A rupture or an occlusion in one of the multitude of tiny blood vessels at the base of the brain or, more properly, at the juncture between the brain and the spinal cord usually causes the locked-in syndrome. But vascular accidents in other parts of the brain, tumors, encephalitis, and brain injuries localized in the ventral midbrain can also result in the locked-in syndrome. Other, less frequent, causes of total motor paralysis are degenerative neuromuscular diseases, the most frequent of these being amyotrophic lateral sclerosis (ALS), which involves a continuously progressive degeneration of the nerves that activate muscles all over the body. In ALS, the weakness most often begins in the lower extremities and then moves on to the hands and arms, finally paralyzing the facial muscles, and the muscles involved in swallowing and breathing. During the terminal stage, patients with ALS can stay alive only with artificial feeding and ventilation.
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