What is ALS?

ALS is a progressive disease of the motor neurons — the nerve cells that control voluntary muscle movement.

Overview

Amyotrophic lateral sclerosis (ALS) affects upper and lower motor neurons. Over time, this can lead to progressive muscle weakness, wasting, stiffness, speech and swallowing problems, and later breathing difficulties.

Common forms of onset

Limb onset

Symptoms begin in an arm or leg. A person may notice dropping objects, weaker grip, tripping, foot drop, or difficulty climbing stairs.

Bulbar onset

Early symptoms involve speech and swallowing: slurred speech, choking, voice changes, difficulty chewing or swallowing liquids.

Related motor neuron disease forms

Progressive muscular atrophy (PMA)

PMA mainly affects lower motor neurons and often presents with weakness, muscle atrophy and fasciculations. Some people may later develop signs of upper motor neuron involvement.

Primary lateral sclerosis (PLS)

PLS mainly affects upper motor neurons. It commonly causes stiffness, spasticity, slow movement and gait problems, and usually progresses more slowly than typical ALS.

Upper and lower motor neurons

Upper motor neuron signs

Increased reflexes, spasticity, stiffness and pathological reflexes.

Lower motor neuron signs

Weakness, muscle wasting, fasciculations and reduced reflexes.

Sources