Primary lateral sclerosis
Life span could essentially be normal, although it may be life-limiting, depending on whether it remains as pure PLS or develops into ALS. Within the first four years from developing symptoms, people thought to have PLS can additionally develop lower motor neuron symptoms leading to the diagnosis ALS.
PLS affects the nerve cells that send messages from the brain down the spinal cord and on to the muscles. This causes weakness, especially in the legs, and stiffness in the muscles and joints (known as spasticity). Some people develop weakness and stiffness in the muscles used for speech and swallowing too. Not all symptoms necessarily happen to everyone and they do not usually develop at the same time.
PLS typically affects people aged 35-65 years. There is no cure or treatment for PLS, but symptoms can be managed to improve quality of life.
PLS occurs sporadically in the majority of affected individuals. Sporadic is the term used for cases of the disease where there is no family history. The causes of PLS and related motor neuron diseases ALS and PMA are not known, and research is ongoing. It is thought that a combination of environmental and genetic factors play a part, but it is not currently possible to give a clear answer about the precise triggers. Research of the causes of PLS, ALS and PMA is ongoing.