08/23/2011 04:29 pm ET | Updated Oct 22, 2011

Cause Of ALS, Also Known As Lou Gehrig's Disease, Pinpointed By Scientists

Researchers have pinpointed the cause of amyotrophic lateral sclerosis -- most commonly known as ALS, or Lou Gehrig's disease -- a deadly, paralyzing neurodegenerative disease that has puzzled scientists since its discovery.

It all lies in the protein-recycling system of the neurons in the spinal cord and brain. In order for those neurons to function properly, the protein building blocks in cells must be efficiently recycled.

But in ALS, that protein-recycling system is broken -- and the cells are unable to repair themselves, thereby becoming damaged and leading to a breakdown in communication between the muscular system and the brain, according to the Nature study.

As a result, ALS causes muscle weakness that affects mobility and speech, and ultimately results in death, according to the Mayo Clinic. One to three people for every 100,000 people in the world develop ALS.

This discovery brings new hope that a treatment for ALS can be developed, researchers said.

"We can now test for drugs that would regulate this protein pathway or optimize it, so it functions as it should in a normal state," study researcher Dr. Teepu Siddique, M.D., professor of neurology and clinical neurosciences at Northwestern's Feinberg School of Medicine, said in a statement.

Researchers found that this dysfunction of the protein recycling system occurs in all three kinds of ALS -- hereditary, non-hereditary (sporadic) and ALS that targets the brain (ALS/dementia), according to the study. Before, researchers weren't even positive that there was a common disease process for all three kinds of ALS, HealthDay reported.

The discovery could also provide hope for treatments for Parkinson's and Alzheimer's diseases, since they all involve protein build-up, researchers said.

Currently, ALS treatments are only able to slow the progression of ALS -- not reverse the course of the disease, according to the Mayo Clinic. The drug riluzole is the only one approved by the Food and Drug Administration for slowing ALS, and works by lowering levels of a brain chemical messenger called glutamate that's usually at higher levels in people with ALS.

Therapy is also a common course for people with ALS, including physical therapy (to maintain range of motion and muscle strength), occupational therapy (to get used to using a wheelchair or other aid) and speech therapy (because the disease affects the speech muscles, according to the Mayo Clinic).