Researchers identify mutation in Mirror Motion Syndrome

Severe COVID-19 infections are known to put patients at risk of neurological complications. (AFP)

A new genetic mutation identified by Montreal researchers may be responsible for mirror movement syndrome, according to a study published in the scientific journal Science Advances.

Mirror Motion Syndrome is an inherited neurological disorder that manifests itself in involuntary movements from an early age, mainly in the arms and hands. In affected individuals, the right hand involuntarily reproduces the movements of the left hand and vice versa.

The disorder can also affect the lower limbs but to a lesser extent.

"This makes people much less dexterous than the average person, obviously," said professor Frédéric Charron, who heads the Molecular Biology of Neuronal Development Research Unit at the Clinical Research Institute of Montreal. "If you think about playing billiards, for example, where one hand is not supposed to move at all, and the other hand is supposed to move, there are all sorts of movements that don't go very well."

It is well known that the right side of the brain controls the left side of the body, and vice versa. In a nutshell, mirror movement syndrome occurs when the electrical wire that runs from one side of the brain to the other side of the body splits and takes a diversion to the wrong side, causing these involuntary movements.

Charron, Dr. Myriam Srour of the Montreal Children's Hospital and researchers Sabrina Schlienger and Patricia Yam have identified a new gene and mechanism responsible for this dysfunction.

They were able to reproduce the problem in genetically modified mice in the laboratory. These mice, Charron said, have difficulty moving normally, for example, when asked to walk up a ladder, which they should be able to do quite easily.

The intensity of the problem varies from person to person, but it is easy to imagine that this disorder can greatly interfere with the patients' daily lives, from dressing to playing sports and that it can cause pain in the arms during prolonged activities. For example, the patient may clutch the table with the left hand to prevent it from moving while signing with the right.

"It becomes unbearable for them, at some point, to make this effort constantly," said Charron.

Mirror movement syndrome is a rare disease, but its incidence is somewhat more pronounced in Quebec, possibly because of the founder effect. The new findings are the result of a study of a family that has been affected for four generations.

The identification of the genes involved in the syndrome is an important first step towards rapid and efficient diagnosis. Patients with a rare disease, Charron recalled, often have to wait a long time for a diagnosis.

"It is stressful for them to be told that we don't know exactly what they have," he said. "But it gives them some peace of mind to have a diagnosis, to hear that they have such and such a mutation known to cause mirror movements, that their condition is going to stay like that and that it's not neurodegenerative."

The discovery of this mutation could also one day lead to the development of new therapies that would address the problem before birth. But since mirror movement syndrome is not a fatal disease, Charron said, care would have to be taken to ensure that the consequences of intervention would not be greater than the problem itself.

This report by The Canadian Press was first published in French on May 15, 2023.