Question

Which of the following represents the site of the lesion in Motor Neuron disease?

• A. Anterior horn cells
• B. Peripheral nerve
• C. Spinothalamic tract
• D. Spinocerebellar tract

Hint:

Lower motor neuron cell bodies live in the anterior horn.

Answer 1

The Correct Option is A

Step 1: Define the disease. Motor Neuron Disease (MND), most commonly amyotrophic lateral sclerosis, is a degeneration of motor neurons. It affects both upper motor neurons (in the motor cortex and corticospinal tract) and lower motor neurons.
Step 2: Locate the lower motor neurons. The cell bodies of the lower motor neurons sit in the anterior (ventral) horn of the spinal cord. Their degeneration produces wasting, fasciculations and weakness. Among the options, the anterior horn cells are the spinal site of MND.
Step 3: Note what is spared. A key feature of MND is that the sensory pathways are spared. There is no sensory loss.
Step 4: Exclude the distractors. The peripheral nerve is affected in peripheral neuropathies, not primarily in MND. The spinothalamic tract carries pain and temperature (a sensory pathway) and is spared. The spinocerebellar tract carries unconscious proprioception (also sensory) and is spared.
Conclusion: The lesion sits in the anterior horn cells, option A.