A 50-year-old man presents with progressive asymmetric muscle weakness, fasciculations in the arms, and spasticity in the legs over 18 months. Sensory examination is normal. He dies of respiratory failure. Autopsy would most likely show degeneration of which structure?

• A Anterior horn cells and lateral corticospinal tracts ✓
• B Caudate nucleus and putamen
• C Substantia nigra pars compacta
• D Posterior columns only

Explanation

This describes amyotrophic lateral sclerosis (ALS), the most common motor neuron disease. ALS uniquely involves both upper motor neurons (lateral corticospinal tract degeneration causing spasticity) and lower motor neurons (anterior horn cell loss causing weakness and fasciculations). The combination with preserved sensation is characteristic. Substantia nigra degeneration is seen in Parkinson's disease. Caudate atrophy is seen in Huntington's disease. Posterior column degeneration is seen in neurosyphilis and B12 deficiency.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.