What is axial ALS?

The term “axial” stands for the body axis of the human body: the trunk. Axial ALS is a special form of ALS in which paresis (paralysis) and myatrophy (muscle atrophy) of the trunk predominate. The trunk is affected by trunk instability, an increased bending posture and the associated gait disturbance, while the extremities are largely preserved in their function. A further characteristic – in addition to the trunk instability – is the restriction of respiratory function.

Human respiration is mainly realized by trunk muscles (diaphragm, rib muscles, abdominal muscles). Patients with axial ALS exhibit respiratory dysfunction, which is characterized by increased respiratory effort (dyspnoea) or insufficient exchange of respiratory gases (accumulation of carbon dioxide resulting in tiredness and fatigue).

In a very rare constellation (affecting less than 2% of all people with ALS), the respiratory muscles are affected first, while the rest of the trunk and the extremities show no paresis. This form of axial ALS is typically diagnosed first by pulmonologists. It typically requires respiratory support early in the course of the disease, as weakness of the respiratory muscles can occur at the onset of ALS. Axial ALS affects less than about 4% of all people with ALS.