Which clinical history findings are characteristic of amyotrophic lateral sclerosis (ALS) (Lou Gehrig disease)?

Updated: Apr 28, 2014
  • Author: Hidehiro Takei, MD; Chief Editor: Adekunle M Adesina, MD, PhD  more...
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The incidence of amyotrophic lateral sclerosis (ALS) increases with age until it peaks around the age of 75 years. In familial ALS, the onset is a decade earlier. Otherwise, familial and sporadic cases are clinically indistinguishable, and thus, a detailed family history and genetic studies are very important in discriminating between these 2 forms.

Approximately two thirds of patients with ALS initially present with focal muscle weakness in the upper or lower limbs (classic Charcot ALS), and approximately one fourth of patients presents with dysarthria, followed by progressive dysphagia (bulbar-onset ALS). Patients with ALS due to C9orf72 mutation present more frequently with bulbar onset; in addition, cognitive involvement is more common. [24]

In ALS with SOD1 mutations, extremity onset, particularly in the legs, is much more common than bulbar onset. About 5% of cases present with respiratory weakness without significant limb or bulbar symptoms. [25]

The flail arm and flail leg variants are initially localized forms with predominantly lower motor neuron (LMN) symptoms. [26] These are characterized by progressive weakness and severe wasting of the upper and lower limbs, bilaterally.

Regardless of the body part that is first affected by ALS disease, weakness and atrophy spread to other parts of body with varying degrees of upper motor neuron (UMN) symptoms (eg, spasticity) and eventually involve the muscles of all 4 extremities and the trunk, as well as bulbar muscles. Rectal and bladder sphincters and oculomotor muscles are usually spared. Sensory examination is usually unremarkable.

Approximately 5% of patients with ALS develop dementia of the frontotemporal type, characterized by behavioral changes with or without language dysfunction.

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