis. Hypertension (high blood pressure) contributes to and promotes both atherosclerosis and arteriosclerosis. Hypertension also results in the closure of tiny arteries, called arterioles. Such closure results in small infarctions known as lacunes, which individually cause no symptoms, but cumulatively may cause a variety of symptoms that mimic PD, especially when the lacunes occur in the basal ganglia.
A single stroke does not cause PD. However, multiple “silent” or “minor” strokes affecting the striatum, globus pallidus, thalamus, cerebellum, and midbrain— regions that regulate balance, movement and walking—may have a cumulative effect over several months or years that cause symptoms similar to PD. This condition is called vascular Parkinson, but the symptoms of vascular Parkinson usually do not respond to PD drugs. The treatment goal of vascular Parkinson is to prevent additional strokes. The course of the disease can be favorably altered by paying close attention to the factors that cause stroke.
Usually a neurologist or a PD expert can separate the effects of multiple minor strokes from those of PD, and those strokes can usually be seen on an MRI (magnetic resonance imaging) scan. Sometimes strokes and PD coexist; having PD does not protect you from having strokes, and vice-versa. How many of your symptoms are caused by stroke and how many by PD is likely some-thing only a specialist trained in PD can determine.