What is a spastic variant of ALS?

In ALS, paralysis (paresis) and muscle stiffness due to uncontrolled muscle activity (spasticity) must be distinguished. The muscle weakness is generally caused by a degeneration of the motor nerve cells in the spinal cord (second motor neuron). In spastic ALS, this section of the motor nervous system is less affected and largely preserved. As a result, muscle weaknesses are barely detectable. In the spastic variant, the focus is rather on spasticity of the extremities and trunk as well as the tongue and pharynx, which is caused by damage to motor nerve cells in the brain (first motor neuron). Spastic ALS affects a smaller group of people with ALS and is diagnosed in less than 20% of those affected.