ALS involves degeneration of which neurons?

• A. Anterior horn cells
• B. Upper motor neurons in the corticospinal tract
• C. Visual cortex neurons
• D. Cerebellar Purkinje cells

Answer: (A)

ALS is a motor neuron disease, so the key problem is degeneration of the neurons that control voluntary muscle movement. The most direct match here is the loss of lower motor neurons located in the anterior horn of the spinal cord and the brainstem motor nuclei. When these anterior horn cells die, you get classic LMN signs—muscle weakness, atrophy, fasciculations, and hyporeflexia. Upper motor neurons in the corticospinal tract are also affected in ALS, contributing to spasticity and brisk reflexes, but the question points to the primary neuronal population involved, which are the anterior horn cells. Visual cortex neurons aren’t typically affected, so vision stays intact, and cerebellar Purkinje cells aren’t the usual players in ALS, which is why they don’t fit.