Doctors have reported the first successful treatment for Huntington’s disease, describing the breakthrough as a major step in tackling one of the most devastating brain disorders.

The disease, which relentlessly kills brain cells, resembles a combination of dementia, Parkinson’s and motor neurone disease.

Huntington’s disease attacks areas of the brain that help to control voluntary (intentional) movement, as well as other areas and people living with the disease develop uncontrollable dance-like movements (chorea) and abnormal body postures, as well as problems with behavior, emotion, thinking, and personality.

Researchers involved in the clinical trial said the results showed that the progression of Huntington’s was slowed by 75 per cent in patients who received the experimental therapy.

The therapy is a form of gene treatment delivered through 12 to 18 hours of delicate brain surgery. Since symptoms of Huntington’s usually appear in people in their 30s or 40s and the disease is often fatal within two decades, researchers believe earlier treatment could even prevent symptoms from emerging.

The new therapy, developed by biotech company uniQure, uses a modified virus to deliver DNA into brain cells. The DNA produces microRNA that disables the faulty instructions responsible for creating the toxic huntingtin protein, which damages and kills neurons.

Data from the trial involving 29 patients indicated that three years after surgery, disease progression had slowed by an average of 75 per cent, measured across cognition, motor function and daily life. The results also showed that brain cells were being preserved, as neurofilament levels – a marker of cell death – were lower than expected.

The Director of the University College London Huntington’s Disease Centre, Prof. Sarah Tabrizi, said the results were spectacular and explained that the decline normally expected in one year would now take four years, potentially giving patients decades of good quality life.

Although the treatment was considered safe, some patients experienced temporary inflammation from the virus, causing headaches and confusion, which either resolved or required steroids.

The researchers believe the benefits should last a lifetime, since brain cells are not naturally replaced like blood or skin cells.