University of Edinburgh experts have found a problem with MND patients' nerve cells which could be repaired by repurposing drugs approved for other diseases.
The study has been welcomed by charities including the foundation set up by Scots rugby legend Doddie Weir.
My Name'5 Doddie foundation described it as "a very exciting breakthrough".
More than 1,500 people are diagnosed with the degenerative condition in the UK every year.
There is no known cure and more than half die within two years of diagnosis.
The research found that the damage to nerve cells caused by MND could be repaired by improving the energy levels in mitochondria - the power supply to the motor neurons.
They discovered in human stem cell models of MND, the axon - the long part of the motor neuron cell that connects to the muscle - was shorter than in healthy cells and the movement of the mitochondria, which travel up and down the axons, was impaired.
The scientists showed that this was caused by a defective energy supply from the mitochondria and that by boosting the mitochondria, the axon reverted back to normal.
Dr Arpan Mehta, who led the study at Euan MacDonald Centre for MND research said: "The importance of the axon in motor nerve cells cannot be understated. "Our data provides hope that by restoring the cell's energy source we can protect the axons and their connection to muscle from degeneration. Work is already under way to identify existing licensed drugs that can boost the mitochondria and repair the motor neurons. This will then pave the way to test them in clinical trials."
Craig Stockton, the chief executive of MND Scotland, said the "exciting" results of the research were another piece of the puzzle to finding an effective treatment for the degenerative condition.
"We look forward to seeing if these positive results can be replicated for patients," he said.
"Once researchers have identified a drug they believe could have the desired effect, this treatment could then be fast-tracked for human trials using the pioneering MND-SMART clinical trial platform - into which MND Scotland has invested £1.5m.
"Researchers, clinicians, charities and supporters are all working hard to take us closer to finding a cure and by joining together we'll get to that day even sooner."
The researchers used stem cells taken from people with the C9orf72 gene mutation that causes both MND and frontotemporal dementia. They used the stem cells to generate motor neuron cells in the lab.
The study also used human post-mortem spinal cord tissue from people with MND.
Although the research focused on the people with the commonest genetic cause of MND, the researchers said they were hopeful the results would also apply to other forms of the disease.
The results of the study are now being used to look for existing drugs that boost mitochondrial function.
The study was funded by the Medical Research Council, Motor Neurone Disease Association, Euan MacDonald Centre for MND Research, My Name'5 Doddie Foundation, UK Dementia Research Institute and Anne Rowling Regenerative Neurology Clinic.