Amyotrophic lateral sclerosis



Amyotrophic lateral sclerosis



Amyotrophic lateral sclerosis


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USMLE® Step 1 questions

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Amyotrophic lateral sclerosis

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USMLE® Step 1 style questions USMLE

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A 53-year-old male presents to his primary care physician with worsening hand and leg weakness. He often feels as if his left leg is “dragging” and experiences “spasms” while running. He additionally has difficulty holding a pen as firmly as he used to. Past medical history is notable for Graves disease. The patient does not smoke, use alcohol or other illicit substances. His temperature is 37.0°C (98.6°F), pulse is 65/min, respirations are 14/min, blood pressure is 125/64 mmHg, and O2 saturation is 98% on room air. Physical exam is notable for 4/5 strength in the right hand, with thenar muscle atrophy, as well as 4/5 strength in the left lower extremity. He has upgoing toes when the inner sole of the left foot is stroked. Which of the following best describes the pathophysiology of this disease? 

External References

First Aid








Amyotrophic lateral sclerosis (ALS)

spinal cord lesions p. 548


Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a neurodegenerative disease that affects both upper and lower motor neurons. Motor neurons reach from the brain to the spinal cord and from the spinal cord to muscles throughout the body. The progressive degeneration of these motor neurons leads to muscle weakness and atrophy.

ALS symptoms typically develop slowly over time. Early symptoms may include muscle weakness or stiffness, difficulty speaking, swallowing, or breathing. As the disease progresses, patients lose their ability to move and speak and eventually require total care. In some cases, people with ALS live for many years after diagnosis; however, most people with ALS die within a few years of diagnosis.


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