A 36-year-old man who had been healthy all his life now has progressive, symmetric muscular weakness. A year ago, he noted weakness in the area of the head and neck, which caused difficulty with speech, eye movements, and swallowing. In the past year, the weakness in the upper and lower extremities has increased, and he can no longer stand, walk, or feed himself. His mental function remains intact. Which of the following cells is most likely being destroyed in this man?
The progressive and symmetric nature of this patient's disease is a classic feature of amyotrophic lateral sclerosis (ALS). The muscles show a denervation type of grouped atrophy from the loss of lower motor neurons in anterior horns of the spinal cord. The "bulbar" form of ALS affects mainly cranial nerve nuclei and has a more aggressive course. Cortical upper motor neurons may also be lost, but the mental function is preserved in ALS. Ependymal cells line ventricles, which are normal in ALS. Microglial cells have a macrophage-like function and may be involved in demyelinating plaques of multiple sclerosis that can produce various motor signs and symptoms over time, but symmetry is not a feature of this disease. Oligodendrocytes provide myelin to axons in the CNS. Parkinson's disease with loss of substantia nigra pigmented neurons is characterized by rigidity and involuntary movements, not by muscular weakness. Huntington disease with loss of spiny neurons in the caudate nucleus causes abnormal movements, not weakness, and there can be associated dementia over time.
Ependymal cell
Lower motor neuron
Microglial cell
Oligodendrocyte
Central Nervous System