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Clinical features of amyotrophic lateral sclerosis and other forms of motor neuron disease

Lauren B Elman, MD
Leo McCluskey, MD, MBE
Section Editor
Jeremy M Shefner, MD, PhD
Deputy Editor
John F Dashe, MD, PhD


Amyotrophic lateral sclerosis (ALS), first described by Charcot in the nineteenth century, is a relentlessly progressive, presently incurable, neurodegenerative disorder that causes muscle weakness, disability, and eventually death. ALS is also known as Lou Gehrig's disease, after the famous New York Yankee baseball player who was affected with the disorder [1-3].

ALS has an annual incidence of one to three cases per 100,000 people that is believed to be the same worldwide. There appears to be no ethnic or racial predisposition to ALS. Prior to the age of 65 or 70, the incidence of ALS is higher in men than in women, but thereafter the gender incidence is equal. ALS has an age distribution that peaks in the seventh to eighth decades. However, ALS can occur in people in their twenties. ALS is most commonly sporadic. Genetic or familial ALS represents only 10 percent of all ALS. (See "Familial amyotrophic lateral sclerosis".)

This topic will review the clinical features of ALS. The epidemiology, diagnosis, and differential diagnosis of ALS are discussed separately. (See "Epidemiology and pathogenesis of amyotrophic lateral sclerosis" and "Diagnosis of amyotrophic lateral sclerosis and other forms of motor neuron disease".)


The clinical hallmark of ALS is the combination of upper and lower motor neuron signs and symptoms.

The upper motor neuron findings of weakness with slowness, hyperreflexia, and spasticity result from degeneration of frontal motor neurons located in the motor strip (Brodman area 4) and their axons traversing the corona radiata, internal capsule, cerebral peduncles, pontine base, medullary pyramids, and the lateral corticospinal tracts of the spinal cord. At autopsy, the dorsolateral area of the spinal cord, the region containing the lateral corticospinal tract, is gliotic and hardened or sclerotic to palpation.

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Literature review current through: Sep 2017. | This topic last updated: Sep 13, 2017.
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