Question 221

Question:

A 50-year-old man has had gradually progressive weakness of the hands during the past year. Physical examination shows atrophy of the forearm muscles, fasciculations of the muscles of the chest and upper extremities, and hyperreflexia of the lower extremities. A Babinski sign is present bilaterally. Sensation is intact. Which of the following is the most likely diagnosis?

Correct Answer: A.  Amyotrophic lateral sclerosis

This patient is exhibiting signs of upper and lower motor neuron degeneration, suggesting a diagnosis of amyotrophic lateral sclerosis (ALS). Upper motor neuron degenerative signs include hyperreflexia, increased tone, and positive bilateral Babinski signs. Lower motor neuron degenerative signs include muscle atrophy, areflexia, fasciculations, and flaccid paralysis. Since ALS causes degeneration of both upper and motor neurons, this is the likely diagnosis for this patient.
Alzheimer dementia is not known to correlate with motor neuron loss. Guillan-Barre is usually post-viral illness of the GI tract and usually presents with a rapidly ascending, reversible muscle paralysis. Multiple cerebral infarcts would explain the upper motor signs but not the degeneration of lower motor neurons. Multiple sclerosis usually presents in middle-aged women with optic signs or singular neurologic defects that include peripheral sensory losses, not the universal loss of motor neurons described above.