Sections of the spinal cord (at levels C.5 and Th.7) from a case of progressive muscular atrophy (amyotrophic lateral sclerosis) showing degeneration of the pyramidal tracts. This disease also affects the motor cells in the anterior horns − many of which degenerate and disappear. In other words, there is a combined degeneration of upper and lower motor neurons. The patient at first shows a progressive spastic weakness of the lower limbs, associated with a gross wasting of the muscles (due to the lower motor neuron lesion). Later on, this wasting is often best seen in the upper limbs. The wasted muscles show peculiar irregular twitches (fasciculation). There is no sensory loss in this condition. Note the dark staining of the posterior columns of the spinal cord; this is a characteristic appearance in cases of progressive muscular atrophy, and the reason for it is not clear.

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